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  • Why in Objective-C, we use self = [super init] instead of just [super init]?

    - by ????
    In a book, I saw that if a subclass is overriding a superclass's method, we may have self = [super init]; First, is this supposed to be done in the subclass's init method? Second, I wonder why the call is not just [super init]; ? I mean, at the time of calling init, the memory is allocated by alloc already (I think by [Foobar alloc] where Foobar is the subclass's name. So can't we just call [super init] to initialize the member variables? Why do we have to get the return value of init and assign to self? I mean, before calling [super init], self should be pointing to a valid memory allocation chuck... so why assigning something to self again? (if assigning, won't [super init] just return self's existing value?)

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  • How do I dynamically define an instance variable?

    - by Moses
    Hi everyone, I have two classes (class1 and class2) that just store data, no methods. I have a third class that has an instance variable that, depending on some user input, will be set to one of the two classes. So, in the third class I declare the variable generically as NSObject *aClass; and during runtime set it to whatever it should be. aClass = [[Class1 alloc] init]; // or aClass = [[Class2 alloc] init]; However, when I try to access fields from aClass NSString *str = aClass.field1; It gives me the error: request for member 'field1' in something not a structure or a union. Field1 is declared in both class1 and class2. When I try to cast aClass aClass = (Class1 *) aClass; it gives the same error. What am I doing wrong, is there a better way to do this?

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  • How to insert value to Magento database using module

    - by Kasmin Nicko
    I want to insert value to the database I created. The value would be insert to post column. I have code like this in the IndexController.php class My_Module_IndexController extends Mage_Core_Controller_Front_Action { public function postAction() { $post = Mage::getModel('my/model'); $post->setPost('My Post Here'); $post->save(); } } But after I ran this script, I got the following error Fatal error: Call to a member function setPost() on a non-object in C:\xampp\htdocs\magento\app\code\community\My\Module\controllers\IndexController.php on line 7 What is something I miss?

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  • What is a great resource for learning about the implementation details of .NET generic collections?

    - by Jimmy W
    Hi all, I'm interested in understanding the underlying implementation details of generic collections in .NET. What I have in mind are details such as how the collections are stored, how each member of a collection is accessed by the CLR, etc. For collections that are analogous to traditional data structures, such as LinkedList and Dictionary, I think I have an understanding of what's going on underneath. However, I'm not as certain about collections like List (how is set up such that it is both indexable and expandable?) and SortedList, so any leads as to what I could look up to learn more about them would be greatly appreciated.

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  • Claims-based Authentication: Are strings the essence of claims?

    - by Rising Star
    I've been programming with claims-based authentication for some time now with Windows Identity Foundation. It appears to me that in Windows Identity Foundation, once a user is logged in, the claims are basically strings of information that describe the user. With the old role-based authentication, I could say that a user is or is not a member of a given group, but with claims-based authentication, I can now have strings of information that describe a user. "This user is female". This user was born on "July 6, 1975". "This user logged in using a USB key". Is it the essence of claims-based authentication,that I have strings of information about the user given to the application by the framework?

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  • Hot to log in to a website using installed twill?

    - by brilliant
    Hello, everybody!!!! I have just successfully installed TWILL on my computer with the help of one very supportive member of "StackOverflow" (you can check it out HERE) and have tried to run one of the simple examples on the twill documentation page (you can see that page HERE). Here is that example: Let's say my username on www.slash.org is lynxye and my password is mammal. When I try to enter that exanple code into my Python prompt, I can only enter the first line of the code bexcause when I click on "Enter" to start a new line, I get some error messages right away: The same happens when I try to enter this code into my terminal: I think I miss out on some basics here. Perhaps, I need to create a file that would contain that code and then run that file somehow, but I really don't know where I need to create that file and with what extensdion. Can anyone, please, help me with this?

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  • Possible for C++ template to check for a function's existence?

    - by andy
    Is it possible to write a C++ template that changes behavior depending on if a certain member function is defined on a class? Here's a simple example of what I would want to write: template<class T> std::string optionalToString(T* obj) { if (FUNCTION_EXISTS(T->toString)) return obj->toString(); else return "toString not defined"; } So if class T has "toString" defined then it uses it, otherwise it doesn't. The magical part that I don't know how to do is the "FUNCTION_EXISTS" part.

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  • Print PDF from ASP.Net without preview

    - by nmiranda
    Hi, I've generated a pdf using iTextSharp and I can preview it very well in ASP.Net but I need to send it directly to printer without a preview. I want the user to click the print button and automatically the document prints. I know that a page can be sent directly to printer using the javascript window.print() but I don't know how to make it for a PDF. Edit: it is not embedded, I generate it like this; ... FileStream stream = new FileStream(Request.PhysicalApplicationPath + "~1.pdf", FileMode.Create); Document pdf = new Document(PageSize.LETTER); PdfWriter writer = PdfWriter.GetInstance(pdf, stream); pdf.Open(); pdf.Add(new Paragraph(member.ToString())); pdf.Close(); Response.Redirect("~1.pdf"); ... And here I am.

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  • Should downcasting be avoided while using a class hierarchy in C++?

    - by neuviemeporte
    Let's say I'm writing an application which works with projects, and exposes different functionality depending on the type of the project. I have a hierarchy of classes for the different types of projects: class AbstractProject { }; class ProjectA : public AbstractProject { }; class ProjectB : public AbstractProject { }; class ProjectC : public AbstractProject { }; Now, I was planning to have an AbstractProject *_currentProject pointer as a member in the application's main class, pop up a dialog box on startup and based on the selection, do: _currentProject = new ProjectB(); // e.g. Later, I'll have to downcast the pointer to the specific type to utilize the functionality specific to different Project-s. Somehow this makes me feel uneasy. Is there a Better Way of doing this?

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  • Parsing String into multiple variable length String (C#)

    - by Nassign
    I am currently trying to convert a VB6 program into C#. There was extensive use of string splitting into structure. For example, Dim Sample AS String Sample = "John Doe New York Test Comment" Public Type Struct1 Name As String * 15 Address As String * 10 Comment As String * 20 End Type Dim dataStruct As Struct1 Set dataStruct = Sample When the dataStruct is set, it will automatically split value into the 3 structure member. Is there a special function to do this in C#. The only way I know how to do this is thru Attributes/Annotation describing the length and start position of string. Any other suggestion?

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  • mysql stored procedures using php

    - by neo skosana
    I have a stored procedure: delimiter // create procedure userlogin(in eml varchar(50)) begin select * from users where email = eml; end// delimiter ; And the php: $db = new mysqli("localhost","root","","houseDB"); $eml = "[email protected]"; $sql = $db-query("CALL userlogin('$eml')"); $result = $sql-fetch_array(); The error that I get from the browser when I run the php script: Fatal error: Call to a member function fetch_array() on a non-object... I am using phpmyadmin version 3.2.4 and mysql client version 5.1.41. Please help. Thank you.

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  • Manage bad_alloc exception in C++ construtor

    - by Jimmy zhang
    I have Java experience and recently am doing some C++ coding. My question is that if I have class A, in which I have to instantiate class B and class C as two of the member variables of A. If in the constructor of A, should I assume that allocations of class B and C never fail, and handle the bad allocation exception in the destructor of A? If I don't make that assumption, meaning that I add some try catch block to catch bad_alloc of class B and class C, then if the allocation exception occurs, should I do clean up in the constructor of A? What are the recommended practices? If "new" generates a bad allocation, what value does the pointer carry?

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  • Suggestions for performance improvement surrounding sending email notifications?

    - by jcmoney
    It takes around a couple of seconds for my app to execute the code to send an email right now on a test server with nothing much else running. Not sure if this is typical/expected. I'm also using the php framework Kohana's email helper and not php's mail directly out of convenience if that matters. Is it always just better to schedule a cron job to send emails every 5 min or so? Or should I be able to send emails immediately and I'm just not doing something right? What the script does is insert a row into the db and notifies the relevant group that the row was created. The groups are usually < 20 people so I just do a loop calling Kohana's email helper each time for each member of the group.

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  • Binding to object properties in C++

    - by Rich.Carpenter
    I've seen in WPF where you can bind control values to properties of other controls. How is that binding accomplished in C++? For example, if I have a class called Car and a guage control called RPM, how do I tie the value of RPM to the member variable Car.RPM, so that when Car.RPM changes, it is automatically (as in without a specific update call coded by me) reflected by the RPM control? General answers or directions to pertinent resources would be fine also, as I'm just beginning to dabble in C++ and haven't had much Google luck with this particular question.

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  • g++ doesn't think I'm passing a reference

    - by Ben Jones
    When I call a method that takes a reference, g++ complains that I'm not passing a reference. I thought that the caller didn't have to do anything different for PBR. Here's the offending code: //method definition void addVertexInfo(VertexInfo &vi){vertexInstances.push_back(vi);} //method call: sharedVertices[index]->addVertexInfo(VertexInfo(n1index, n2index)); And here's the error: GLUtils/GLMesh.cpp: In member function 'void GLMesh::addPoly(GLIndexedPoly&)': GLUtils/GLMesh.cpp:110: error: no matching function for call to 'SharedVertexInfo::addVertexInfo(VertexInfo)' GLUtils/GLMesh.h:93: note: candidates are: void SharedVertexInfo::addVertexInfo(VertexInfo&)

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  • iphone: Implement delegate in class

    - by Nic Hubbard
    I am trying to call up a modal table view controller using presentModalViewController but I am not sure what to do about the delegate. The following code gives me an error: MyRidesListView *controller = [[MyRidesListView alloc] init]; controller.delegate = self; [self presentModalViewController:controller animated:YES]; [controller release]; Error: Request for member 'delegate' is something not a structure or union Now, I realized there is no delegate property in my MyRidesListView class. So, how would I add a reference to my delegate there? What am I missing here?

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  • Barcode field length

    - by bestattendance
    I'm writing some attendance software. Each member will have an ID card with a barcode which they will use to sign in to events. How long should the barcode field be in my database? I'd like to accept Code 39 and Code 128 barcodes. I know these are variable length codes, so what should I set the max length to? Thanks! EDIT: My clients will be using a variety of third-party barcode printing tools.

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  • How do I release an object allocated in a different AutoReleasePool ?

    - by ajcaruana
    Hi, I have a problem with the memory management in Objective-C. Say I have a method that allocates an object and stores the reference to this object as a member of the class. If I run through the same function a second time, I need to release this first object before creating a new one to replace it. Supposing that the first line of the function is: NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; This means that a different auto-release pool will be in place. The code to allocate the object is as follows: if (m_object != nil) [m_object release]; m_object = [[MyClass alloc] init]; [m_object retain]; The problem is that the program crashes when running the last line of the method: [pool release]; What am I doing wrong ? How can I fix this ? Regards Alan

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  • class which cannot be derived

    - by benjamin button
    I found this code here class Usable; class Usable_lock { friend class Usable; private: Usable_lock() {} Usable_lock(const Usable_lock&) {} }; class Usable : public virtual Usable_lock { // ... public: Usable(); Usable(char*); // ... }; Usable a; class DD : public Usable { }; DD dd; // error: DD::DD() cannot access // Usable_lock::Usable_lock(): private member Could anybody explain me this code?

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  • How to call a function though Control.BeginInvoke in a signal-slot-like fashion?

    - by Dimitri C.
    I'd like a delegate that calls a function in a different thread when it is invoked. Currently, I'm using the following implementation: delegate void someFunctionDelegate(); //... someFunctionDelegate callBackFunction = someForm.SomeFunction; someForm.Invoke(someFunctionDelegate); However, I'd like a more compact form, combining both the someForm instance and the SomeForm.SomeFunction member function. I'm thinking of something like this: var callBackFunction = new AsynchronousCrossThreadDelegate(someForm, SomeForm.SomeFunction); callBackFunction(); // Should call someForm.BeginInvoke(SomeForm.SomeFunction); Is there a way to do so in C#/.NET? Update I'm looking for a solution that will work for functions with 0 or more parameters.

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  • Help with Magento and related products

    - by Anthony
    I have a customer product page that literally lives beside the catalog/product/view.phtml page. It's basically identical to that page with a few small exceptions. It's basically a 'product of the day' type page so I can't combine it with the regular product page since I have to fetch the data from the DB and perform a load to get the product information $_product = Mage::getModel('catalog/product')->load($row['productid']); To make a long story short, everything works (including all children html blocks) with the singular exception of the related products. After the load I save the product into the registry with Mage::register('product', $_product); and then attempt to load the related products with: echo $this->getLayout()->createBlock('catalog/product_view')->setTemplate('catalog/product/list/related.phtml')->toHtml();` All of which give back the error: Fatal error: Call to a member function getSize() on a non-object in catalog/product/list/related.phtml on line 29`, and line 29 is <?php if($this->getItems()->getSize()): ?>`. Any help getting the relateds to load would be appreicated.

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  • Using a class with const data members in a vector

    - by Max
    Given a class like this: class Foo { const int a; }; Is it possible to put that class in a vector? When I try, my compiler tells me it can't use the default assignment operator. I try to write my own, but googling around tells me that it's impossible to write an assignment operator for a class with const data members. One post I found said that "if you made [the data member] const that means you don't want assignment to happen in the first place." This makes sense. I've written a class with const data members, and I never intended on using assignment on it, but apparently I need assignment to put it in a vector. Is there a way around this that still preserves const-correctness?

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  • C++ associative array with arbitrary types for values

    - by Gerald Kaszuba
    What is the best way to have an associative array with arbitrary value types for each key in C++? Currently my plan is to create a "value" class with member variables of the types I will be expecting. For example: class Value { int iValue; Value(int v) { iValue = v; } std::string sValue; Value(std::string v) { sValue = v; } SomeClass *cValue; Value(SomeClass *v) { cValue = c; } }; std::map<std::string, Value> table; A downside with this is you have to know the type when accessing the "Value". i.e.: table["something"] = Value(5); SomeClass *s = table["something"].cValue; // broken pointer Also the more types that are put in Value, the more bloated the array will be. Any better suggestions?

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  • Find a variable with a given value in VS2008

    - by Aaron
    I have an instance variable with several members, many of which have their own members and so on. Using the debugger and watch variables, I found a string variable with a specific value that I need by diving into this variable's members. However, after spending some time on other things and coming back to this, I am now unable to find where this value is located. When I have my application paused, is there a way to search the values of variables in the current context for a given value? To clarify, if I have the given structure: myVariable | |--aMember1 | |--subMember = "A value" | |--aMember2 |--subMember = "Another value" Is there a way (possibly using the watch list in VS debugger) to search myVariable for any member or submember with the value "A value", returning to me the path myVariable->aMember->subMember?

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  • Lifetime of implicitly casted temporaries

    - by Answeror
    I have seen this question. It seems that regardless of the cast, the temporary object(s) will "survive" until the fullexpression evaluated. But in the following scenario: void foo(boost::tuple<const double&> n) { printf("%lf\n", n.get<0>()); } int main() { foo(boost::tuple<const double&>(2));//#1 foo(boost::make_tuple(2));//#2 return 0; } 1 run well, but 2 do not. And MSVC gave me a warning about 2: "reference member is initialized to a temporary that doesn't persist after the constructor exits" Now I am wondering why they both make a temporary "double" object and pass it to boost::tuple<const double&> and only 2 failed.

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