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  • Modifying reference member from const member function in C++

    - by Philipp
    I am working on const-correctness of my code and just wondered why this code compiles: class X { int x; int& y; public: X(int& _y):y(_y) { } void f(int& newY) const { //x = 3; would not work, that's fine y = newY; //does compile. Why? } }; int main(int argc, char **argv) { int i1=0, i2=0; X myX(i1); myX.f(i2); ... } As far as I understand, f() is changing the object myX, although it says to be const. How can I ensure my compiler complains when I do assign to y? (Visual C++ 2008) Thank a lot!

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  • Python: User-Defined Exception That Proves The Rule

    - by bandana
    Python documentations states: Exceptions should typically be derived from the Exception class, either directly or indirectly. the word 'typically' leaves me in an ambiguous state. consider the code: class good(Exception): pass class bad(object): pass Heaven = good() Hell = bad() >>> raise Heaven Traceback (most recent call last): File "<pyshell#163>", line 1, in <module> raise Heaven good >>> raise Hell Traceback (most recent call last): File "<pyshell#171>", line 1, in <module> raise Hell TypeError: exceptions must be classes or instances, not bad so when reading the python docs, should i change 'typically' with ''? what if i have a class hierarchy that has nothing to do with the Exception class, and i want to 'raise' objects belonging to the hierarchy? i can always raise an exception with an argument: raise Exception, Hell This seems slightly awkward to me What's so special about the Exception class, that only its family members can be raised?

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  • When to pass by value?

    - by Dervin Thunk
    Dear all. I was wondering if there are examples of situations where you would purposefully pass an argument by value in C. Let me rephrase. When do you purposefully use C's pass-by-value for large objects? Or, when do you care that the object argument is fully copied in a local variable? EDIT: Now that I think about it, if you can avoid pointers, then do. Nowadays, "deep" copying is possible for mostly everything in small apps, and shallow copying is more prone to pointer bugs. Maybe.

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  • Programming languages: out of the box legibility and extensibility

    - by sova
    Two excellent results of SOLID development ideology are - Legibility - Extensibility over the life of a project (http://en.m.wikipedia.org/wiki/Solid_(object-oriented_design) Although SOLID is a set of language-agnostic design ideas, some languages inherently support these ideas better than others. Out-of-the-box or after various customizations, in your opinion which language is best-suited to be both easily readable and easy to extend functionality in? Some definitions to pre-empt biases and flamewars: Legibility: amount of thinking done to understand the code proportional to the amount of code: (amount_think-energy / amount_code) is fairly constant and as low as possible in the optimal case. Extensibility: Addition of X amount of functionality requires a change in code or code additions in proportion to X (amount_added_functionality / amount_added_code) is fairly constant and as high as possible in the optimal case. Supporting information and tutorials encouraged. Code snippets welcome.

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  • How to debug Fluent nHibernate

    - by Matt Thrower
    Hi, I'm having some trouble with Fluent nHibernate. I added a column to a table and I thought I'd correctly changed the mappings and the connected data objects to correctly reflect this. However when I tried to run my application again I kept getting this error: System.Data.SqlClient.SqlException: Invalid column name 'Workflow_id'. I really couldn't see what the problem was with the changes I'd made so I reverted back to the original versions of the mapping and data object files from source control and removed the offending column from the database. But I'm still getting the same error. I'd like some advice on how to debug this. The SQL that gets reported on the error is semi-nonsensical: SELECT regions0_.Page_id as Page5_1_, regions0_.Id as Id1_, regions0_.Id as Id27_0_, regions0_.RegionId as RegionId27_0_, regions0_.RegionTemplate_id as RegionTe3_27_0_, regions0_.Workflow_id as Workflow4_27_0_ FROM [Region] regions0_ WHERE regions0_.Page_id=? And it won't execute as valid SQL anyway. Any ideas as to where to go from here?

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  • Database Abstraction & Factory Methods

    - by pws5068
    I'm interested in learning more about design practices in PHP for Database Abstraction & Factory methods. For background, my site is a common-interest social networking community currently in beta mode. Currently, I've started moving my old code for object retrieval to factory methods. However, I do feel like I'm limiting myself by keeping a lot of SQL table names and structure separated in each function/method. Questions: Is there a reason to use PEAR (or similar) if I dont anticipate switching databases? Can PEAR interface with the MySqli prepared statements I currently use? Will it help me separate table names from each method? (If no, what other design patterns might I want to research?) Will it slow down my site once I have a significantly large member base?

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  • Java Archtecture Decision !!

    - by santiagobasulto
    Hi everybody! I'm developing a medium Java app, and i'm facing a small problem due to my lack of expirience. I've a custom DAO, which gets "Article" objects from the DataBase. I've the Article class, and the DAO has a method called getArticle(int id), this method returns an Article. The Article has a Category object, and i'm using lazy loading. So, when i request for an Article Category (Article a = new Article(); a.getCategory();) the Article class gets the Category from the DAO and then returns it. I'm now thinking to cache it, so when i request multiple times to an Article's category, the database is only queried one time. My question is: where should i put that cache? I can put it on the Article class (in the DTO), or i can put it on the DAO class. What do you say? Thanks!

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  • Writing a custom auth system (like the default django auth system), use it to generate tables in DB

    - by dotty
    Hay all, I've been reading up on middleware and how to use it with a context object. I want to write a simple middleware class which i can use on my own applications, it will essentially be a cut down version of the django one. The problem i seem to have is that if i have INSTALLED_APPS = ('django.contrib.my_auth') in the settings file, all is well. I've also added MIDDLEWARE_CLASSES = ('django.contrib.my_auth.middleware.MyAuthMiddleware') in it and everything is fine. My question is, how would i make my middleware automatically generate tables from a models.py module, much like how the django auth does when i run manage.py syncdb? thanks

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  • Building a wiki like data model in rails question.

    - by lillq
    I have a data model in which I would like to have an item that has a description that can be edited. I would like to also keep track of all edits to the item. I am running into issues with my current strategy, which is: class Item < ActiveRecord::Base has_one :current_edit, :class_name => "Edit", :foreign_key => "current_edit_id" has_many :edits end class Edit < ActiveRecord::Base belongs_to :item end Can the Item have multiple associations to the same class like this? I was thinking that I should switch to keeping track of the edit version in the Edit object and then just sorting the has_many relationship base on this version.

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  • c++ / c confusion

    - by mrbuxley
    Im trying to make a small app in c++ that saves midifiles with this library. http://musicnote.sourceforge.net/docs/html/index.html The sample code that is given on the homepage looks like this. #include "MusicNoteLib.h" void main() { MusicNoteLib::Player player; // Create the Player Object player.Play("C D E F G A B"); // Play the Music Notes on the default MIDI output port } This piece of code won't compile in Visual studio 2008, I get many errors like MusicNoteLib.h(22) : error C4430: missing type specifier - int assumed. Note: C++ does not support default-int I don't understand the error or where to start looking... There also was some dll files that can be used instead of this h file. #ifndef __MUSICNOTE_LIB_H__EBEE094C_FF6E_43a1_A6CE_D619564F9C6A__ #define __MUSICNOTE_LIB_H__EBEE094C_FF6E_43a1_A6CE_D619564F9C6A__ /** @file MusicNoteLib.h * \brief Main header file for accessing the MusicNote Library */ /// <Summary> /// This header file can be included directly in your project or through /// MusicNoteLib.h of the MusicNoteDll project. If included directly, this /// will be built directly as a satic library. If included through MusicNoteDll /// this will use dllImports through MUSICNOTELIB_API /// </Summary> #ifndef MUSICNOTELIB_API #define MUSICNOTELIB_API #endif // MUSICNOTELIB_API //#include "Player.h" namespace MusicNoteLib /// Music Programming Library { typedef void (__stdcall *LPFNTRACEPROC)(void* pUserData, const TCHAR* szTraceMsg); typedef void (__stdcall *LPFNERRORPROC)(void* pUserData, long lErrCode, const TCHAR* szErrorMsg, const TCHAR* szToken); extern "C" { MUSICNOTELIB_API typedef void MStringPlayer; MUSICNOTELIB_API void* GetCarnaticMusicNoteReader(); /// <Summary> /// Creates a MusicString Player object. /// </Summary> MUSICNOTELIB_API MStringPlayer* CreateMusicStringPlayer(); /// <Summary> /// Plays Music string notes on the default MIDI Output device with the default Timer Resolution. /// Use PlayMusicStringWithOpts() to use custom values. /// @param szMusicNotes the Music string to be played on the MIDI output device /// @return True if the notes were played successfully, False otherwise /// </Summary> MUSICNOTELIB_API bool PlayMusicString(const TCHAR* szMusicNotes); /// <Summary> /// Same as PlayMusicString() except that this method accepts Callbacks. /// The Trace and Error callbacks will be used during the Parse of the Music Notes. /// @param szMusicNotes the Music string to be played on the MIDI output device /// @param traceCallbackProc the Callback to used to report Trace messages /// @param errorCallbackProc the Callback to used to report Error messages /// @param pUserData any user supplied data that should be sent to the Callback /// @return True if the notes were played successfully, False otherwise /// </Summary> MUSICNOTELIB_API bool PlayMusicStringCB(const TCHAR* szMusicNotes, LPFNTRACEPROC traceCallbackProc, LPFNERRORPROC errorCallbackProc, void* pUserData); /// <Summary> /// Plays Music string notes on the given MIDI Output device using the given Timer Resolution. /// Use PlayMusicString() to use default values. /// @param szMusicNotes the Music notes to be played /// @param nMidiOutPortID the device ID of the MIDI output port to be used for the play /// @param nTimerResMS preferred MIDI timer resolution, in MilliSeconds /// @return True if Play was successful, False otherwise /// </Summary> MUSICNOTELIB_API bool PlayMusicStringWithOpts(const TCHAR* szMusicNotes, int nMidiOutPortID, unsigned int nTimerResMS); /// <Summary> /// Same as PlayMusicStringWithOpts() except that this method accepts Callbacks. /// The Trace and Error callbacks will be used during the Parse of the Music Notes. /// @param szMusicNotes the Music notes to be played /// @param nMidiOutPortID the device ID of the MIDI output port to be used for the play /// @param nTimerResMS preferred MIDI timer resolution, in MilliSeconds /// @param traceCallbackProc the Callback to used to report Trace messages /// @param errorCallbackProc the Callback to used to report Error messages /// @param pUserData any user supplied data that should be sent to the Callback /// @return True if Play was successful, False otherwise /// </Summary> MUSICNOTELIB_API bool PlayMusicStringWithOptsCB(const TCHAR* szMusicNotes, int nMidiOutPortID, unsigned int nTimerResMS, LPFNTRACEPROC traceCallbackProc, LPFNERRORPROC errorCallbackProc, void* pUserData); /// <Summary> /// Save the given MusicString content into a MIDI output file /// @param szMusicNotes Music Notes to be converted to MIDI output /// @param szOutputFilePath path of the MIDI output file /// @return True if the the content was saved successfully, False otherwise /// </Summary> MUSICNOTELIB_API bool SaveAsMidiFile(const TCHAR* szMusicNotes, const char* szOutputFilePath); //MUSICNOTELIB_API typedef void (*ParseErrorProc)(const MusicNoteLib::CParser*, MusicNoteLib::CParser::ErrorEventHandlerArgs* pEvArgs); //MUSICNOTELIB_API typedef void (*ParseTraceProc)(const MusicNoteLib::CParser*, MusicNoteLib::CParser::TraceEventHandlerArgs* pEvArgs); MUSICNOTELIB_API void Parse(const TCHAR* szNotes, LPFNTRACEPROC traceCallbackProc, void* pUserData); } // extern "C" } // namespace MusicNoteLib #endif // __MUSICNOTE_LIB_H__EBEE094C_FF6E_43a1_A6CE_D619564F9C6A__

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  • jQuery/javascript events - prototype event handler

    - by Brian M. Hunt
    The following code doesn't work as I intuitively expect it to: function MyObject(input) { input.change(this._foo); this.X = undefined; } MyObject.prototype._foo = function() { alert("This code is never called"); // but if it did this.X = true; } var test_input = $("input#xyz"); // a random, existing input var m = MyObject(test_input); // attach handler (or try to) test_input.change(); // trigger event alert(m.X); // undefined I'd expect that _foo() would be called (and, if that ever happens, that the this variable in _foo() would be an instantiation of MyObject. Does anyone know why this doesn't work, and of any alternative pattern for passing an object to an event handler? Thank you for reading. Brian

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  • Using IPrinciple.Identity.Name as a key in a dataBase to identify user's rows.

    - by bplus
    I'm writing a small intranet app that uses Windows Authentication and Asp.Net MVC. I need to store various bits of data in a db against each user. As far as I can tell the IPrinciple object does not seem to have something like a unique id. So I was thinking I could just use User.Identity.Name as a unique value to identify rows in my db. Is this a bad idea? Is there an alternative to this approach? Thanks for any help.

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  • Attaching user data to AXObserver

    - by Ben Packard
    I am using an AXObserver to monitor when a window is closed. In the callback, I am just raising an NSNotification. All working well. What is the correct syntax for attaching some user data as refcon? The working call looks like this: err6 = AXObserverAddNotification(observerTable, tableRef, kAXUIElementDestroyedNotification, nil); and the callback specified when I create the observer has the signature: static void cbTableClosed (AXObserverRef observer, AXUIElementRef element, CFStringRef notification, void *refcon) I want to replace refcon with an object of my own, but don't know how to change either line. The obvious objective-c type changes through up warnings.

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  • unsetting application role in classic ASP

    - by user303526
    Hi, I'm trying to unset an application role but have been failing miserably. I was able to get the cookie value after setting (sp_setapprole) the application role. But I haven't been able to use that cookie (type varbinary / byte array) in my query to unset using sp_unsetapprole. If it was any other stored procedure it wouldn't have been a problem. I was able to use Command object and create a parameter which takes data type input of adVarBinary (204) and execute the command line.. but to the Server the query goes as below. exec sp_executesql N'sp_unsetapprole @P1 ',N'@P1 varbinary(36)',0x01000000CD11697F8F0ED3627BC1DAD25FB9CEB3A2EC5B289C658235E510CD9F29230000 Since sp_setapprole and sp_unsetapprole have to be run ad hoc, the sql server is failing to run this line. And I'm finding it hard to append varbinary cookie value to a simple query such as 'sp_unsetapprole ' & varKookie so it runs "directly" on to the server. Any kind of suggestions are welcome. Thanks, Nandagopal

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  • Vba to Access record Insert Issue

    - by raam
    I want to insert Values to access table by using VBA control is there is any simple way to do this. i try this code but it does not work properly if i run this code it give the error 'variable not set' can anyone help me. thanks in advance Private Sub CommandButton1_Click() Dim cn As ADODB.Connection Dim strSql As String Dim lngKt As Long Dim dbConnectStr As String Dim Catalog As Object Dim cnt As ADODB.Connection Dim dbPath As String Dim myRecordset As New ADODB.Recordset Dim SQL As String, SQL2 As String dbPath = "table.accdb" dbConnectStr = "Provider=Microsoft.Jet.OLEDB.4.0;Data Source=" & dbPath & ";" SQL = "INSERT INTO Jun_pre (ProductName,DESCRIPTION,SKU,MT,(mt),MRP,Remark,no_of_units_in_a_case) VALUES (""aa"",""bb"",""test"",""testUnit"",""1"",""2"",,""3"",,""4"");" With cnt .Open dbConnectStr 'some other string was there .Execute (SQL) .Close End With End Sub

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  • Autorelease for CGMutablePathRef?

    - by huggie
    Hi, I am developing for iphone. I want to creating a mutable path via CGPathCreateMutable(), and I want to return it out of the function which creates it. I'm suppose to call a CGPathRelease() when I'm done with it. But since I'm returning it I wish to autorelease it. Since Quartz path is a C code (and doesn't look like an objective C object), is it correct that I cannot call autorelease on it? Edit: For others who stumble upon this question, the below advise is for C functions returning Core foundation objects only. For objective C methods returning Core foundation objects, see http://stackoverflow.com/questions/2901942/ownership-regarding-to-returned-quartz-objects

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  • different explanation

    - by Delirium tremens
    The following code echoes 5, not 10: $global_obj = null; class my_class { var $value; function my_class() { global $global_obj; $global_obj = &$this; } } $a = new my_class; $a->my_value = 5; $global_obj->my_value = 10; echo $a->my_value; "Upon first examination, it would seem that the constructor of my_class stores a reference to itself inside the $global_obj variable. Therefore, one would expect that, when we later change the value of $global_obj-my_value to 10, the corresponding value in $a would change as well. Unfortunately, the new operator does not return a reference, but a copy of the newly created object." Please, give me a different explanation.

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  • ASP.NET Thread Safety in aspx.cs code behind file

    - by Tim Michalski
    I am thinking of adding a DataContext as a member variable to my aspx.cs code-behind class for executing LinqToSql queries. Is this thread safe? I am not sure if a new instance of this code-behind class is created for each HTTP request, or if the instance is shared amongst all request threads? My fear is that I will get 10 simultaneous concurrent http requests that will be using the same database session. public partial class MyPage : System.Web.UI.Page { private DataContext myDB = new DataContext(); protected void MyAction_Click(object sender, EventArgs e) { myDB.DoWork(); } }

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  • Unresponsive UI when using BeginInvoke

    - by Kazoom
    Bckground I have a networked application written in C#. my server program has a UI and several communication threads, that read from tcp sockets and display messages on controller UI. Communication with each client is done through a seprate thread. When i recieve some stream of messages from one client , the thread for that client writes on UI, which is a richtextbox on a Form. I call SetTextHelper(string text) method of the form. which looks like this private delegate void MyTextUpdateHandler(string text); public void SetTextHelper(string text) { BeginInvoke(new MyTextUpdateHandler(SetText), new object[] { text }); } public setText(string text) { richtext.Text= text; } Question - If i use BeginInvoke my UI is entirely unresponsive when i m writing large stream of data to UI - Invoke solves that problem, but i read that for multi threaded environment where many thereads are sharing same resource Invoke can lead to deadlocks I share the common ichtextbox between around 16 threads - What would be a good desing for my situation?

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  • I need to debug my BrowserHelperObject (BHO) (in C++ with Visual Studio 2008) after a internet explo

    - by BHOdevelopper
    Hi, here is the situation, i'm developping a Browser Helper Object (BHO) in C++ with Visual Studio 2008, and i learned that the memory wasn't managed the same way in Debug mode than in Release mode. So when i run my BHO in debug mode, internet explorer 8 works just fine and i got no erros at all, the browser stays alive forever, but as soon as i compile it in release mode, i got no errors, no message, nothing, but after 5 minutes i can see through the task manager that internet explorer instances are just eating memory and then the browser just stop responding every time. Please, I really need some hint on how to get a feedback on what could be the error. I heard that, often it was happening because of memory mismanagement. I need a software that just grab a memory dump or something when iexplorer crashes to help me find the problem. Any help is appreciated, I'll be looking for responses every single days, thank you.

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  • Django dictionary in templates: Grab key from another objects attribute

    - by Jordan Messina
    I have a dictionary called number_devices I'm passing to a template, the dictionary keys are the ids of a list of objects I'm also passing to the template (called implementations). I'm iterating over the list of objects and then trying to use the object.id to get a value out of the dict like so: {% for implementation in implementations %} {{ number_devices.implementation.id }} {% endfor %} Unfortunately number_devices.implementation is evaluated first, then the result.id is evaluated obviously returning and displaying nothing. I can't use parentheses like: {{ number_devices.(implementation.id) }} because I get a parse error. How do I get around this annoyance in Django templates? Thanks for any help!

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  • WxPython multiple grid instances

    - by randomPythonHacker
    Does anybody know how I can get multiple instances of the same grid to display on one frame? Whenever I create more than 1 instance of the same object, the display of the original grid widget completely collapses and I'm left unable to do anything with it. For reference, here's the code: import wx import wx.grid as gridlib class levelGrid(gridlib.Grid): def __init__(self, parent, rows, columns): gridlib.Grid.__init__(self, parent, -1) self.moveTo = None self.CreateGrid(rows, columns) self.SetDefaultColSize(32) self.SetDefaultRowSize(32) self.SetColLabelSize(0) self.SetRowLabelSize(0) self.SetDefaultCellBackgroundColour(wx.BLACK) self.EnableDragGridSize(False) class mainFrame(wx.Frame): def __init__(self, parent, id, title): wx.Frame.__init__(self, parent, id, title, size=(768, 576)) editor = levelGrid(self, 25, 25) panel1 = wx.Panel(editor, -1) #vbox = wx.BoxSizer(wx.VERTICAL) #vbox.Add(editor, 1, wx.EXPAND | wx.ALL, 5) #selector = levelGrid(self, 1, 25) #vbox.Add(selector, 1, wx.EXPAND |wx.BOTTOM, 5) self.Centre() self.Show(True) app = wx.App() mainFrame(None, -1, "SLAE") app.MainLoop()

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  • Creating an enum/class from a Database Table

    - by Mark
    I have a database table that essentially contains different types of things. I'll use animals as an example. I have a table called AnimalTypes: AnimalTypes { ID:int, Name:string } I then populate it with: 1:Dog, 2:Cat, 3:Fish I would like to then have some sort of C# object created that functions similar to this enum be entirely read from the database: enum AnimalTypes { Dog = 1, Cat = 2, Fish = 3 } Is there a way to create an enum/class from a database table as described? I basically want to be able to reference things in the AnimalTypes table using intellisense and AnimalTypes.Dog as an example; I don't actually need an enum, just something that kind of functions like one. Is this possible? Edit: I'm not really that thrilled about generating a DLL as I've seen in other related problems. I feel like this should be possible with reflection.

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  • What would you do if you coded a C++/OO cross-platform framework and realize its laying on your disk

    - by Manuel
    This project started as a development platform because i wanted to be able to write games for mobile devices, but also being able to run and debug the code on my desktop machine too (ie, the EPOC device emulator was so bad): the platforms it currently supports are: Window-desktop WinCE Symbian iPhone The architecture it's quite complete with 16bit 565 video framebuffer, blitters, basic raster ops, software pixel shaders, audio mixer with shaders (dsp fx), basic input, a simple virtual file system... although this thing is at it's first write and so there are places where some refactoring would be needed. Everything has been abstracted away and the guiding principle are: mostly clean code, as if it was a book to just be read object-orientation, without sacrifying performances mobile centric The idea was to open source it, but without being able to manage it, i doubt the software itself would benefit from this move.. Nevertheless, i myself have learned a lot from unmaintained projects. So, thanking you in advance for reading all this... really, what would you do?

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  • Jquery Ajax Returned Array - how to handle in Javascript

    - by user232840
    Hi there, If someone could assist me please. I'm doing a jquery Ajax post, for some reason the Json object isn't working so just returning a php array instead $.post ( "classes/RegisterUser.php", $("#frmRegistration").serialize(), function(data) { alert(data); } ); The data is returned to Javascript 100% as array ( [key]=>value [Name] => SomeOneName [Surname] => SomeOneSurName ) How would i go about getting the value of Surname in Javascript? Thanks for your assistance? Regards

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