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• What are the pros and cons of using manual list iteration vs recursion through fail

  - by magus

  I come up against this all the time, and I'm never sure which way to attack it. Below are two methods for processing some season facts. What I'm trying to work out is whether to use method 1 or 2, and what are the pros and cons of each, especially large amounts of facts. methodone seems wasteful since the facts are available, why bother building a list of them (especially a large list). This must have memory implications too if the list is large enough ? And it doesn't take advantage of Prolog's natural backtracking feature. methodtwo takes advantage of backtracking to do the recursion for me, and I would guess would be much more memory efficient, but is it good programming practice generally to do this? It's arguably uglier to follow, and might there be any other side effects? One problem I can see is that each time fail is called, we lose the ability to pass anything back to the calling predicate, eg. if it was methodtwo(SeasonResults), since we continually fail the predicate on purpose. So methodtwo would need to assert facts to store state. Presumably(?) method 2 would be faster as it has no (large) list processing to do? I could imagine that if I had a list, then methodone would be the way to go.. or is that always true? Might it make sense in any conditions to assert the list to facts using methodone then process them using method two? Complete madness? But then again, I read that asserting facts is a very 'expensive' business, so list handling might be the way to go, even for large lists? Any thoughts? Or is it sometimes better to use one and not the other, depending on (what) situation? eg. for memory optimisation, use method 2, including asserting facts and, for speed use method 1? season(spring). season(summer). season(autumn). season(winter). % Season handling showseason(Season) :- atom_length(Season, LenSeason), write('Season Length is '), write(LenSeason), nl. % ------------------------------------------------------------- % Method 1 - Findall facts/iterate through the list and process each %-------------------------------------------------------------- % Iterate manually through a season list lenseason([]). lenseason([Season|MoreSeasons]) :- showseason(Season), lenseason(MoreSeasons). % Findall to build a list then iterate until all done methodone :- findall(Season, season(Season), AllSeasons), lenseason(AllSeasons), write('Done'). % ------------------------------------------------------------- % Method 2 - Use fail to force recursion %-------------------------------------------------------------- methodtwo :- % Get one season and show it season(Season), showseason(Season), % Force prolog to backtrack to find another season fail. % No more seasons, we have finished methodtwo :- write('Done').

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• Pointers to class fields

  - by newbie_cpp

  My task is as follows : Using pointers to class fields, create menu allowing selection of ice, that Person can buy in Ice shop. Buyer will be charged with waffel and ice costs. Selection of ice and charging buyers account must be shown in program. Here's my Person class : #include <iostream> using namespace std; class Iceshop { const double waffel_price = 1; public: } class Person { static int NUMBER; char* name; int age; const int number; double plus, minus; public: class Account { int number; double resources; public: Account(int number, double resources) : number(number), resources(resources) {} } Person(const char* n, int age) : name(strcpy(new char[strlen(n)+1],n)), number(++NUMBER), plus(0), minus(0), age(age) {} Person::~Person(){ cout << "Destroying resources" << endl; delete [] name; } friend void show(Person &p); int* take_age(){ return &age; } char* take_name(){ return name; } void init(char* n, int a) { name = n; age = a; } Person& remittance(double d) { plus += d; return *this; } Person& paycheck(double d) { minus += d; return *this; } Account* getAccount(); }; int Person:: Person::Account* Person::getAccount() { return new Account(number, plus - minus); } void Person::Account::remittance(double d){ resources = resources + d; } void Person::Account::paycheck(double d){ resources = resources - d; } void show(Person *p){ cout << "Name: " << p->take_name() << "," << "age: " << p->take_age() << endl; } int main(void) { Person *p = new Person; p->init("Mary", 25); show(p); p->remittance(100); system("PAUSE"); return 0; } How to start this task ? Where and in what form should I store menu options ?

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• Asp.net Mvc - Kigg: Maintain User object in HttpContext.Items between requests.

  - by Pickels

  Hallo, first I want to say that I hope this doesn't look like I am lazy but I have some trouble understanding a piece of code from the following project. http://kigg.codeplex.com/ I was going through the source code and I noticed something that would be usefull for my own little project I am making. In their BaseController they have the following code: private static readonly Type CurrentUserKey = typeof(IUser); public IUser CurrentUser { get { if (!string.IsNullOrEmpty(CurrentUserName)) { IUser user = HttpContext.Items[CurrentUserKey] as IUser; if (user == null) { user = AccountRepository.FindByClaim(CurrentUserName); if (user != null) { HttpContext.Items[CurrentUserKey] = user; } } return user; } return null; } } This isn't an exact copy of the code I adjusted it a little to my needs. This part of the code I still understand. They store their IUser in HttpContext.Items. I guess they do it so that they don't have to call the database eachtime they need the User object. The part that I don't understand is how they maintain this object in between requests. If I understand correctly the HttpContext.Items is a per request cache storage. So after some more digging I found the following code. internal static IDictionary<UnityPerWebRequestLifetimeManager, object> GetInstances(HttpContextBase httpContext) { IDictionary<UnityPerWebRequestLifetimeManager, object> instances; if (httpContext.Items.Contains(Key)) { instances = (IDictionary<UnityPerWebRequestLifetimeManager, object>) httpContext.Items[Key]; } else { lock (httpContext.Items) { if (httpContext.Items.Contains(Key)) { instances = (IDictionary<UnityPerWebRequestLifetimeManager, object>) httpContext.Items[Key]; } else { instances = new Dictionary<UnityPerWebRequestLifetimeManager, object>(); httpContext.Items.Add(Key, instances); } } } return instances; } This is the part where some magic happens that I don't understand. I think they use Unity to do some dependency injection on each request? In my project I am using Ninject and I am wondering how I can get the same result. I guess InRequestScope in Ninject is the same as UnityPerWebRequestLifetimeManager? I am also wondering which class/method they are binding to which interface? Since the HttpContext.Items get destroyed each request how do they prevent losing their user object? Anyway it's kinda a long question so I am gradefull for any push in the right direction. Kind regards, Pickels

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• Can I avoid a threaded UDP socket in Python dropping data?

  - by 666craig

  First off, I'm new to Python and learning on the job, so be gentle! I'm trying to write a threaded Python app for Windows that reads data from a UDP socket (thread-1), writes it to file (thread-2), and displays the live data (thread-3) to a widget (gtk.Image using a gtk.gdk.pixbuf). I'm using queues for communicating data between threads. My problem is that if I start only threads 1 and 3 (so skip the file writing for now), it seems that I lose some data after the first few samples. After this drop it looks fine. Even by letting thread 1 complete before running thread 3, this apparent drop is still there. Apologies for the length of code snippet (I've removed the thread that writes to file), but I felt removing code would just prompt questions. Hope someone can shed some light :-) import socket import threading import Queue import numpy import gtk gtk.gdk.threads_init() import gtk.glade import pygtk class readFromUDPSocket(threading.Thread): def __init__(self, socketUDP, readDataQueue, packetSize, numScans): threading.Thread.__init__(self) self.socketUDP = socketUDP self.readDataQueue = readDataQueue self.packetSize = packetSize self.numScans = numScans def run(self): for scan in range(1, self.numScans + 1): buffer = self.socketUDP.recv(self.packetSize) self.readDataQueue.put(buffer) self.socketUDP.close() print 'myServer finished!' class displayWithGTK(threading.Thread): def __init__(self, displayDataQueue, image, viewArea): threading.Thread.__init__(self) self.displayDataQueue = displayDataQueue self.image = image self.viewWidth = viewArea[0] self.viewHeight = viewArea[1] self.displayData = numpy.zeros((self.viewHeight, self.viewWidth, 3), dtype=numpy.uint16) def run(self): scan = 0 try: while True: if not scan % self.viewWidth: scan = 0 buffer = self.displayDataQueue.get(timeout=0.1) self.displayData[:, scan, 0] = numpy.fromstring(buffer, dtype=numpy.uint16) self.displayData[:, scan, 1] = numpy.fromstring(buffer, dtype=numpy.uint16) self.displayData[:, scan, 2] = numpy.fromstring(buffer, dtype=numpy.uint16) gtk.gdk.threads_enter() self.myPixbuf = gtk.gdk.pixbuf_new_from_data(self.displayData.tostring(), gtk.gdk.COLORSPACE_RGB, False, 8, self.viewWidth, self.viewHeight, self.viewWidth * 3) self.image.set_from_pixbuf(self.myPixbuf) self.image.show() gtk.gdk.threads_leave() scan += 1 except Queue.Empty: print 'myDisplay finished!' pass def quitGUI(obj): print 'Currently active threads: %s' % threading.enumerate() gtk.main_quit() if __name__ == '__main__': # Create socket (IPv4 protocol, datagram (UDP)) and bind to address socketUDP = socket.socket(socket.AF_INET, socket.SOCK_DGRAM) host = '192.168.1.5' port = 1024 socketUDP.bind((host, port)) # Data parameters samplesPerScan = 256 packetsPerSecond = 1200 packetSize = 512 duration = 1 # For now, set a fixed duration to log data numScans = int(packetsPerSecond * duration) # Create array to store data data = numpy.zeros((samplesPerScan, numScans), dtype=numpy.uint16) # Create queue for displaying from readDataQueue = Queue.Queue(numScans) # Build GUI from Glade XML file builder = gtk.Builder() builder.add_from_file('GroundVue.glade') window = builder.get_object('mainwindow') window.connect('destroy', quitGUI) view = builder.get_object('viewport') image = gtk.Image() view.add(image) viewArea = (1200, samplesPerScan) # Instantiate & start threads myServer = readFromUDPSocket(socketUDP, readDataQueue, packetSize, numScans) myDisplay = displayWithGTK(readDataQueue, image, viewArea) myServer.start() myDisplay.start() gtk.gdk.threads_enter() gtk.main() gtk.gdk.threads_leave() print 'gtk.main finished!'

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• Helping linqtosql datacontext use implicit conversion between varchar column in the database and tab

  - by user213256

  I am creating an mssql database table, "Orders", that will contain a varchar(50) field, "Value" containing a string that represents a slightly complex data type, "OrderValue". I am using a linqtosql datacontext class, which automatically types the "Value" column as a string. I gave the "OrderValue" class implicit conversion operators to and from a string, so I can easily use implicit conversion with the linqtosql classes like this: // get an order from the orders table MyDataContext db = new MyDataContext(); Order order = db.Orders(o => o.id == 1); // use implicit converstion to turn the string representation of the order // value into the complex data type. OrderValue value = order.Value; // adjust one of the fields in the complex data type value.Shipping += 10; // use implicit conversion to store the string representation of the complex // data type back in the linqtosql order object order.Value = value; // save changes db.SubmitChanges(); However, I would really like to be able to tell the linqtosql class to type this field as "OrderValue" rather than as "string". Then I would be able to avoid complex code and re-write the above as: // get an order from the orders table MyDataContext db = new MyDataContext(); Order order = db.Orders(o => o.id == 1); // The Value field is already typed as the "OrderValue" type rather than as string. // When a string value was read from the database table, it was implicity converted // to "OrderValue" type. order.Value.Shipping += 10; // save changes db.SubmitChanges(); In order to achieve this desired goal, I looked at the datacontext designer and selected the "Value" field of the "Order" table. Then, in properties, I changed "Type" to "global::MyApplication.OrderValue". The "Server Data Type" property was left as "VarChar(50) NOT NULL" The project built without errors. However, when reading from the database table, I was presented with the following error message: Could not convert from type 'System.String' to type 'MyApplication.OrderValue'. at System.Data.Linq.DBConvert.ChangeType(Object value, Type type) at Read_Order(ObjectMaterializer1 ) at System.Data.Linq.SqlClient.ObjectReaderCompiler.ObjectReader2.MoveNext() at System.Linq.Buffer1..ctor(IEnumerable1 source) at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source) at Example.OrdersProvider.GetOrders() at ... etc From the stack trace, I believe this error is happening while reading the data from the table. When presented with converting a string to my custom data type, even though the implicit conversion operators are present, the DBConvert class gets confused and throws an error. Is there anything I can do to help it not get confused and do the implicit conversion? Thanks in advance, and apologies if I have posted in the wrong forum. cheers / Ben

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• initializing a vector of custom class in c++

  - by Flamewires

  Hey basically Im trying to store a "solution" and create a vector of these. The problem I'm having is with initialization. Heres my class for reference class Solution { private: // boost::thread m_Thread; int itt_found; int dim; pfn_fitness f; double value; std::vector<double> x; public: Solution(size_t size, int funcNo) : itt_found(0), x(size, 0.0), value(0.0), dim(30), f(Eval_Functions[funcNo]) { for (int i = 1; i < (int) size; i++) { x[i] = ((double)rand()/((double)RAND_MAX))*maxs[funcNo]; } } Solution() : itt_found(0), x(31, 0.0), value(0.0), dim(30), f(Eval_Functions[1]) { for (int i = 1; i < 31; i++) { x[i] = ((double)rand()/((double)RAND_MAX))*maxs[1]; } } Solution operator= (Solution S) { x = S.GetX(); itt_found = S.GetIttFound(); dim = S.GetDim(); f = S.GetFunc(); value = S.GetValue(); return *this; } void start() { value = f (dim, x); } /* plus additional getter/setter methods*/ } Solution S(30, 1) or Solution(2, 5) work and initalizes everything, but I need X of these solution objects. std::vector<Solution> Parents(X) will create X solutions with the default constructor and i want to construct using the (int, int) constructor. Is there any easy(one liner?) way to do this? Or would i have to do something like: size_t numparents = 10; vector<Solution> Parents; Parents.reserve(numparents); for (int i = 0; i<(int)numparents; i++) { Solution S(31, 0); Parents.push_back(S); }

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• Sorted sets and comparators

  - by Jack

  Hello, I'm working with a TreeSetthat is meant to store pathfind locations used during the execution of a A* algorithm. Basically until there are "open" elements (still to be exhaustively visited) the neighbours of every open element are taken into consideration and added to a SortedSetthat keeps them ordered by their cost and heuristic cost. This means that I have a class like: public class PathTileInfo implements Comparable<PathTileInfo> { int cost; int hCost; final int x, y; @Override public int compareTo(PathTileInfo t2) { int c = cost + hCost; int c2 = t2.cost + t2.hCost; int costComp = c < c2 ? -1 : (c > c2 ? 1: 0); return costComp != 0 ? costComp : (x < t2.x || y < t2.y ? -1 : (x > t2.x || y > t2.y ? 1 : 0)); } @Override public boolean equals(Object o2) { if (o2 instanceof PathTileInfo) { PathTileInfo i = (PathTileInfo)o2; return i.cost + i.hCost == cost + hCost && x == i.x && y == i.y; } return false; } } In this way first the total cost is considered, then, since a total ordering is needed (consistency with equals) a ordering according to the x,y coordinate is taken into account. This should work but simply it doesn't, if I iterate over the TreeSet during the algorithm execution like in for (PathTileInfo t : openSet) System.out.print("("+t.x+","+t.y+","+(t.cost+t.hCost)+") "); I get results in which the right ordering is not kept, eg: (7,7,6) (7,6,7) (6,8,6) (6,6,7) (5,8,7) (5,7,7) (6,7,6) (6,6,7) (6,5,7) (5,7,7) (5,5,8) (4,7,7) (4,6,8) (4,5,8) is there something subtle I am missing? Thanks!

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• Maximum nametable char count exceeded

  - by doc

  I'm having issues with the maximum nametable char count quota, I followed a couple of answers here and it solved the problem for a while, but now I'm having the same issue. My Server side config is as follows: <system.serviceModel> <bindings> <netTcpBinding> <binding name="GenericBinding" maxBufferPoolSize="2147483647" maxBufferSize="2147483647" maxReceivedMessageSize="2147483647"> <readerQuotas maxDepth="2147483647" maxStringContentLength="2147483647" maxArrayLength="2147483647" maxBytesPerRead="2147483647" maxNameTableCharCount="2147483647" /> <security mode="None" /> </binding> </netTcpBinding> </bindings> <behaviors> <serviceBehaviors> <behavior> <serviceMetadata httpGetEnabled="false" /> <serviceDebug includeExceptionDetailInFaults="true" /> <dataContractSerializer maxItemsInObjectGraph="1000000" /> </behavior> </serviceBehaviors> </behaviors> <services> <service name="REMWCF.RemWCFSvc"> <endpoint address="" binding="netTcpBinding" contract="REMWCF.IRemWCFSvc" bindingConfiguration="GenericBinding" /> <endpoint address="mex" binding="mexTcpBinding" contract="IMetadataExchange" /> <host> <baseAddresses> <add baseAddress="net.tcp://localhost:9081/RemWCFSvc" /> </baseAddresses> </host> </service> </services> </system.serviceModel> I also have the same tcp binding on the devenv configuration. Have I reached the limit of contracts supported? Is there a way to turn off that quota? EDIT Error Message: Error: Cannot obtain Metadata from net.tcp://localhost:9081/RemWCFSvc/mex If this is a Windows (R) Communication Foundation service to which you have access, please check that you have enabled metadata publishing at the specified address. For help enabling metadata publishing, please refer to the MSDN documentation at http://go.microsoft.com/fwlink/?LinkId=65455.WS-Metadata Exchange Error URI: net.tcp://localhost:9081/RemWCFSvc/mex Metadata contains a reference that cannot be resolved: 'net.tcp://localhost:9081/RemWCFSvc/mex'. There is an error in the XML document. The maximum nametable character count quota (16384) has been exceeded while reading XML data. The nametable is a data structure used to store strings encountered during XML processing - long XML documents with non-repeating element names, attribute names and attribute values may trigger this quota. This quota may be increased by changing the MaxNameTableCharCount property on the XmlDictionaryReaderQuotas object used when creating the XML reader. I'm getting that error when trying to run the WCF (which is hosted in a windows service app).

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• Drill down rss reader iphone

  - by bing

  Hi everyone, I have made a simple rss reader. The app loads an xml atom file in an array. Now I have added categories to my atom feed, which are first loaded in the array What is the best way to add drill down functionality programmatically. Now only the categories are loaded into the array and displayed. This is the implementation code ..... loading xml file <snip> ..... - (void)parserDidStartDocument:(NSXMLParser *)parser { NSLog(@"found file and started parsing"); } - (void)parser:(NSXMLParser *)parser parseErrorOccurred:(NSError *)parseError { NSString * errorString = [NSString stringWithFormat:@"Unable to download story feed from web site (Error code %i )", [parseError code]]; NSLog(@"error parsing XML: %@", errorString); UIAlertView * errorAlert = [[UIAlertView alloc] initWithTitle:@"Error loading content" message:errorString delegate:self cancelButtonTitle:@"OK" otherButtonTitles:nil]; [errorAlert show]; } - (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict{ //NSLog(@"found this element: %@", elementName); currentElement = [elementName copy]; if ([elementName isEqualToString:@"entry"]) { // clear out our story item caches... Categoryentry = [[NSMutableDictionary alloc] init]; currentID = [[NSMutableString alloc] init]; currentTitle = [[NSMutableString alloc] init]; currentSummary = [[NSMutableString alloc] init]; currentContent = [[NSMutableString alloc] init]; } } - (void)parser:(NSXMLParser *)parser didEndElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName{ //NSLog(@"ended element: %@", elementName); if ([elementName isEqualToString:@"entry"]) { // save values to an entry, then store that item into the array... [Categoryentry setObject:currentTitle forKey:@"title"]; [Categoryentry setObject:currentID forKey:@"id"]; [Categoryentry setObject:currentSummary forKey:@"summary"]; [Categoryentry setObject:currentContent forKey:@"content"]; [categories addObject:[Categoryentry copy]]; NSLog(@"adding category: %@", currentTitle); } } - (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string{ //NSLog(@"found characters: %@", string); // save the characters for the current item... if ([currentElement isEqualToString:@"title"]) { [currentTitle appendString:string]; } else if ([currentElement isEqualToString:@"id"]) { [currentID appendString:string]; } else if ([currentElement isEqualToString:@"summary"]) { [currentSummary appendString:string]; } else if ([currentElement isEqualToString:@"content"]) { [currentContent appendString:string]; } } - (void)parserDidEndDocument:(NSXMLParser *)parser { [activityIndicator stopAnimating]; [activityIndicator removeFromSuperview]; NSLog(@"all done!"); NSLog(@"categories array has %d entries", [categories count]); [newsTable reloadData]; }

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• Adding Insert Row in tableView

  - by user333624

  Hello everyone, I have a tableView that loads its data directly from a Core Data table with a NSFetchedResultsController. I'm not using an intermediate NSMutableArray to store the objects from the fetch results; I basically implemented inside my UITableViewController the protocol method numberOfRowsInSection and it returns the numberOfObjects inside a NSFetchedResultsSectionInfo. id <NSFetchedResultsSectionInfo> sectionInfo = [[fetchedResultsController sections] objectAtIndex:section]; and then I configure the cell content by implementing configureCell:atIndexPath and retrieving object info from the fetchedResultController but right now I have a generic configuration for any object (to avoid complications) cell.textLabel.text = @"categoria"; I also have a NavigationBar with a custom edit button at the right that loads my own selector called customSetEditing. What I'm trying to accomplish is to load an "Insert Cell" at the beginning of the tableView so when I tap it, it creates a new record. This last part is easy to implement the problem is that I dont's seem to be able to load the insert row or any row when I tap on the navigation bar edit button. this is the code for my customSetEditing: - (void) customSetEditing { [super setEditing:YES animated:YES]; [self.tableView setEditing:YES animated:YES]; [[self tableView] beginUpdates]; //[[self tableView] beginUpdates]; UIBarButtonItem *customDoneButtonItem = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemDone target:self action:@selector(customDone)]; [self.navigationItem.rightBarButtonItem release]; self.navigationItem.rightBarButtonItem = customDoneButtonItem; //[categoriasArray insertObject:[NSNull null] atIndex:0]; NSMutableArray *indexPaths = [[NSMutableArray alloc] initWithObjects:[NSIndexPath indexPathForRow:0 inSection:0],nil ]; [self.tableView insertRowsAtIndexPaths:indexPaths withRowAnimation:UITableViewRowAnimationTop]; //[indexPaths release]; [self.tableView reloadData];} Before adding the:[self.tableView reloadData]; I was getting an out of bounds error plus a program crash and although the program is not crashing it is not loading anything. I have seen many examples of similar situations in stackoverflow (by the way is an excellent forum with very helpful and nice people) none of the examples seems to work for me. Any ideas?

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• How to discover classes with [Authorize] attributes using Reflection in C#? (or How to build Dynamic

  - by Pretzel

  Maybe I should back-up and widen the scope before diving into the title question... I'm currently writing a web app in ASP.NET MVC 1.0 (although I do have MVC 2.0 installed on my PC, so I'm not exactly restricted to 1.0) -- I've started with the standard MVC project which has your basic "Welcome to ASP.NET MVC" and shows both the [Home] tab and [About] tab in the upper-right corner. Pretty standard, right? I've added 4 new Controller classes, let's call them "Astronomer", "Biologist", "Chemist", and "Physicist". Attached to each new controller class is the [Authorize] attribute. For example, for the BiologistController.cs [Authorize(Roles = "Biologist,Admin")] public class BiologistController : Controller { public ActionResult Index() { return View(); } } These [Authorize] tags naturally limit which user can access different controllers depending on Roles, but I want to dynamically build a Menu at the top of my website in the Site.Master Page based on the Roles the user is a part of. So for example, if JoeUser was a member of Roles "Astronomer" and "Physicist", the navigation menu would say: [Home] [Astronomer] [Physicist] [About] And naturally, it would not list links to "Biologist" or "Chemist" controller Index page. Or if "JohnAdmin" was a member of Role "Admin", links to all 4 controllers would show up in the navigation bar. Ok, you prolly get the idea... Starting with the answer from this StackOverflow topic about Dynamic Menu building in ASP.NET, I'm trying to understand how I would fully implement this. (I'm a newbie and need a little more guidance, so please bare with me.) The answer proposes Extending the Controller class (call it "ExtController") and then have each new WhateverController inherit from ExtController. My conclusion is that I would need to use Reflection in this ExtController Constructor to determine which Classes and Methods have [Authorize] attributes attached to them to determine the Roles. Then using a Static Dictionary, store the Roles and Controllers/Methods in key-value pairs. I imagine it something like this: public class ExtController : Controller { protected static Dictionary<Type,List<string>> ControllerRolesDictionary; protected override void OnActionExecuted(ActionExecutedContext filterContext) { // build list of menu items based on user's permissions, and add it to ViewData IEnumerable<MenuItem> menu = BuildMenu(); ViewData["Menu"] = menu; } private IEnumerable<MenuItem> BuildMenu() { // Code to build a menu SomeRoleProvider rp = new SomeRoleProvider(); foreach (var role in rp.GetRolesForUser(HttpContext.User.Identity.Name)) { } } public ExtController() { // Use this.GetType() to determine if this Controller is already in the Dictionary if (!ControllerRolesDictionary.ContainsKey(this.GetType())) { // If not, use Reflection to add List of Roles to Dictionary // associating with Controller } } } Is this doable? If so, how do I perform Reflection in the ExtController constructor to discover the [Authorize] attribute and related Roles (if any) ALSO! Feel free to go out-of-scope on this question and suggest an alternate way of solving this "Dynamic Site.Master Menu based on Roles" problem. I'm the first to admit that this may not be the best approach.

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• How can a button click method find out which item is selected in a ListView?

  - by Ian Bayley

  I have a single screen with a bank of buttons below a ListView. Entries on the ListView light up in orange when I scroll so I assume that are selected. When I then press the "Delete" button I want the onClickListener to remove the currently selected entry. But getSelectedItemPosition() always gives me -1. If I can't hope to use the GUI controls in this way, please give me another way of getting the same result. I have even tried setting the onClickListener of the List View to store the index before the button is pressed (in case pressing the button unselects the entry) but even that is always -1 it seems. Here's the code (without the modification which didn't work) package com.bayley; import android.app.Activity; import android.os.Bundle; import android.view.View; import android.widget.ArrayAdapter; import android.widget.Button; import android.widget.EditText; import android.widget.ListView; import java.util.ArrayList; /** * * @author p0074564 */ public class September extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle icicle) { super.onCreate(icicle); setContentView(R.layout.main); final ListView myListView = (ListView) findViewById(R.id.myListView); Button addButton = (Button) findViewById(R.id.AddButton); Button deleteButton = (Button) findViewById(R.id.DeleteButton); final EditText editText = (EditText) findViewById(R.id.myEditText); final ArrayList<String> todoItems = new ArrayList<String>(); todoItems.add("Monday"); todoItems.add("Tuesday"); todoItems.add("Wednesday"); final ArrayAdapter<String> aa = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, todoItems); myListView.setAdapter(aa); addButton.setOnClickListener(new Button.OnClickListener() { public void onClick(View v) { todoItems.add(editText.getText().toString()); aa.notifyDataSetChanged(); } }); deleteButton.setOnClickListener(new Button.OnClickListener() { public void onClick(View v) { // always returns -1 unfortunately ie nothing is ever selected int index = myListView.getSelectedItemPosition(); if (index >= 0) { todoItems.remove(index); } aa.notifyDataSetChanged(); } }); } }

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• IPhone Development Profile Expired

  - by theiphoneguy

  I really combed this site and others. I read and re-read the related links here and the Apple docs. I'm sorry, but either I am obviously missing something right under my nose, or this Apple profile/certificate stuff is a bit convoluted. Here it is: I have a product in the App Store. I have updated it several times and users like it. My development profile recently expired just when I was improving the app for its next release. I can run the app in the simulator. I can compile and put the distribution build on my iPhone just fine. I went to the Apple portal and renewed the development profile. I downloaded it and installed it in Xcode. I see it in the Organize window. I see it on my iPhone. I CANNOT put the debug build on my iPhone to debug or run with Instruments. The message is that either there is not a valid signed profile or it is untrusted. I subsequently tried to download and install the certificate to my Mac's keychain. Still no success. I checked the code signing section of Project settings and also for the target and the root. All appears to indicate that it is using the expected development profile for debug. Yes, I had deleted the old profile from my iPhone, from the Organizer. I cleaned the Xcode cache and all targets. I have done all of this several times and in varying sequences to try to cover every possibility. I am ready to do anything to be able to debug with Instruments in order to check for leaks or high memory usage. Even though the distribution compile runs fine on my iPhone and plays well with other running processes, I will not release anything without a leaks/memory test. Any ideas will be appreciated. If I missed something obvious, please forgive me - it was not due to just posting a question without searching for similar postings. Thanks!

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• jQuery slider onChange auto submit form

  - by bikey77

  I'm using a jQuery slider as a price range selector in a form. I'd like to have the form submit automatically when one of the values has been changed. I used a couple of examples I found on SO but they didn't work with my code. <form action="itemlist.php" method="post" enctype="application/x-www-form-urlencoded" name="priceform" id="priceform" target="_self"> <div id="slider-holder"> Prices: From <span id="pricefromlabel">100 &#8364;</span> To <span id="pricetolabel">500 &#8364;</span> <input type="hidden" id="pricefrom" name="pricefrom" value="100" /> <input type="hidden" id="priceto" name="priceto" value="500" /> <div id="slider-range"></div> <input name="Search" type="submit" value="Search" /> </div> </form> This is the code that displays the values of the slider and updates 2 hidden form fields I use to store the prices in order to submit: <script> $(function() { $("#slider-range" ).slider({ range: true, min: 0, max: 1000, values: [ <?=$minprice?>, <?=$maxprice?> ], start: function (event, ui) { event.stopPropagation(); }, slide: function( event, ui ) { $( "#pricefrom" ).val(ui.values[0]); $( "#priceto" ).val(ui.values[1]); $( "#pricefromlabel" ).html(ui.values[0] + ' &euro;'); $( "#pricetolabel" ).html(ui.values[1] + ' &euro;'); } }); return false; }); </script> I've tried adding this code as well as an data-autosubmit="true" attribute to the div but no result. $(function() { $('[data-autosubmit="true"]').change(function() { parentForm = $(this).('#priceform'); clearTimeout(submitTimeout); submitTimeout = setTimeout(function() { parentForm.submit() }, 100); }); I've also tried adding a $.post() event to the slider but I'm not very good with jQuery so I'm probably doing it wrong. Any help will be appreciated.

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• What IPC method should I use between Firefox extension and C# code running on the same machine?

  - by Rory

  I have a question about how to structure communication between a (new) Firefox extension and existing C# code. The firefox extension will use configuration data and will produce other data, so needs to get the config data from somewhere and save it's output somewhere. The data is produced/consumed by existing C# code, so I need to decide how the extension should interact with the C# code. Some pertinent factors: It's only running on windows, in a relatively controlled corporate environment. I have a windows service running on the machine, built in C#. Storing the data in a local datastore (like sqlite) would be useful for other reasons. The volume of data is low, e.g. 10kb of uncompressed xml every few minutes, and isn't very 'chatty'. The data exchange can be asynchronous for the most part if not completely. As with all projects, I have limited resources so want an option that's relatively easy. It doesn't have to be ultra-high performance, but shouldn't add significant overhead. I'm planning on building the extension in javascript (although could be convinced otherwise if really necessary) Some options I'm considering: use an XPCOM to .NET/COM bridge use a sqlite db: the extension would read from and save to it. The c# code would run in the service, populating the db and then processing data created by the service. use TCP sockets to communicate between the extension and the service. Let the service manage a local data store. My problem with (1) is I think this will be tricky and not so easy. But I could be completely wrong? The main problem I see with (2) is the locking of sqlite: only a single process can write data at a time so there'd be some blocking. However, it would be nice generally to have a local datastore so this is an attractive option if the performance impact isn't too great. I don't know whether (3) would be particularly easy or hard ... or what approach to take on the protocol: something custom or http. Any comments on these ideas or other suggestions? UPDATE: I was planning on building the extension in javascript rather than c++

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• C++ vector and segmentation faults

  - by Headspin

  I am working on a simple mathematical parser. Something that just reads number = 1 + 2; I have a vector containing these tokens. They store a type and string value of the character. I am trying to step through the vector to build an AST of these tokens, and I keep getting segmentation faults, even when I am under the impression my code should prevent this from happening. Here is the bit of code that builds the AST: struct ASTGen { const vector<Token> &Tokens; unsigned int size, pointer; ASTGen(const vector<Token> &t) : Tokens(t), pointer(0) { size = Tokens.size() - 1; } unsigned int next() { return pointer + 1; } Node* Statement() { if(next() <= size) { switch(Tokens[next()].type) { case EQUALS : Node* n = Assignment_Expr(); return n; } } advance(); } void advance() { if(next() <= size) ++pointer; } Node* Assignment_Expr() { Node* lnode = new Node(Tokens[pointer], NULL, NULL); advance(); Node* n = new Node(Tokens[pointer], lnode, Expression()); return n; } Node* Expression() { if(next() <= size) { advance(); if(Tokens[next()].type == SEMICOLON) { Node* n = new Node(Tokens[pointer], NULL, NULL); return n; } if(Tokens[next()].type == PLUS) { Node* lnode = new Node(Tokens[pointer], NULL, NULL); advance(); Node* n = new Node(Tokens[pointer], lnode, Expression()); return n; } } } }; ... ASTGen AST(Tokens); Node* Tree = AST.Statement(); cout << Tree->Right->Data.svalue << endl; I can access Tree->Data.svalue and get the = Node's token info, so I know that node is getting spawned, and I can also get Tree->Left->Data.svalue and get the variable to the left of the = I have re-written it many times trying out different methods for stepping through the vector, but I always get a segmentation fault when I try to access the = right node (which should be the + node) Any help would be greatly appreciated.

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• ASP.Net / MySQL : Translating content into several languages

  - by philwilks

  I have an ASP.Net website which uses a MySQL database for the back end. The website is an English e-commerce system, and we are looking at the possibility of translating it into about five other languages (French, Spanish etc). We will be getting human translators to perform the translation - we've looked at automated services but these aren't good enough. The static text on the site (e.g. headings, buttons etc) can easily be served up in multiple languages via .Net's built in localization features (resx files etc). The thing that I'm not so sure about it how best to store and retrieve the multi-language content in the database. For example, there is a products table that includes these fields... productId (int) categoryId (int) title (varchar) summary (varchar) description (text) features (text) The title, summary, description and features text would need to be available in all the different languages. Here are the two options that I've come up with... Create additional field for each language For example we could have titleEn, titleFr, titleEs etc for all the languages, and repeat this for all text columns. We would then adapt our code to use the appropriate field depending on the language selected. This feels a bit hacky, and also would lead to some very large tables. Also, if we wanted to add additional languages in the future it would be time consuming to add even more columns. Use a lookup table We could create a new table with the following format... textId | languageId | content ------------------------------- 10 | EN | Car 10 | FR | Voiture 10 | ES | Coche 11 | EN | Bike 11 | FR | Vélo We'd then adapt our products table to reference the appropriate textId for the title, summary, description and features instead of having the text stored in the product table. This seems much more elegant, but I can't think of a simple way of getting this data out of the database and onto the page without using complex SQL statements. Of course adding new languages in the future would be very simple compared to the previous option. I'd be very grateful for any suggestions about the best way to achieve this! Is there any "best practice" guidance out there? Has anyone done this before?

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• How to send a Java integer in four bytes to another application?

  - by user1468729

  public void routeMessage(byte[] data, int mode) { logger.debug(mode); logger.debug(Integer.toBinaryString(mode)); byte[] message = new byte[8]; ByteBuffer byteBuffer = ByteBuffer.allocate(4); ByteArrayOutputStream baoStream = new ByteArrayOutputStream(); DataOutputStream doStream = new DataOutputStream(baoStream); try { doStream.writeInt(mode); } catch (IOException e) { logger.debug("Error converting mode from integer to bytes.", e); return; } byte [] bytes = baoStream.toByteArray(); bytes[0] = (byte)((mode >>> 24) & 0x000000ff); bytes[1] = (byte)((mode >>> 16) & 0x000000ff); bytes[2] = (byte)((mode >>> 8) & 0x00000ff); bytes[3] = (byte)(mode & 0x000000ff); //bytes = byteBuffer.array(); for (byte b : bytes) { logger.debug(b); } for (int i = 0; i < 4; i++) { //byte tmp = (byte)(mode >> (32 - ((i + 1) * 8))); message[i] = bytes[i]; logger.debug("mode, " + i + ": " + Integer.toBinaryString(message[i])); message[i + 4] = data[i]; } broker.routeMessage(message); } I've tried different ways (as you can see from the commented code) to convert the mode to four bytes to send it via a socket to another application. It works well with integers up to 127 and then again with integers over 256. I believe it has something to do with Java types being signed but don't seem to get it to work. Here are some examples of what the program prints. 127 1111111 0 0 0 127 mode, 0: 0 mode, 1: 0 mode, 2: 0 mode, 3: 1111111 128 10000000 0 0 0 -128 mode, 0: 0 mode, 1: 0 mode, 2: 0 mode, 3: 11111111111111111111111110000000 211 11010011 0 0 0 -45 mode, 0: 0 mode, 1: 0 mode, 2: 0 mode, 3: 11111111111111111111111111010011 306 100110010 0 0 1 50 mode, 0: 0 mode, 1: 0 mode, 2: 1 mode, 3: 110010 How is it suddenly possible for a byte to store 32 bits? How could I fix this?

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• Calling managed code from unmanaged win32 assembly dll - crash

  - by JustGreg

  I'm developing a serial port dll in win32 assembly (MASM32). It has its own thread checking multiple events and at a specified buffer treshold it'd notify the managed main application by calling a callback function. It just a call with no arguments/return value. At startup the main application stores the callback function's address by calling a function in the dll: pCallBackFunction dd 0 SetCallBackPointer proc pcb:DWORD mov eax, pcb mov pCallBackFunction, eax call DWORD ptr pCallBackFunction ; verify it immediately ret SetCallBackPointer endp The upper function immediately calls back the managed application callback routine for verification purposes. It is working fine. However, when I place the call instruction to other functions in the dll it crashes the application. It doesn't matter if the call is in a simple function or in the threadproc of the dll. For example: OpenPort proc pn:byte,br:dword, inputbuffersize: dword, outputbuffersize:dword, tresholdsize: dword LOCAL dcb: DCB LOCAL SerialTimeOuts: COMMTIMEOUTS call DWORD ptr pCallBackFunction xor eax, eax mov al, pn mov [com_port+3],al etc. etc. will crash at call DWORD ptr pCallBackFunction always. Since I call SetCallBackPointer first to store a valid address in pCallBackFunction, it should have a valid address. My managed app is written in C# and the relevant part is: public partial class Form1 : Form { public delegate void CallBackDelegate(); public static CallBackDelegate mydelegate; [DllImport("serialport.dll")] private static extern void SetCallBackPointer(CallBackDelegate Delegate); [DllImport("serialport.dll")] public static extern int OpenPort(byte com, uint br, uint inbufsize, uint outbufsize, uint treshsize); public Form1() { InitializeComponent(); mydelegate =new CallBackDelegate(CallbackFunction); SetCallBackPointer(mydelegate); unsafe { int sysstat; int hResult; hResult = OpenPort(Convert.ToByte('5'), 9600, 306, 4, 4); } } public static void CallbackFunction() { MessageBox.Show( "CallBack Function Called by Windows DLL"); } The VS debugger reported that the dll had tried to read/write from/to a protected memory address. But when calling SetCallBackPointer there is no such problem. What am I doing wrong here? Any tips would be great!

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• PHP echo query result in Class??

  - by Jerry

  Hi all I have a question about PHP Class. I am trying to get the result from Mysql via PHP. I would like to know if the best practice is to display the result inside the Class or store the result and handle it in html. For example, display result inside the Class class Schedule { public $currentWeek; function teamQuery($currentWeek){ $this->currentWeek=$currentWeek; } function getSchedule(){ $connection = mysql_connect(DB_SERVER,DB_USER,DB_PASS); if (!$connection) { die("Database connection failed: " . mysql_error()); } $db_select = mysql_select_db(DB_NAME,$connection); if (!$db_select) { die("Database selection failed: " . mysql_error()); } $scheduleQuery=mysql_query("SELECT guest, home, time, winner, pickEnable FROM $this->currentWeek ORDER BY time", $connection); if (!$scheduleQuery){ die("database has errors: ".mysql_error()); } while($row=mysql_fetch_array($scheduleQuery, MYSQL_NUMS)){ //display the result..ex: echo $row['winner']; } mysql_close($scheduleQuery); //no returns } } Or return the query result as a variable and handle in php class Schedule { public $currentWeek; function teamQuery($currentWeek){ $this->currentWeek=$currentWeek; } function getSchedule(){ $connection = mysql_connect(DB_SERVER,DB_USER,DB_PASS); if (!$connection) { die("Database connection failed: " . mysql_error()); } $db_select = mysql_select_db(DB_NAME,$connection); if (!$db_select) { die("Database selection failed: " . mysql_error()); } $scheduleQuery=mysql_query("SELECT guest, home, time, winner, pickEnable FROM $this->currentWeek ORDER BY time", $connection); if (!$scheduleQuery){ die("database has errors: ".mysql_error()); // create an array } $ret = array(); while($row=mysql_fetch_array($scheduleQuery, MYSQL_NUMS)){ $ret[]=$row; } mysql_close($scheduleQuery); return $ret; // and handle the return value in php } } Two things here: I found that returned variable in php is a little bit complex to play with since it is two dimension array. I am not sure what the best practice is and would like to ask you experts opinions. Every time I create a new method, I have to recreate the $connection variable: see below $connection = mysql_connect(DB_SERVER,DB_USER,DB_PASS); if (!$connection) { die("Database connection failed: " . mysql_error()); } $db_select = mysql_select_db(DB_NAME,$connection); if (!$db_select) { die("Database selection failed: " . mysql_error()); } It seems like redundant to me. Can I only do it once instead of calling it anytime I need a query? I am new to php class. hope you guys can help me. thanks.

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• PHP looping through an array to fetch a value for each key from database (third normal form)

  - by zomboble

  I am building a system, mostly for consolidating learning but will be used in practice. I will try and verbally explain the part of the E-R diagram I am focusing on: Each cadet can have many uniformID's Each Uniform ID is a new entry in table uniform, so cadets (table) may look like: id | name | ... | uniformID 1 | Example | ... | 1,2,3 uniform table: id | notes | cadet 1 | Need new blahh | 1 2 | Some stuff needed | 1 3 | Whatever you like | 1 On second thought, looks like I wont need that third column in the db. I am trying to iterate through each id in uniformID, code: <?php $cadet = $_GET['id']; // set from URL $query = mysql_query("SELECT `uniformID` FROM `cadets` WHERE id = '$cadet' LIMIT 1") or die(mysql_error()); // get uniform needed as string // store it while ($row = mysql_fetch_array($query)) { $uniformArray = $row['uniformID']; } echo $uniformArray . " "; $exploded = explode(",", $uniformArray); // convert into an array // for each key in the array perform a new query foreach ($exploded as $key => $value) { $query(count($exploded)); $query[$key] = mysql_query("SELECT * FROM `uniform` WHERE `id` = '$value'"); } ? As I say, this is mainly for consolidation purposes but I have come up with a error, sql is saying: Fatal error: Function name must be a string in C:\wamp\www\intranet\uniform.php on line 82 line 82 is: $query[$key] = mysql_query("SELECT * FROM `uniform` WHERE `id` = '$value'"); I wasn't sure it would work so I tried it and now i'm stuck! EDIT: Thanks to everyone who has contributed to this! This is now the working code: foreach ($exploded as $key => $value) { //$query(count($exploded)); $query = mysql_query("SELECT * FROM `uniform` WHERE `id` = '$value'"); while ($row = mysql_fetch_array($query)) { echo "<tr> <td>" . $row['id'] . "</td> <td>" . $row['note'] . "</td> </tr>"; } } Added the while and did the iteration by nesting it in the foreach

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• Android , Read in binary data and write it to file

  - by Shpongle

  Hi all , Im trying to read in image file from a server , with the code below . It keeps going into the exception. I know the correct number of bytes are being sent as I print them out when received. Im sending the image file from python like so #open the image file and read it into an object imgfile = open (marked_image, 'rb') obj = imgfile.read() #get the no of bytes in the image and convert it to a string bytes = str(len(obj)) #send the number of bytes self.conn.send( bytes + '\n') if self.conn.sendall(obj) == None: imgfile.flush() imgfile.close() print 'Image Sent' else: print 'Error' Here is the android part , this is where I'm having the problem. Any suggestions on the best way to go about receiving the image and writing it to a file ? //read the number of bytes in the image String noOfBytes = in.readLine(); Toast.makeText(this, noOfBytes, 5).show(); byte bytes [] = new byte [Integer.parseInt(noOfBytes)]; //create a file to store the retrieved image File photo = new File(Environment.getExternalStorageDirectory(), "PostKey.jpg"); DataInputStream dis = new DataInputStream(link.getInputStream()); try{ os =new FileOutputStream(photo); byte buf[]=new byte[1024]; int len; while((len=dis.read(buf))>0) os.write(buf,0,len); Toast.makeText(this, "File recieved", 5).show(); os.close(); dis.close(); }catch(IOException e){ Toast.makeText(this, "An IO Error Occured", 5).show(); } EDIT: I still cant seem to get it working. I have been at it since and the result of all my efforts have either resulted in a file that is not the full size or else the app crashing. I know the file is not corrupt before sending server side. As far as I can tell its definitely sending too as the send all method in python sends all or throws an exception in the event of an error and so far it has never thrown an exception. So the client side is messed up . I have to send the file from the server so I cant use the suggestion suggested by Brian .

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• How to replace invalid characters in XML using Javascript or PhP

  - by Raind

  Hi, Need help here for the following: Running PhP, javascript, MySQL, XML. 1) Retrieving file from MySQL and stored it onto XML file. 2) Use javascript function to load XML file (that stored those data). 3) It produces invalid characters in XML file. STEP 1 : Sample of the code in PhP - Loading MySQL DB to store data onto XML file $file= fopen("MapDeals2.xml", "w"); $_xml ="\n"; $_xml .="\n"; while($row1_ThisWeek = mysql_fetch_array($result1_ThisWeek)) { $rRName = $row1_ThisWeek['Retailer_Name']; $rRAddress = $row1_ThisWeek['Retailer_Address1']; $rRAddressPostCode = $row1_ThisWeek['Retailer_AddressPostCode1']; } $_xml .= "<DEAL>\n"; $_xml .= "<DealDescription>" . $d_Description . "</DealDescription>\n"; $_xml .= "<DealURL>" . $d_URL . "</DealURL>\n"; $_xml .= "<DealRName>" . $rRName . "</DealRName>\n"; $_xml .= "<DealRAddress>" . $rRAddress . "</DealRAddress>\n"; $_xml .= "<DealRPostCode>" . $rRAddressPostCode . "</DealRPostCode>\n"; $_xml .= "</DEAL>\n"; } } $_xml .="\n"; fwrite($file, $_xml); fclose($file); STEP 2 : Sample of the code in Javscript - Loading XML file xhttp.open("GET","Test2.xml", false); xhttp.send(""); xmlDoc=xhttp.responseXML; var x=xmlDoc.getElementsByTagName("Employee"); parser = new DOMParser(); xmlDoc = parser.parseFromString("MapDeals2.xml", "text/xml"); for (i=0;i"; . . . } Is there a solution for the above? Looking forward to hear from you soon. Cheers

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• Improved way to build nested array of unique values in javascript

  - by dualmon

  The setup: I have a nested html table structure that displays hierarchical data, and the individual rows can be hidden or shown by the user. Each row has a dom id that is comprised of the level number plus the primary key for the record type on that level. I have to have both, because each level is from a different database table, so the primary key alone is not unique in the dom. example: id="level-1-row-216" I am storing the levels and rows of the visible elements in a cookie, so that when the page reloads the same rows the user had open are can be shown automatically. I don't store the full map of dom ids, because I'm concerned about it getting too verbose, and I want to keep my cookie under 4Kb. So I convert the dom ids to a compact json object like this, with one property for each level, and a unique array of primary keys under each level: { 1:[231,432,7656], 2:[234,121], 3:[234,2], 4:[222,423], 5:[222] } With this structure stored in a cookie, I feed it to my show function and restore the user's previous disclosure state when the page loads. The area for improvement: I'm looking for better option for reducing my map of id selectors down to this compact format. Here is my function: function getVisibleIds(){ // example dom id: level-1-row-216-sub var ids = $("tr#[id^=level]:visible").map(function() { return this.id; }); var levels = {}; for(var i in ids ) { var id = ids[i]; if (typeof id == 'string'){ if (id.match(/^level/)){ // here we extract the number for level and row var level = id.replace(/.*(level-)(\d*)(.*)/, '$2'); var row = id.replace(/.*(row-)(\d*)(.*)/, '$2'); // *** Improvement here? *** // This works, but it seems klugy. In PHP it's one line (see below): if(levels.hasOwnProperty(level)){ if($.inArray(parseInt(row, 10) ,levels[level]) == -1){ levels[level].push(parseInt(row, 10)); } } else { levels[level] = [parseInt(row, 10)]; } } } } return levels; } If I were doing it in PHP, I'd build the compact array like this, but I can't figure it out in javascript: foreach($ids as $id) { if (/* the criteria */){ $level = /* extract it from $id */; $row = /* extract it from $id */; $levels[$level][$row]; } }

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• SQL query - choosing 'last updated' record in a group, better db design?

  - by Jimmy

  Hi, Let's say I have a MySQL database with 3 tables: table 1: Persons, with 1 column ID (int) table 2: Newsletters, with 1 column ID (int) table 3: Subscriptions, with columns Person_ID (int), Newsletter_ID (int), Subscribed (bool), Updated (Datetime) Subscriptions.Person_ID points to a Person, and Subscription.Newsletter_ID points to a Newsletter. Thus, each person may have 0 or more subscriptions to 0 or more magazines at once. The table Subscriptions will also store the entire history of each person's subscriptions to each newsletter. If a particular Person_ID-Newsletter_ID pair doesn't have a row in the Subscriptions table, then it's equivalent to that pair having a subscription status of 'false'. Here is a sample dataset Persons ID 1 2 3 Newsletters ID 4 5 6 Subscriptions Person_ID Newsletter_ID Subscribed Updated 2 4 true 2010-05-01 3 4 true 2010-05-01 3 5 true 2010-05-10 3 4 false 2010-05-15 Thus, as of 2010-05-16, Person 1 has no subscription, Person 2 has a subscription to Newsletter 4, and Person 3 has a subscription to Newsletter 5. Person 3 had a subscription to Newsletter 4 for a while, but not anymore. I'm trying to do 2 kinds of query. A query that shows everyone's active subscriptions as of query time (we can assume that updated will never be in the future -- thus, this means returning the record with the latest 'updated' value for each Person_ID-Newsletter_ID pair, as long as Subscribed is true (if the latest record for a Person_ID-Newsletter_ID pair has a Subscribed status of false, then I don't want that record returned)). A query that returns all active subscriptions for a specific newsletter - same qualification as in 1. regarding records with 'false' in the Subscribed column. I don't use SQL/databases often enough to tell if this design is good, or if the SQL queries needed would be slow on a database with, say, 1M records in the Subscriptions table. I was using the Visual query builder tool in Visual Studio 2010 but I can't even get the query to return the latest updated record for each Person_ID-Newsletter_ID pair. Is it possible to come up with SQL queries that don't involve using subqueries (presumably because they would become too slow with a larger data set)? If not, would it be a better design to have a separate Subscriptions_History table, and every time a subscription status for a Person_ID-Newsletter-ID pair is added to Subscriptions, any existing record for that pair is moved to Subscriptions_History (that way the Subscriptions table only ever contains the latest status update for any Person_ID-Newsletter_ID pair)? I'm using .net on Windows, so would it be easier (or the same, or harder) to do this kind of queries using Linq? Entity Framework? Thanks!

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