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  • Shortest Distance From An Array

    - by notyou61
    I have an ajax function which returns the latitudes and longitudes of locations stored in a database. These are returned and placed in an array. A calculation is performed to return their distance from the users current location based on the latitude/longitude. I would like to return only the record with the shortest calculated distance. My code is as follows: Ajax Success // Success success: function (data) { // Obtain Log/Lat navigator.geolocation.getCurrentPosition(function(position) { // Obtain Current Position Lat/Lon glbVar.latitude = position.coords.latitude; glbVar.longitude = position.coords.longitude; // Console Log //console.log('Lat: ' + glbVar.latitude + ' Lon: ' + glbVar.longitude); // Obtain Location Distances for ( var i = 0; i < data.length; i++ ) { // Location Instances var varLocation = data[i]; // Location Distance varLocation.distance = calculateDistance(glbVar.longitude, glbVar.latitude, varLocation.locationLongitude, varLocation.locationLatitude); } // Sort Locations By Distance var sortedData = data.sort(function(a, b) { // Return Locations return a.distance - b.distance; }); // Output Results $.map(sortedData, function(item) { // Obtain Location Distance varLocationsDistance = calculateDistance(glbVar.longitude, glbVar.latitude, item.locationLongitude, item.locationLatitude); // Obtain Location Radius Assignment if (varLocationsDistance <= varLocationRadius) { // Function Return functionReturn = $({locationID : item.locationID + ', Distance : ' + varLocationsDistance + ' m'}); // Return // Function to get the Min value in Array Array.min = function( sortedData ){ functionReturn = Math.min.apply( Math, sortedData ); // console.log(functionReturn); }; } }); }); } The calculateDistance function returns the distance from the users current location and those from the database. The varLocationsDistance <= varLocationRadius "If" statement returns records within a certain distance radius (100 meters), within that statement I would like to return the shortest distance. I am a self taught amateur web developer and as a result may not have provide enough information for an answer, please let me know. Thanks,

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  • How do I compare two PropertyInfos or methods reliably?

    - by Rob Ashton
    Same for methods too: I am given two instances of PropertyInfo or methods which have been extracted from the class they sit on via GetProperty or GetMember etc, (or from a MemberExpression maybe). I want to determine if they are in fact referring to the same Property or the same Method so (propertyOne == propertyTwo) or (methodOne == methodTwo) Clearly that isn't going to actually work, you might be looking at the same property, but it might have been extracted from different levels of the class hierarchy (in which case generally, propertyOne != propertyTwo) Of course, I could look at DeclaringType, and re-request the property, but this starts getting a bit confusing when you start thinking about Properties/Methods declared on interfaces and implemented on classes Properties/Methods declared on a base class (virtually) and overridden on derived classes Properties/Methods declared on a base class, overridden with 'new' (in IL world this is nothing special iirc) At the end of the day, I just want to be able to do an intelligent equality check between two properties or two methods, I'm 80% sure that the above bullet points don't cover all of the edge cases, and while I could just sit down, write a bunch of tests and start playing about, I'm well aware that my low level knowledge of how these concepts are actually implemented is not excellent, and I'm hoping this is an already answered topic and I just suck at searching. The best answer would give me a couple of methods that achieve the above, explaining what edge cases have been taken care of and why :-)

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  • How do you update a secondary view?

    - by Troy Sartain
    Perhaps there's a better way to set this up so I'm open to suggestions. But here's what I'm doing. I have a main UIView. On top of that I have a UIImageView and another UIView. When the UIImageView changes, I want to change the second UIView. So I have a class for it and the IB object's type is set to the class. In the .m of that class is a drawRect method that draws some rectangles. Also in the .m is a NSMutableArray property that is synthesized. I created an instance of that class in the controller of the main view. The problem: despite the fact that the drawRect works fine when the app starts (as traced in the debugger,) when the UIImageView changes I call a "setNeedsDisplay" on the instance variable of the second view after updating the @synthesize'd array but the drawRect does not get called. I think it has to do with instances. I wouldn't think threading would be an issue here. I just want to draw in a separate area of the screen based on an image also displayed.

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  • How do I force MyEclipse to hot-deploy a JavaScript file to my JBoss instance?

    - by Mike Cialowicz
    I'm having trouble with MyEclipse 7.1.1 hot-deployment of files to my JBoss 4 server. The problem is this: while my server is running, I can make changes to various JAVA and HTML files, which are then hot-deployed immediately (I can see the changes reflected in my browser when I refresh the page). However, while working on a particular JavaScript file, my changes are not being hot-deployed. This makes it very difficult to work on and debug this file, since I have to stop my server, redeploy, and start it again each time I make changes. This is a new problem - it didn't used to happen with this file, so I think something got screwed up in my MyEclipse configuration. I've verified that my projects (JBoss 4 instances) are all set up in "Exploded" mode for hot-deployment. I'm also 99% sure that this isn't an issue with my browser, since I always refresh with CTRL+F5, and I've tried a number of things like clearing my browser cache to get the currently deployed version of the file. I've also tried doing a "clean" on the project while the server is running, and that didn't force a deployment either. Any sort of solution would be helpful. I'd love for MyEclipse to deploy the file automatically, but I'm also open to manually forcing hot-deployment of this particular file while I work on it. Thank you.

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  • How to run stored procedures and ad-hoc scripts asynchronously with "loosely" connected SQL Server 2

    - by sanga
    Is there a way to initiate a script against an instance of SQL server when it is not connected then have it run on the instance the next time it connects? This needs to happen without any intervention from me. Background situation if you are interested: We have about 120 machines each with their own instance of SQL Server 2000. Most of them are laptops. We have merge replication set up with each one. From time to time, there is a need to delete "rogue" guids from some tables in some instances that overwrite legitimate records on the main publisher as well as perform administrative tasks via stored procedure or adhoc sql statements. The problem is there is no telling when each machine is going to be connected to the network. Some folks turn their machines completely off at the end of the day. Others disconnect their machines and take them on business trips, home for the weekend etc. Did I mention that about 35 of these machines are in utility trucks and "attempt" to sync over a wireless connection. Thanks in advance for any assistance or suggestions. Sanga

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  • Unable to diligently close the excel process running in memory

    - by NewAutoUser
    I have developed a VB.Net code for retrieving data from excel file .I load this data in one form and update it back in excel after making necessary modifications in data. This complete flow works fine but most of the times I have observed that even if I close the form; the already loaded excel process does not get closed properly. I tried all possible ways to close it but could not be able to resolve the issue. Find below code which I am using for connecting to excel and let me know if any other approach I may need to follow to resolve this issue. Note: I do not want to kill the excel process as it will kill other instances of the excel Dim connectionString As String connectionString = "Provider=Microsoft.Jet.OLEDB.4.0; Data Source=" & ExcelFilePath & "; Extended Properties=excel 8.0; Persist Security Info=False" excelSheetConnection = New ADODB.Connection If excelSheetConnection.State = 1 Then excelSheetConnection.Close() excelSheetConnection.Open(connectionString) objRsExcelSheet = New ADODB.Recordset If objRsExcelSheet.State = 1 Then objRsExcelSheet.Close() Try If TestID = "" Then objRsExcelSheet.Open("Select * from [" & ActiveSheet & "$]", excelSheetConnection, 1, 1) Else objRsExcelSheet.Open("Select Test_ID,Test_Description,Expected_Result,Type,UI_Element,Action,Data,Risk from [" & ActiveSheet & "$] WHERE TEST_Id LIKE '" & TestID & ".%'", excelSheetConnection, 1, 1) End If getExcelData = objRsExcelSheet Catch errObj As System.Runtime.InteropServices.COMException MsgBox(errObj.Message, , errObj.Source) Return Nothing End Try excelSheetConnection = Nothing objRsExcelSheet = Nothing

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  • Java File Handling, what did I do wrong?

    - by Urda
    Wrote up a basic file handler for a Java Homework assignment, and when I got the assignment back I had some notes about failing to catch a few instances: Buffer from file could have been null. File was not found File stream wasn't closed Here is the block of code that is used for opening a file: /** * Create a Filestream, Buffer, and a String to store the Buffer. */ FileInputStream fin = null; BufferedReader buffRead = null; String loadedString = null; /** Try to open the file from user input */ try { fin = new FileInputStream(programPath + fileToParse); buffRead = new BufferedReader(new InputStreamReader(fin)); loadedString = buffRead.readLine(); fin.close(); } /** Catch the error if we can't open the file */ catch(IOException e) { System.err.println("CRITICAL: Unable to open text file!"); System.err.println("Exiting!"); System.exit(-1); } The one comment I had from him was that fin.close(); needed to be in a finally block, which I did not have at all. But I thought that the way I have created the try/catch it would have prevented an issue with the file not opening. Let me be clear on a few things: This is not for a current assignment (not trying to get someone to do my own work), I have already created my project and have been graded on it. I did not fully understand my Professor's reasoning myself. Finally, I do not have a lot of Java experience, so I was a little confused why my catch wasn't good enough.

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  • C# Casting system.__comobject to class type

    - by ijrufus
    I have an Excel Add-In that I'm currently trying to set up a unit test framework for. For the unit tests I've followed this guide: http://blogs.msdn.com/b/varsha/archive/2010/08/17/writing-automated-test-cases-for-vsto-application.aspx It seems to work fine, until I want to return a class object from my interface. Specifying the class object as the return type throws a "return argument has an invalid type" exception when calling the method. Changing the return type from the class to an object allows me to call the method and get the object, but now I'm unable to cast it as the class and use it as intended, getting this exception message when I try: > Unable to cast COM object of type 'System.__ComObject' to class type > 'anaplan.Utility.XYCoordinates'. Instances of types that represent COM > components cannot be cast to types that do not represent COM > components; however they can be cast to interfaces as long as the > underlying COM component supports QueryInterface calls for the IID of > the interface. I've retrieved the Type name using VisualBasic.Information.TypeName and it's showing it as the class I expect. Is there any way to get the comobject cast back to the class? Or another way to access the properties it has? Or am I just being a bit stupid here?

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  • Using a single texture image unit with multiple sampler uniforms

    - by bcrist
    I am writing a batching system which tracks currently bound textures in order to avoid unnecessary glBindTexture() calls. I'm not sure if I need to keep track of which textures have already been used by a particular batch so that if a texture is used twice, it will be bound to a different TIU for the second sampler which requires it. Is it acceptable for an OpenGL application to use the same texture image unit for multiple samplers within the same shader stage? What about samplers in different shader stages? For example: Fragment shader: ... uniform sampler2D samp1; uniform sampler2D samp2; void main() { ... } Main program: ... glActiveTexture(GL_TEXTURE0); glBindTexture(GL_TEXTURE_2D, tex_id); glUniform1i(samp1_location, 0); glUniform1i(samp2_location, 0); ... I don't see any reason why this shouldn't work, but what about if the shader program also included a vertex shader like this: Vertex shader: ... uniform sampler2D samp1; void main() { ... } In this case, OpenGL is supposed to treat both instances of samp1 as the same variable, and exposes a single location for them. Therefore, the same texture unit is being used in the vertex and fragment shaders. I have read that using the same texture in two different shader stages counts doubly against GL_MAX_COMBINED_TEXTURE_IMAGE_UNITS but this would seem to contradict that. In a quick test on my hardware (HD 6870), all of the following scenarios worked as expected: 1 TIU used for 2 sampler uniforms in same shader stage 1 TIU used for 1 sampler uniform which is used in 2 shader stages 1 TIU used for 2 sampler uniforms, each occurring in a different stage. However, I don't know if this is behavior that I should expect on all hardware/drivers, or if there are performance implications.

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  • How should I lock the table in this VB6 / Access application?

    - by Brian Hooper
    I'm working on a VB6 application using an Access database. The application writes messages to a log table from time to time. Several instances of the application may be running simultaneously and to distinguish them they each have their own run number. The run number is deduced from the log table thus... Set record_set = New ADODB.Recordset query_string = "SELECT MAX(RUN_NUMBER) + 1 AS NEW_RUN_NUMBER FROM ERROR_LOG" record_set.CursorLocation = adUseClient record_set.Open query_string, database_connection, adOpenStatic, , adCmdText record_set.MoveLast If IsNull(record_set.Fields("NEW_RUN_NUMBER")) Then run_number = 0 Else run_number = record_set.Fields("NEW_RUN_NUMBER") End If command_string = "INSERT INTO ERROR_LOG (RUN_NUMBER, SEVERITY, MESSAGE) " & _ " VALUES (" & Str$(run_number) & ", " & _ " " & Str$(SEVERITY_INFORMATION) & ", " & _ " 'Run Started'); " database_connection.Execute command_string Obviously there is a small gap between the calculation of the run number and the appearance of the new row in the database, and to prevent another instance getting access between the two operations I'd like to lock the table; something along the lines of SET TRANSACTION READ WRITE RESERVING ERROR_LOG FOR PROTECTED WRITE; How should I go about doing this? Would locking the recordset do any good (the row in the record set doesn't match any particular row in the database)?

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  • returning a pointed to an object within a std::vector

    - by memC
    I have a very basic question on returning a reference to an element of a vector . There is a vector vec that stores instances of class Foo. I want to access an element from this vector . ( don't want to use the vector index) . How should I code the method getFoo here? #include<vector> #include<stdio.h> #include<iostream> #include<math.h> using namespace std; class Foo { public: Foo(){}; ~Foo(){}; }; class B { public: vector<Foo> vec; Foo* getFoo(); B(){}; ~B(){}; }; Foo* B::getFoo(){ int i; vec.push_back(Foo()); i = vec.size() - 1; // how to return a pointer to vec[i] ?? return vec.at(i); }; int main(){ B b; b = B(); int i = 0; for (i = 0; i < 5; i ++){ b.getFoo(); } return 0; }

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  • Elegant and 'correct' multiton implementation in Objective C?

    - by submachine
    Would you call this implementation of a multiton in objective-c 'elegant'? I have programmatically 'disallowed' use of alloc and allocWithZone: because the decision to allocate or not allocate memory needs to be done based on a key. I know for sure that I need to work with only two instances, so I'm using 'switch-case' instead of a map. #import "Multiton.h" static Multiton *firstInstance = nil; static Multiton *secondInstance = nil; @implementation Multiton + (Multiton *) sharedInstanceForDirection:(char)direction { return [[self allocWithKey:direction] init]; } + (id) allocWithKey:(char)key { return [self allocWithZone:nil andKey:key]; } + (id)allocWithZone:(NSZone *)zone andKey:(char)key { Multiton **sharedInstance; @synchronized(self) { switch (key) { case KEY_1: sharedInstance = &firstInstance; break; case KEY_2: sharedInstance = &secondInstance; break; default: [NSException raise:NSInvalidArgumentException format:@"Invalid key"]; break; } if (*sharedInstance == nil) *sharedInstance = [super allocWithZone:zone]; } return *sharedInstance; } + (id) allocWithZone:(NSZone *)zone { //Do not allow use of alloc and allocWithZone [NSException raise:NSObjectInaccessibleException format:@"Use allocWithZone:andKey: or allocWithKey:"]; return nil; } - (id) copyWithZone:(NSZone *)zone { return self; } - (id) retain { return self; } - (unsigned) retainCount { return NSUIntegerMax; } - (void) release { return; } - (id) autorelease { return self; } - (id) init { [super init]; return self; } PS: I've not tried out if this works as yet, but its compiling cleanly :)

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  • JavaScript: Replacement for XMLSerializer.seralizeToString()?

    - by NRaf
    I'm developing a website using the Seam framework and the RichFaces AJAX library (these isn't really all that important to the problem at hand - just some background). I seem to have uncovered a bug, however, in RichFaces which, in certain instances, will cause AJAX-based updating to fail in IE8 (see here for more info: http://community.jboss.org/message/585737). The following is the code where the exception is occurring: var anchor = oldnode.parentNode; if(!window.opera && !A4J.AJAX.isWebkitBreakingAmps() && oldnode.outerHTML && !oldnode.tagName.match( /(tbody|thead|tfoot|tr|th|td)/i ) ){ LOG.debug("Replace content of node by outerHTML()"); if (!Sarissa._SARISSA_IS_IE || oldnode.tagName.toLowerCase()!="table") { try { oldnode.innerHTML = ""; } catch(e){ LOG.error("Error to clear node content by innerHTML "+e.message); Sarissa.clearChildNodes(oldnode); } } oldnode.outerHTML = new XMLSerializer().serializeToString(newnode); } The last line (the one with XMLSerializer) is where the exception is occurring in IE. I was wondering if anyone knows of any replacement method / library / etc I could use there (only on IE is fine). Thanks.

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  • Is there any way to make this JavaScript tab completion script more efficient?

    - by Saladin Akara
    This code is to be integrated into an AJAX Chat system to enable a tab auto-completion of user names: var usernames = new Array(); usernames[0] = "Saladin"; usernames[1] = "Jyllaby"; usernames[2] = "CadaverKindler"; usernames[3] = "qbsuperstar03"; var text = "Text and something else q"; // Start of the script to be imported var searchTerm = text.slice(text.lastIndexOf(" ") + 1); var i; for(i = 0; i < usernames.length && usernames[i].substr(0,searchTerm.length) != searchTerm; i++); // End of the script to be imported document.write(usernames[i]); A couple of notes to be made: The array of usernames and the text variable would both be loaded from the chat itself via AJAX (which, unfortunately, I don't know), and the final output will be handled by AJAX as well. Is there a more efficient way to do this? Also, any tips on how to handle multiple instances of the searchTerm being found?

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  • ZF2 - ServiceManager injecting into 84 tables... tedious

    - by Dominic Watson
    I originally made another thread about this a couple of months ago in regards to ZF2 injecting into tables with DI during Beta 1 and figured back then that it wasn't really possible. Now ZF2 has been released as version 2.0.0 and ServiceManager is defaulted to instead of DI I guess I have the same question now I'm refactoring. I've got 84 tables that need the DbAdapter injecting into them and I'm sure there has to be a better way as I'm replicating myself SO much. public function getServiceConfig() { return array( 'factories' => array( 'accountTable' => function ($sm) { $dbAdapter = $sm->get('Zend\Db\Adapter\Adapter'); $table = new Model\DbTable\AccountTable($dbAdapter); return $table; }, 'userTable' => function ($sm) { $dbAdapter = $sm->get('Zend\Db\Adapter\Adapter'); $table = new Model\DbTable\UserTable($dbAdapter); return $table; }, // another 82 tables of the above ) ) } With the EventsManager and ServiceManager I have no idea where I stand in getting my application's instances/resources. Thanks, Dom

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  • Why would one want to use the public constructors on Boolean and similar immutable classes?

    - by Robert J. Walker
    (For the purposes of this question, let us assume that one is intentionally not using auto(un)boxing, either because one is writing pre-Java 1.5 code, or because one feels that autounboxing makes it too easy to create NullPointerExceptions.) Take Boolean, for example. The documentation for the Boolean(boolean) constructor says: Note: It is rarely appropriate to use this constructor. Unless a new instance is required, the static factory valueOf(boolean) is generally a better choice. It is likely to yield significantly better space and time performance. My question is, why would you ever want to get a new instance in the first place? It seems like things would be simpler if constructors like that were private. For example, if they were, you could write this with no danger (even if myBoolean were null): if (myBoolean == Boolean.TRUE) It'd be safe because all true Booleans would be references to Boolean.TRUE and all false Booleans would be references to Boolean.FALSE. But because the constructors are public, someone may have used them, which means that you have to write this instead: if (Boolean.TRUE.equals(myBoolean)) But where it really gets bad is when you want to check two Booleans for equality. Something like this: if (myBooleanA == myBooleanB) ...becomes this: if ( (myBooleanA == null && myBooleanB == null) || (myBooleanA == null && myBooleanA.equals(myBooleanB)) ) I can't think of any reason to have separate instances of these objects which is more compelling than not having to do the nonsense above. What say you?

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  • Java constructor using generic types

    - by user37903
    I'm having a hard time wrapping my head around Java generic types. Here's a simple piece of code that in my mind should work, but I'm obviously doing something wrong. Eclipse reports this error in BreweryList.java: The method initBreweryFromObject() is undefined for the type <T> The idea is to fill a Vector with instances of objects that are a subclass of the Brewery class, so the invocation would be something like: BreweryList breweryList = new BreweryList(BrewerySubClass.class, list); BreweryList.java package com.beerme.test; import java.util.Vector; public class BreweryList<T extends Brewery> extends Vector<T> { public BreweryList(Class<T> c, Object[] j) { super(); for (int i = 0; i < j.length; i++) { T item = c.newInstance(); // initBreweryFromObject() is an instance method // of Brewery, of which <T> is a subclass (right?) c.initBreweryFromObject(); // "The method initBreweryFromObject() is undefined // for the type <T>" } } } Brewery.java package com.beerme.test; public class Brewery { public Brewery() { super(); } protected void breweryMethod() { } } BrewerySubClass.java package com.beerme.test; public class BrewerySubClass extends Brewery { public BrewerySubClass() { super(); } public void androidMethod() { } } I'm sure this is a complete-generics-noob question, but I'm stuck. Thanks for any tips!

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  • Database/Object Mapping

    - by Eric
    Hello everyone, This is a beginner question, but it's been frustrating me... I am using C#, by the way. I'd like to make a few classes, each with their own properties and methods. I would also like to have a database to store certain instances of these classes in case I would ever need to look at them again. So, for example... class Polygon { String name; Double perimiter; int numSides; public Double GetArea() { // ... } } class Circle { String name; Double radius; public void PrintName() { // ... } } Say I've got these classes. I also want a database that has the TABLES "Polygon" and "Circle" with the COLUMNS "name" "perimeter" "radius" etc. And I want an easy way to save a class instance into the database, or pull a class instance out of the database. I have previously been using MS Access for my database stuff, which I don't mind using, but I would prefer if nothing other than .NET need to be installed. I've been researching online a bit, but I wanted to get some opinions on here. I have looked at Linq-to-Sql, but it seems you need Sql-Server. Is this true? If so, I'd really rather not use it because I don't want to have to have it installed everywhere. Anway, I'm just fishing for some ideas/insights/suggestions/etc. so please help me out if you can. Thanks.

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  • Entities used to serialize data have changed. How can the serialized data be upgraded for the new entities?

    - by i8abug
    Hi, I have a bunch of simple entity instances that I have serialized to a file. In the future, I know that the structure of these entities (ie, maybe I will rename Name to Header or something). The thing is, I don't want to lose the data that I have saved in all these old files. What is the proper way to either load the data from the old entities into new entities upgrade the old files so that they can be used with new entities Note: I think I am stuck with binary serialization, not xml serialization. Thanks in advance! Edit: So I have an answer for the case I have described. I can use a dataContractSerializer and do something like [DataMember("bar")] private string foo; and change the name in the code and keep the same name that was used for serialization. But what about the following additional cases: The original entity has new members which can be serialized Some serialized members that were in the original entity are removed Some members have actually changed in function (suppose that the original class had a FirstName and LastName member and it has been refactored to have only a FullName member which combines the two) To handle these, I need some sort of interpreter/translator deserialization class but I have no idea what I should use

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  • How to extend an existing Ruby on Rails CMS to host multiple sites?

    - by Andrew
    I am trying to build a CMS I can use to host multiple sites. I know I'm going to end up reinventing the wheel a million times with this project, so I'm thinking about extending an existing open source Ruby on Rails CMS to meet my needs. One of those needs is to be able to run multiple sites, while using only one code-base. That way, when there's an update I want to make, I can update it in one place, and the change is reflected on all of the sites. I think that this will be able to scale by running multiple instances of the application. I think that I can use the domain/subdomain to determine which data to display. For example, someone goes to subdomain1.mysite.com and the application looks in the database for the content for subdomain1. The problem I see is with most pre-built CMS solutions, they are only designed to host one site, including the one I want to use. So the database is structured to work with one site. However, I had the idea that I could overcome this by "creating a new database" for each site, then specifying which database to connect to based on the domain/subdomain as I mentioned above. I'm thinking of hosting this on Heroku, so I'm wondering what my options for this might be. I'm not very familiar with Amazon S3, or Amazon SimpleDB, but I feel like there's some sort of "cloud database" that would make this solution a lot more realistic, than creating a new MySQL database for each site. What do you think? Am I thinking about this the wrong way? What advice do you have to offer in this area?

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  • Caching vector addition over changing collections

    - by DRMacIver
    I have the following setup: I have a largish number of uuids (currently about 10k but expected to grow unboundedly - they're user IDs) and a function f : id - sparse vector with 32-bit integer values (no need to worry about precision). The function is reasonably expensive (not outrageously so, but probably on the order of a few 100ms for a given id). The dimension of the sparse vectors should be assumed to be infinite, as new dimensions can appear over time, but in practice is unlikely to ever exceed about 20k (and individual results of f are unlikely to have more than a few hundred non-zero values). I want to support the following operations efficiently: add a new ID to the collection invalidate an existing ID retrieve sum f(id) in O(changes since last retrieval) i.e. I want to cache the sum of the vectors in a way that's reasonable to do incrementally. One option would be to support a remove ID operation and treat invalidation as a remove followed by an add. The problem with this is that it requires us to keep track of all the old values of f, which is expensive in space. I potentially need to use many instances of this sort of cached structure, so I would like to avoid that. The likely usage pattern is that new IDs are added at a fairly continuous rate and are frequently invalidated at first. Ids which have been invalidated recently are much more likely to be invalidated again than ones which have remained valid for a long time, but in principle an old Id can still be invalidated. Ideally I don't want to do this in memory (or at least I want a way that lets me save the result to disk efficiently), so an idea which lets me piggyback off an existing DB implementation of some sort would be especially appreciated.

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  • C++: Constructor/destructor unresolved when not inline?

    - by Anamon
    In a plugin-based C++ project, I have a TmpClass that is used to exchange data between the main application and the plugins. Therefore the respective TmpClass.h is included in the abstract plugin interface class that is included by the main application project, and implemented by each plugin. As the plugins work on STL vectors of TmpClass instances, there needs to be a default constructor and destructor for the TmpClass. I had declared these in TmpClass.h: class TmpClass { TmpClass(); ~TmpClass(); } and implemented them in TmpClass.cpp. TmpClass::~TmpClass() {} TmpClass::TmpClass() {} However, when compiling plugins this leads to the linker complaining about two unresolved externals - the default constructor and destructor of TmpClass as required by the std::vector<TmpClass> template instantiation - even though all other functions I declare in TmpClass.h and implement in TmpClass.cpp work. As soon as I remove the (empty) default constructor and destructor from the .cpp file and inline them into the class declaration in the .h file, the plugins compile and work. Why is it that the default constructor and destructor have to be inline for this code to compile? Why does it even maatter? (I'm using MSVC++8).

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  • std::bad_cast from parent to child?

    - by polyglot
    For simplicity, class Parent {} class Child1 : Parent {} class Child2 : Parent {} Elsewhere, I created instances of Child1 and Child2 and store it in same vector under Parent: // . . . in .h file, for example vector<Parent> vector_of_parent; // . . . in one particular method Child1 c1(); Child2 c2(); vector_of_parent.push_back(c1); vector_of_parent.push_back(c2); // . . . Then in another method which has access to vector_of_parent, I tried void doSomething(Parent& some_child) { // wrapped in a try block somehow... Child1& c = dynamic_cast<Child1&> some_child; // do something if the cast is successful } void otherMethod() { doSomething(vector_of_parent.at(0)); // vector_of_parent.at(0) is a Child1 } Why is there a std:bad_cast when I call otherMethod()?

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  • Fastest reliable way for Clojure (Java) and Ruby apps to communicate

    - by jkndrkn
    Hi There, We have cloud-hosted (RackSpace cloud) Ruby and Java apps that will interact as follows: Ruby app sends a request to Java app. Request consists of map structure containing strings, integers, other maps, and lists (analogous to JSON). Java app analyzes data and sends reply to Ruby App. We are interested in evaluating both messaging formats (JSON, Buffer Protocols, Thrift, etc.) as well as message transmission channels/techniques (sockets, message queues, RPC, REST, SOAP, etc.) Our criteria: Short round-trip time. Low round-trip-time standard deviation. (We understand that garbage collection pauses and network usage spikes can affect this value). High availability. Scalability (we may want to have multiple instances of Ruby and Java app exchanging point-to-point messages in the future). Ease of debugging and profiling. Good documentation and community support. Bonus points for Clojure support. What combination of message format and transmission method would you recommend? Why? I've gathered here some materials we have already collected for review: Comparison of various java serialization options Comparison of Thrift and Protocol Buffers (old) Comparison of various data interchange formats Comparison of Thrift and Protocol Buffers Fallacies of Protocol Buffers RPC features Discussion of RPC in the context of AMQP (Message-Queueing) Comparison of RPC and message-passing in distributed systems (pdf) Criticism of RPC from perspective of message-passing fan Overview of Avro from Ruby programmer perspective

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  • How do I reference an instance of a class using its tag?

    - by Matt Winters
    I have several instances of a UIControl class Foo being instantiated, one instance corresponding to each cell in a UITableView. The Class has: BOOL selected; UIImageView *imageView; UIImage *imageOne; UIImage *imageTwo; I've assigned each instance a tag: foo.tag = indexPath.row; I would now like to reference the UIImageView.image for a (or several) specific instance(s) by its tag to switch it to the other image. In my search I've seen things like classes being assigned tags using initWithTag (I assume they're assigning tags)... SomeClass *someClass = [[SomeClass alloc]initWithTag:1 ... [someArray addObject: [[SomeClass alloc]initWithTag:2 ... [someArray addObject: [[SomeClass alloc]initWithTag:3 ... ...but I haven't seen how they are later referenced by that tag. I have seen a reference to getChildByTag which had promise, but I can't find it in the documentation or examples (maybe not iphone). Does anyone know how reference the imageView.image within an instance using its tag? Thanks

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