Constructors in Abstract Classes?
Possible Duplicate: Abstract class constructor in Java When we can't create an instance of abstract class, what is the purpose of a constructor? ...
constructor
About constructors
Hi all, I got a question about Constructors.I think constructors are all just our convenience instead of setter methods,right? So for an object , the properties you think important(such as required fields in a webform)are passed as parameters into constructor. Is there any criteria that these many number of parameters should be pa...
How do you use the non-default constructor for a member?
I have two classes class a { public: a(int i); }; class b { public: b(); //Gives me an error here, because it tries to find constructor a::a() a aInstance; } How can I get it so that aInstance is instantiated with a(int i) instead of trying to search for a default constructor? Basically, I want to con...
C++ constructor and an initializer list
does C++ allow to initialize struct using initializer list, {}, if struct has a defined constructor? could not find an answer, but g++ does not seem to allow it. struct r { int a; }; struct s { int a; s() : a(0) {} }; r = { 1 }; // works s = { 1 }; // does not work ...
JavaScript constructors
I do not understand quite completely how to apply constructors on this object creation method: var MyObject = { ... }; I know that you can do: var MyObject = new Object(); MyObject.prototype.constructor = function(props) { ... } or... function MyObject(prop1, prop2) { this.prop1 = prop1; ... } Can I do something like t...
WPF: Event Handlers in Codebehind's Constructor not hooking up.
Hi there! Sit Rep I have a WPF app. In the constructor of the (C#) code-behind I attach a button event-handler. Problem is, it doesn't attach! But if I attach it via clicking a UI button, then the button works fine. Also, of course, if I attach it in the button's XAML it works too. So, it appears that the prob is attaching the handler...
What is the use of creating a constructor for an abstract class in Java?
I would like to know what purpose a constructor for an abstract class serves; as we do not instantiate abstract classes, why would we ever need such a constructor? ...
Java: Class<T> and Class: Difference when used from within/ outside of the class
Hi, I have a class that needs to use a Class<T> parameter (see my previous semi-related question). It is: public class BaseTable<T extends TableEntry> { protected Class<T> mClass; ... public BaseTable(int rows, int cols, Class<T> clasz) { ... mClass = clasz; } public BaseTable(int rows, int col...
how to use my_alloc for _all_ new calls in C++?
Imagine I'm in C-land, and I have void* my_alloc(size_t size); void* my_free(void*); then I can go through my code and replace all calls to malloc/free with my_alloc/my_free. How, I know that given a class Foo, I can do placement new; I can also overload the new operator. However, is there a way to do this for all my C++ classes? (...
Sanitize GET data through PHP constructor
I have the following constructor: public function __construct(){ foreach($_GET as $key=>$value){ $_GET[$key] = addslashes($value); } $this->get = $_GET; } and it's used like so: $app->get['id'] Where 'id' is the parameter being passed through the URL.Is there a good way to sanitize all the data through the const...
How to handle exceptions thrown during the instantiation of a WPF Application?
I'm using the following code to display unhandled exceptions in a WPF application: public MyApplication() { this.DispatcherUnhandledException += (o, e) => { var exceptionMessage = new ExceptionWindow(); exceptionMessage.ExceptionMessage.Text = e.Exception.Message; exce...
C++ templated constructor won't compile
How come I can't instantiate an object of type Foo with above constructor? I have a class Bar that uses an internal typedef (as a workaround for "template typedefs") and intend to use it in a constructor as below (CASE 1). However, I don't seem to get it to compile. Is this legal C++? CASE 2 seems to suggest the problem is related to th...
Can I designate a Java-like 'constructor' in c?
I want to 'construct' (read: malloc and memset) my hashtable in c. To do this, I created a function as follows: int maketable(struct hash_entry **table, int size){ table = (struct hash_entry **)malloc(size*sizeof(struct hash_entry *)); int i = 0; for (; i<size; i++) { memset(table[i], '\0', sizeof(struct hash_entry...
Why can I not call my class's constructor from an instance of that class in C++?
When can an object of a class call the destructor of that class, as if it's a regular function? Why can't it call the constructor of the same class, as one of its regular functions? Why does the compiler stops us from doing this? For example: class c { public: void add() ; c(); ~c() ; }; void main() { c objC ; objC.add() ;...
Lazy/multi-stage construction in C++
What's a good existing class/design pattern for multi-stage construction/initialization of an object in C++? I have a class with some data members which should be initialized in different points in the program's flow, so their initialization has to be delayed. For example one argument can be read from a file and another from the network...
Constructor of Derived Class
I had originally created a set of array classes that allowed me to initialize the different arrays in the constructor. For example, Vector A(2,0); would create a vector of length 2 with each element being equal to zero. For a number of reasons I've decided to pitch that class and go with something a little more commercial. I would l...
Is this ambiguous or is it perfectly fine?
Is this code ambiguous or is it perfectly fine (approved by standards/has consistent behavior for any compilers in existence)? struct SCustomData { int nCode; int nSum; int nIndex; SCustomData(int nCode, int nSum, int nIndex) : nCode(nCode) , nSum(nSum) , nIndex(nIndex) {} }; edit: yes, I am...
Multiple constructors in python?
Possible Duplicate: What is a clean, pythonic way to have multiple constructors in Python? Is it not possible to define multiple constructors in Python, with different signatures? If not, what's the general way of getting around it? For example, let's say you wanted to define a class City I'd like to be able to say someCity...
C#/vb.net type mismatch looking up a constructor by reflection (Integer() vs System.Int32[])
I'm passing a type name and some parameters from C# code into a navigation framework written in VB. The navigation framework looks for a constructor on the type that matches the parameters passed in using Type.GetConstructor(Types()). The constructor that I'm looking for expects an array of integers -- Integer() in vb. But it gets an ...
How should a constructor act when given invalid parameters?
If a class has a constructor which takes some value object as parameter and relies on this to do its initialization. How should it react if this object is null? class SomeClass { private SomeData _data; public SomeClass(SomeValueObject obj) { _data = obj.Data; } } This is one example, but in general: How shou...