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  • Difference between std::result_of and decltype

    - by Luc Touraille
    I have some trouble understanding the need for std::result_of in C++0x. If I understood correctly, result_of is used to obtain the resulting type of invoking a function object with certain types of parameters. For example: template <typename F, typename Arg> typename std::result_of<F(Arg)> invoke(F f, Arg a) { return f(a); } I don't really see the difference with the following code: template <typename F, typename Arg> auto invoke(F f, Arg a) -> decltype(f(a)) //uses the f parameter { return f(a); } or template <typename F, typename Arg> auto invoke(F f, Arg a) -> decltype(F()(a)); //"constructs" an F { return f(a); } The only problem I can see with these two solutions is that we need to either: have an instance of the functor to use it in the expression passed to decltype. know a defined constructor for the functor. Am I right in thinking that the only difference between decltype and result_of is that the first one needs an expression whereas the second does not?

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  • Automatically Persisting a Complex Java Object

    - by VeeArr
    For a project I am working on, I need to persist a number of POJOs to a database. The POJOs class definitions are sometimes highly nested, but they should flatten okay, as the nesting is tree-like and contains no cycles (and the base elements are eventually primitives/Strings). It is preferred that the solution used create one table per data type and that the tables will have one field per primitive member in the POJO. Subclassing and similar problems are not issues for this particular project. Does anybody know of any existing solutions that can: Automatically generate a CREATE TABLE definition from the class definition Automatically generate a query to persist an object to the database, given an instance of the object Automatically generate a query to retrieve an object from the database and return it as a POJO, given a key. Solutions that can do this with minimum modifications/annotions to the class files and minimum external configuration are preferred. Example: Java classes //Class to be persisted class TypeA { String guid; long timestamp; TypeB data1; TypeC data2; } class TypeB { int id; int someData; } class TypeC { int id; int otherData; } Could map to CREATE TABLE TypeA ( guid CHAR(255), timestamp BIGINT, data1_id INT, data1_someData INT, data2_id INt, data2_otherData INT ); Or something similar.

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  • Does BeginReceive() get everything sent by BeginSend()?

    - by IVlad
    I'm writing a program that will have both a server side and a client side, and the client side will connect to a server hosted by the same program (but by another instance of it, and usually on another machine). So basically, I have control over both aspects of the protocol. I am using BeginReceive() and BeginSend() on both sides to send and receive data. My question is if these two statements are true: Using a call to BeginReceive() will give me the entire data that was sent by a single call to BeginSend() on the other end when the callback function is called. Using a call to BeginSend() will send the entire data I pass it to the other end, and it will all be received by a single call to BeginReceive() on the other end. The two are basically the same in fact. If the answer is no, which I'm guessing is the case based on what I've read about sockets, what is the best way to handle commands? I'm writing a game that will have commands such as PUT X Y. I was thinking of appending a special character (# for example) to the end of each command, and each time I receive data, I append it to a buffer, then parse it only after I encounter a #.

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  • Error using maven profiles

    - by user3127896
    I've added two profiles to my application and that how it looks: <profiles> <profile> <id>dev</id> <properties> <db.username>root</db.username> <db.password>root</db.password> <db.connectionURL>localhost:3306</db.connectionURL> <db.driverClass>com.mysql.jdbc.Driver</db.driverClass> </properties> </profile> <profile> <id>prod</id> <properties> <db.username>prodroot</db.username> <db.password>prodpass</db.password> <db.connectionURL>localhost:3306</db.connectionURL> <db.driverClass>com.mysql.jdbc.Driver</db.driverClass> </properties> </profile> </profiles> In my jdbc.properties file i changed values like this: jdbc.driverClassName=${db.driverClass} jdbc.dialect=org.hibernate.dialect.MySQLDialect jdbc.databaseurl=jdbc:mysql://${db.connectionURL}/dbname jdbc.username=${db.username} jdbc.password=${db.password} And here's bean from spring-container.xml <bean id="dataSource" class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close" p:driverClassName="${jdbc.driverClassName}" p:url="${jdbc.databaseurl}" p:username="${jdbc.username}" p:password="${jdbc.password}" /> When i try to deploy my application i got following error: SEVERE: Exception sending context initialized event to listener instance of class org.springframework.web.context.ContextLoaderListener org.springframework.beans.factory.BeanDefinitionStoreException: Invalid bean definition with name 'dataSource' defined in ServletContext resource [/WEB-INF/spring-servlet.xml]: Could not resolve placeholder 'db.driverClass' Structure of project: Any ideas what i'm doing wrong? Thanks in advance!

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  • C++ Instantiate class and add name to array/vector then cycle through update functions from the array

    - by SD42
    I have a bunch of classes in a basic (and badly coded!) game engine that are currently instantiated in the code and have to have their individual update functions called. What I want to do is be able to create an instance of a class, pass the name to an array, and then subsequently cycle through the array to call the update functions of each class. I'm unsure as to whether or not this is an impossible or spectacularly stupid way of trying to manage objects, so please tell me if it is. So currently I might have manually instantiated Enemy class a couple of times: Enemy enem1; Enemy enem2; I then have to update them manually in the game loop: enem1.update(); enem2.update(); What method should I use to be able to spawn and destroy instances of the enemy class during gametime? Is it possible to populate an array with instantiated names and then do something like (and i'm aware this doesn't work); array[x].update(); Then iterate through the names in the array? Anything that even points me in the right direction would be greatly appreciated!

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  • Strange lazy load problem

    - by JooLio
    public class QuickQuoteTemplate { ... public virtual IList<QuickQuoteTemplateItem> InnerItems { get; set; } ... } public class QuickQuoteTemplateItem { ... public virtual IList<QuickQuoteTemplateItem> InnerItems { get; set; } ... } <class name="QuickQuoteTemplate" table="SA_QUICK_QUOTE_TEMPLATE"> ... <bag name="InnerItems" lazy="false" inverse="true" cascade="delete" > <key column="PARENT_QQ_TEMPLATE_ID" ></key> <one-to-many class="QuickQuoteTemplateItem" /> </bag> ... </class> <class name="QuickQuoteTemplateItem" table="SA_QUICK_QUOTE_TEMPLATE_ITEMS"> ... <bag name="InnerItems" lazy="false" inverse="false" cascade="delete"> <key column="PARENT_ITEM_ID" /> <one-to-many class="QuickQuoteTemplateItem" /> </bag> ... </class> InnerItems collections is set as no lazy, but after disposing the ISession instance, quickQuote.InnerItems is crying "failed to lazily initialize a collection, no session or session was closed". I've even tried to call InnerItems before the session is closed by myself. It successfully retrieves, but after disposing of the session it becomes not initialized.

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  • destructor being called by subclass

    - by zero
    I'm currently learning more about php objects and constructors/destructors, but i've noticed in my code that the parent class's destructor is being called twice, I thought it was because i was extending the first class to my second class and that the second class was calling it, but this is what the php docs say about that: Like constructors, parent destructors will not be called implicitly by the engine. In order to run a parent destructor, one would have to explicitly call parent::__destruct() in the destructor body. so if it is not being called by the subclass then is it because by extended the first class that i've made a reference to the parent class making it call itself twice or I'm I way off base here? the code: <?php class test{ public $test1 = "this is a test of a pulic property"; private $test2 = "this is a test of a private property"; protected $test3 = "this is a test of a protected property"; const hello = 900000; function __construct($h){ //echo 'this is the constructor test '.$h; } function x($x2){ echo ' this is fn x'.$x2; } function y(){ print "this is fn y"; } } $obj = new test("this is an \"arg\" sent to instance of test"); class hey extends test{ function hey(){ $this->x('<br>from the host with the most'); echo ' <br>from hey class'.$this->test3; } } $obj2 = new hey(); echo $obj2::hello; ?>

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  • Jquery ajax load not working

    - by Slay
    This is my code: test.html <html> <head> <title>test</title> <script src="http://ajax.googleapis.com/ajax/libs/jquery/1.8.2/jquery.min.js"></script> <script> $(document).ready(function(){ $(window).bind('hashchange', function(){ $('#result').load('test2.html', function(){ alert('Load was performed.'); }); }); }); </script> </head> <body> <a href="#Test1">Test 1</a> <a href="#Test2">Test 2</a> <div id="result"></div> </body> </html> test2.html <h3>This is content from test2.html</h3> I want to detect the specific page to load using window.hash in change. For instance if user go to http://localhost/test.html#test2 The main container(result) in the page will do an ajax load call to test2.html to get the content. I can't manage to get this simple code working. Appreciate if someone can guide me in the right direction. Thanks.

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  • How to increase my "advanced" knowledge of PHP further? (quickly)

    - by Kerry
    I have been working with PHP for years and gotten a very good grasp of the language, created many advanced and not-so-advanced systems that are working very well. The problem I'm running into is that I only learn when I find a need for something that I haven't learned before. This causes me to look up solutions and other code that handles the problem, and so I will learn about a new function or structure that I hadn't seen before. It is in this way that I have learned many of my better techniques (such as studying classes put out by Amazon, Google or other major companies). The main problem with this is the concept of not being able to learn something if you don't know it exists. For instance, it took me several months of programming to learn about the empty() function, and I simply would check the string length using strlen() to check for empty values. I'm now getting into building bigger and bigger systems, and I've started to read blogs like highscalability.com and been researching MySQL replication and server data for scaling. I know that structure of your code is very important to make full systems work. After reading a recent blog about reddit's structure, it made me question if there is some standard or "accepted systems" out there. I have looked into frameworks (I've used Kohana, which I regretted, but decided that PHP frameworks were not for me) and I prefer my own library of functions rather than having a framework. My current structure is a mix between WordPress, Kohana and my own knowledge. The ways I can see as being potentially beneficial are: Read blogs Read tutorials Work with someone else Read a book What would be the best way(s) to "get to the next level" the level of being a very good system developer?

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  • Displaying Query Results Horizontally

    - by AndyD273
    I am wondering if it is possible to take the results of a query and return them as a CSV string instead of as a column of cells. Basically, we have a table called Customers, and we have a table called CustomerTypeLines, and each Customer can have multiple CustomerTypeLines. When I run a query against it, I run into problems when I want to check multiple types, for instance: Select * from Customers a Inner Join CustomerTypeLines b on a.CustomerID = b.CustomerID where b.CustomerTypeID = 14 and b.CustomerTypeID = 66 ...returns nothing because a customer can't have both on the same line, obviously. In order to make it work, I had to add a field to Customers called CustomerTypes that looks like ,14,66,67, so I can do a Where a.CustomerTypes like '%,14,%' and a.CustomerTypes like '%,66,%' which returns 85 rows. Of course this is a pain because I have to make my program rebuild this field for that Customer each time the CustomerTypeLines table is changed. It would be nice if I could do a sub query in my where that would do the work for me, so instead of returning the results like: 14 66 67 it would return them like ,14,66,67, Is this possible?

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  • Doing a global count of an object type (like Users), best practice?

    - by user246114
    Hi, I know keeping global counters is frowned upon in app engine. I am interested in getting some stats though, like once every 24 hours. For example, I'd like to count the number of User objects in the system once every 24 hours. So how do we do this? Do we simply keep a set of admin tool functions which do something like: SELECT FROM com.me.project.server.User; and just see what the size of the returned List is? This is kind of a bummer because the datastore would have to deserialize every single User instance to create the returned list, right? I could optimize this possibly by asking for only the keys to be returned, so the whole User object doesn't have to be deserialized. Then again, a global counter for # of users probably would create too much contention, because there probably won't be hundreds of signups a minute for the service I'm creating. How should we go about doing this? Getting my total number of users once a day is probably a pretty typical operation? Thank you

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  • When to use () with classes?

    - by SoulBeaver
    This is really starting to confuse the hell out of me. When do I use them, when don't I? For example I was reading a .cpp on linked lists whose class declaration was: struct CarPart { long PartNumber; char Partname[40]; double UnitPrice; CarPart *next; }; class ListOfParts { int size; public: CarPart *head; ListOfParts(); ~ListOfParts(); const int count() const; void insert( CarPart *item ); CarPart *retrieve( int pos ); }; With this code, why am I allowed to write ListOfParts *pPart = new ListOfParts(); CarPart *pCarPart = new CarPart; Declaring an instance of ListOfParts requires (), but not my CarPart? That's confusing me. When I asked a question before and people told me that such a declaration is a function that returns a ListOfParts object, but not the actual constructor. So I'm guessing this is still something different. What's happening here? PS: Am I correct to assume that the const to the right of count() means I cannot modify any values in count?

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  • Common block usage in Fortran

    - by Crystal
    I'm new to Fortran and just doing some simple things for work. And as a new programmer in general, not sure exactly how this works, so excuse me if my explanation or notation is not the best. At the top of the .F file there are common declarations. The person explaining it to me said think of it like a struct in C, and that they are global. Also in that same .F file, they have it declared with what type. So it's something like: COMMON SOMEVAR INTEGER*2 SOMEVAR And then when I actually see it being used in some other file, they declare local variables, (e.g. SOMEVAR_LOCAL) and depending on the condition, they set SOMEVAR_LOCAL = 1 or 0. Then there is another conditional later down the line that will say something like IF (SOMEVAR_LOCAL. eq. 1) SOMEVAR(PARAM) = 1; (Again I apologize if this is not proper Fortran, but I don't have access to the code right now). So it seems to me that there is a "struct" like variable called SOMEVAR that is of some length (2 bytes of data?), then there is a local variable that is used as a flag so that later down the line, the global struct SOMEVAR can be set to that value. But because there is (PARAM), it's like an array for that particular instance? Thanks. Sorry for my bad explanation, but hopefully you will understand what I am asking.

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  • Is there an Easier way to Get a 3 deep Panel Control from a Form in order to add a new Control to it programmatically?

    - by Mark Sweetman
    I have a VB Windows Program Created by someone else, it was programmed so that anyone could Add to the functionality of the program through the use of Class Libraries, the Program calls them (ie... the Class Libraries, DLL files) Plugins, The Plugin I am creating is a C# Class Library. ie.. .dll This specific Plugin Im working on Adds a Simple DateTime Clock Function in the form of a Label and inserts it into a Panel that is 3 Deep. The Code I have I have tested and it works. My Question is this: Is there a better way to do it? for instance I use Controls.Find 3 different times, each time I know what Panel I am looking for and there will only be a single Panel added to the Control[] array. So again Im doing a foreach on an array that only holds a single element 3 different times. Now like I said the code works and does as I expected it to. It just seems overly redudant, and Im wondering if there could be a performance issue. here is the code: foreach (Control p0 in mDesigner.Controls) if (p0.Name == "Panel1") { Control panel1 = (Control)p0; Control[] controls = panel1.Controls.Find("Panel2", true); foreach (Control p1 in controls) if (p1.Name == "Panel2") { Control panel2 = (Control)p1; Control[] controls1 = panel2.Controls.Find("Panel3", true); foreach(Control p2 in controls1) if (p2.Name == "Panel3") { Control panel3 = (Control)p2; panel3.Controls.Add(clock); } } }

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  • what happens when you stop VS debugger?

    - by mare
    If I have a line like this ContentRepository.Update(existing); that goes into datastore repository to update some object and I have a try..catch block in this Update function like this: string file = XmlProvider.DataStorePhysicalPath + o.GetType().Name + Path.DirectorySeparatorChar + o.Slug + ".xml"; DataContractSerializer dcs = new DataContractSerializer(typeof (BaseContentObject)); using ( XmlDictionaryWriter myWriter = XmlDictionaryWriter.CreateTextWriter(new FileStream(file, FileMode.Truncate, FileAccess.Write), Encoding.UTF8)) { try { dcs.WriteObject(myWriter, o); myWriter.Close(); } catch (Exception) { // if anything goes wrong, delete the created file if (File.Exists(file)) File.Delete(file); if(myWriter.WriteState!=WriteState.Closed) myWriter.Close(); } } then why would Visual Studio go on with calling Update() if I click "Stop" in debugging session on the above line? For instance, I came to that line by going line by line pressing F10 and now I'm on that line which is colored yellow and I press Stop. Apparently what happens is, VS goes to execute the Update() method and somehow figures out something gone wrong and goes into "catch" and deletes the file, which is wrong, because I want my catch to work when there is a true exception not when I debug a program and force to stop it.

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  • Save many-to-one relationship from JSON into Core Data

    - by Snow Crash
    I'm wanting to save a Many-to-one relationship parsed from JSON into Core Data. The code that parses the JSON and does the insert into Core Data looks like this: for (NSDictionary *thisRecipe in recipes) { Recipe *recipe = [NSEntityDescription insertNewObjectForEntityForName:@"Recipe" inManagedObjectContext:insertionContext]; recipe.title = [thisRecipe objectForKey:@"Title"]; NSDictionary *ingredientsForRecipe = [thisRecipe objectForKey:@"Ingredients"]; NSArray *ingredientsArray = [ingredientsForRecipe objectForKey:@"Results"]; for (NSDictionary *thisIngredient in ingredientsArray) { Ingredient *ingredient = [NSEntityDescription insertNewObjectForEntityForName:@"Ingredient" inManagedObjectContext:insertionContext]; ingredient.name = [thisIngredient objectForKey:@"Name"]; } } NSSet *ingredientsSet = [NSSet ingredientsArray]; [recipe setIngredients:ingredientsSet]; Notes: "setIngredients" is a Core Data generated accessor method. There is a many-to-one relationship between Ingredients and Recipe However, when I run this I get the following error: NSCFDictionary managedObjectContext]: unrecognized selector sent to instance If I remove the last line (i.e. [recipe setIngredients:ingredientsSet];) then, taking a peek at the SQLite database, I see the Recipe and Ingredients have been stored but no relationship has been created between Recipe and Ingredients Any suggestions as to how to ensure the relationship is stored correctly?

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  • C++: getting the address of the start of an std::vector ?

    - by shoosh
    Sometimes it is useful to use the starting address of an std::vector and temporarily treat that address as the address of a regularly allocated buffer. For instance replace this: char* buf = new char[size]; fillTheBuffer(buf, size); useTheBuffer(buf, size); delete[] buf; With This: vector<char> buf(size); fillTheBuffer(&buf[0], size); useTheBuffer(&buf[0], size); The advantage of this is of course that the buffer is deallocated automatically and I don't have to worry about the delete[]. The problem I'm having with this is when size == 0. In that case the first version works ok. An empty buffer is "allocated" and the subsequent functions do nothing size they get size == 0. The second version however fails if size == 0 since calling buf[0] may rightly contain an assertion that 0 < size. So is there an alternative to the idiom &buf[0] that returns the address of the start of the vector even if the vector is empty? I've also considered using buf.begin() but according to the standard it isn't even guaranteed to return a pointer.

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  • Multiple locking task (threading)

    - by Archeg
    I need to implement the class that should perform locking mechanism in our framework. We have several threads and they are numbered 0,1,2,3.... We have a static class called ResourceHandler, that should lock these threads on given objects. The requirement is that n Lock() invokes should be realeased by m Release() invokes, where n = [0..] and m = [0..]. So no matter how many locks was performed on single object, only one Release call is enough to unlock all. Even further if o object is not locked, Release call should perform nothing. Also we need to know what objects are locked on what threads. I have this implementation: public class ResourceHandler { private readonly Dictionary<int, List<object>> _locks = new Dictionary<int, List<object>>(); public static ResourceHandler Instance {/* Singleton */} public virtual void Lock(int threadNumber, object obj) { Monitor.Enter(obj); if (!_locks.ContainsKey(threadNumber)) {_locks.Add(new List<object>());} _locks[threadNumber].Add(obj); } public virtual void Release(int threadNumber, object obj) { // Check whether we have threadN in _lock and skip if not var count = _locks[threadNumber].Count(x => x == obj); _locks[threadNumber].RemoveAll(x => x == obj); for (int i=0; i<count; i++) { Monitor.Exit(obj); } } // ..... } Actually what I am worried here about is thread-safety. I'm actually not sure, is it thread-safe or not, and it's a real pain to fix that. Am I doing the task correctly and how can I ensure that this is thread-safe?

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  • The cross-thread usage of "HttpContext.Current" property and related things

    - by smwikipedia
    I read from < Essential ASP.NET with Examples in C# the following statement: Another useful property to know about is the static Current property of the HttpContext class. This property always points to the current instance of the HttpContext class for the request being serviced. This can be convenient if you are writing helper classes that will be used from pages or other pipeline classes and may need to access the context for whatever reason. By using the static Current property to retrieve the context, you can avoid passing a reference to it to helper classes. For example, the class shown in Listing 4-1 uses the Current property of the context to access the QueryString and print something to the current response buffer. Note that for this static property to be correctly initialized, the caller must be executing on the original request thread, so if you have spawned additional threads to perform work during a request, you must take care to provide access to the context class yourself. I am wondering about the root cause of the bold part, and one thing leads to another, here is my thoughts: We know that a process can have multiple threads. Each of these threads have their own stacks, respectively. These threads also have access to a shared memory area, the heap. The stack then, as I understand it, is kind of where all the context for that thread is stored. For a thread to access something in the heap it must use a pointer, and the pointer is stored on its stack. So when we make some cross-thread calls, we must make sure that all the necessary context info is passed from the caller thread's stack to the callee thread's stack. But I am not quite sure if I made any mistake. Any comments will be deeply appreciated. Thanks. ADD Here the stack is limited to user stack.

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  • Generic factory of generic containers

    - by Feuermurmel
    I have a generic abstract class Factory<T> with a method createBoxedInstance() which returns instances of T created by implementations of createInstance() wrapped in the generic container Box<T>. abstract class Factory<T> { abstract T createInstance(); public final Box<T> createBoxedInstance() { return new Box<T>(createInstance()); } public final class Box<T> { public final T content; public Box(T content) { this.content = content; } } } At some points I need a container of type Box<S> where S is an ancestor of T. Is it possible to make createBoxedInstance() itself generic so that it will return instances of Box<S> where S is chosen by the caller? Sadly, defining the function as follows does not work as a type parameter cannot be declared using the super keyword, only used. public final <S super T> Box<S> createBoxedInstance() { return new Box<S>(createInstance()); } The only alternative I see, is to make all places that need an instance of Box<S> accept Box<? extends S> which makes the container's content member assignable to S. Is there some way around this without re-boxing the instances of T into containers of type Box<S>? (I know I could just cast the Box<T> to a Box<S> but I would feel very, very guilty.)

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  • self-destructing objects in php5?

    - by user151841
    I am working on a class in php that is basically an interface to a database row. I wanted to create a delete() method that would 1. delete the database row and 2. destroy the instance of itself so that further attempts to manipulate the row via the object would throw warnings. Doing some googling, it seems that, in php5, it's not possible for an object to unset itself. http://bugs.php.net/bug.php?id=36971 In fact they discuss the very situation I was wanting to do :( So how should I proceed? I could make boolean flag as a class property, for whether the row still exists, and have each operation check that flag and throw an error if the row has been deleted. This maintains the oo structure of code, so I would have $objDbRow->delete(); But then I have to put checks at the beginning of each method. Or, I could implement a __destruct method that deletes the row. But that would seem counter-intuitive to me; if I saw in code unset($objDbRow); All I would suspect that's happening is that the object is being discarded, not that a row is being deleted. So that to me would seem like bad practice.

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  • Multiple PictureBoxs' C#

    - by Austin Smith
    I'm having a hard time figuring this out. I know pictureBox only lets you display one image a time. I'm trying to create a pictureBox for each image in my collection. For instance if I have ten images in my List, then the method should create ten pictureBox for those respective images so each one is displayes in a pictureBox. I'm not sure which would be better a for loop or a foreach loop instead. every time the loop increments both the varaiables XCoordinate and YCoordinate which are the location of the PictireBox shoulld increase so that the PictureBox won't overlap one another in the Form. The reason for the method is that the number of images in the collection can change everytime the application will run. That's why I'm not creating them manually. So after its done all the pictures in the list should appear in a picture.Box. The box should be all the same size the only difference is the location on the form and the images inside them. Please any help and I will be grateful

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  • implementing user tracking (logging) in Rails 3

    - by seth.vargo
    Hi, I'm creating a Rails application in which logging individual user actions is vital. Every time a user clicks a url, I want to log the action along with all parameters. Here is my current implementation: class CreateActivityLogs < ActiveRecord::Migration create_table :activity_logs do |t| t.references :user t.string :ip_address t.string :referring_url t.string :current_url t.text :params t.text :action t.timestamps end end   class ActivityLog < ActiveRecord::Base belongs_to :user end In a controller, I'd like to be able to do something like the following: ... ActivityLog::log @user.id, params, 'did foo with bar' ... I'd like to have the ActivityLog::log method automatically get the IP address, referring url, and current url (I know how to do this already) and create a new record in the table. So, my questions are: How do I do this? How do I use ActivityLog without having to create an instance everytime I want to log? Is this the best way? Some people have argued for a flat-file log for this kind of logging - however, I want admins to be able to see a user's activity in the backend as well, so I thought a database solution may be better?

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  • Can't call an object method. PHP reports variable undefined

    - by user1285697
    This is the weirdest bug! It is probably something silly, but I have no idea how to fix it. If anyone could help, I would be most grateful! I have three files, one is called items.php, another is called tableFunctions.php, and the third is called mysql.php. I use two global objects called 'mysql' and 'tableFunctions'. They are stored in the files 'mysql.php', and 'tableFunctions.php', respectively. In each file, I create an instance of its object, assigning it to the global variable $_mysql, or $_table. like this: In the file mysql.php: global $_mysql; $_mysql = new mysql(); In the file tableFunctions.php: global $_table; $_table = new tableFunctions(); Here's how it is supposed to work: The items.php file includes the tableFunctions.php file... Which in turn, needs the mysql.php file, so it includes it too. In the items.php file, I call the method getTable(), which is contained in the object tableFunctions.(and in the variable $_table.) Like this: $t = $_table->getTable('items'); The getTable function calls the method, arrayFromResult(), which is contained within in the object mysql.(and in the variable $_mysql.) Like this: $result = $_mysql->arrayFromResult($r); That's where I get the error. PHP says that the variable '$_mysql' is undefined, but I defined it in the 'mysql.php' file.(see above) I also included mysql.php with the following code: include_once 'mysql.php'; I have no idea what is wrong! If anyone can help that would be much appreciated. The source files can be downloaded with the following link: https://www.dropbox.com/sh/bjj2gyjsybym89r/YLxqyNvQdn

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  • Why can't I overwrite the prototype of `Array` (`Array.prototype`)?

    - by user828896
    I set the prototype of Array as an instance of my, I think book.aa will display "aa", but it displays "undefined", why? Thanks! <html> <head> <title>Array Properties</title> <h2>Array Properties</h2> <script type="text/javascript"> function my() { this.aa = 'aa'; } Array.prototype = new my(); Array.prototype.bb = "bb"; var book = new Array(); book[0] = "War and Peace"; </script> </head> <body bgcolor="lightblue"> <script type="text/javascript"> document.write(book.aa+book.bb); </script> </body> </html>

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