You can't put two __construct functions with unique argument signatures in a PHP class. I'd like to do this: class Student { protected $id; protected $name; // etc. public function __construct($id){ $this->id = $id; // other members are still uninitialized } public function __construct($row_from_databas...
Say you have this shell of a class: public class Number { private int value; public Number() : this(0) {} public Number(int initialValue) : this(initialValue, 0, 100) {} public Number(int initialValue, int minimumValue, int maximumValue) { if (minimumValue > maximumValue) throw ...
I'm a little confused about what is going on in Perl constructors. I found these two examples perldoc perlbot. package Foo; #In Perl, the constructor is just a subroutine called new. sub new { #I don't get what this line does at all, but I always see it. Do I need it? my $type = shift; #I'm turning the array of inputs into a has...
Recently I've seen an example like the following: #include <iostream> class Foo { public: int bar; Foo(int num): bar(num) {}; }; int main(void) { std::cout << (new Foo(42))->bar << std::endl; return 0; } What does this strange : bar(num) mean? It somehow seems to initialize the member variable but I've never seen this syntax...
I want a few constructors defined in a PHP class. However, my code for the constructors is currently very similar. I would rather not repeat code if possible. Is there a way to call other constructors from within one constructor in a php class? Is there a way to have multiple constructors in a PHP class? function __construct($service, $...
Howdy all, I'm trying to create a constructor for a custom type, but for some reason, it's trying to call, what I'm guessing is the constructor in the constructor definition of anotehr class.. Couldn't find anything which fits the same symptoms I'm having in any other questions, also as I may not know what I'm looking for. When I call:...
I've just been reading this question which is about giving an ActiveRecord model's date field a default value. The accepted answer shows how to set the default value from within the controller. To my mind, this sort of business logic really belongs in the model itself. Then I got to thinking how if this were Java I'd probably set the in...
For example is this correct: class C { private: C(); C(const & C other); } or you should rather provide definition(s): class C { private: C() {}; C(const & C other) {}; } ? Thanks for the current answers. Let's extend this question - does compiler generate better code in one of this examples? I can im...
I'm getting some errors when compiling my program. They relate to the constructor and destructor of my class Instruction. Errors are: /tmp/ccSWO7VW.o: In function `Instruction::Instruction(std::basic_string<char, std::char_traits<char>, std::allocator<char> >, int)': ale.c:(.text+0x241): undefined reference to `vtable for Instruction' ...
type Foo = class inherit Bar val _stuff : int new (stuff : int) = { inherit Bar() _stuff = stuff } end I want to add this code in above constructor: if (stuff < 0) then raise (ArgumentOutOfRangeException "Stuff must be positive.") else () How can I achieve this in F#...
Hello stackoverflow! Long-time reader first time writer here. I am currently undertaking a conversion from to the use of Ninject to the current release of Castle Windsor for a simple C# .NET application. For the most part, the conversion has gone well and the implementation of the containers has executed flawlessly. I am however hav...
There are different ways to set a member variable from the constructor. I am actually debating how to properly set a final member variable, specifically a map which is loaded with entries by a helper class. public class Base { private final Map<String, Command> availableCommands; public Base() { availableCommands = Helpe...
Let's say I have the following class which I am not allowed to change: public class C { public C() { CreateSideEffects(); } public void M() { DoSomethingUseful(); } } and I have to call M without calling the constructor. Is it possible? ...
Hello everybody. Here is the little code snippet: class A { public: A(int value) : value_(value) { cout <<"Regular constructor" <<endl; } A(const A& other) : value_(other.value_) { cout <<"Copy constructor" <<endl; } private: int value_; }; int main() { A a = A(5); } I assumed that output ...
Hi, I've a little doubt over this line: An anonymous class cannot define a constructor then, why we can also define an Anonymous class with the following syntax: new class-name ( [ argument-list ] ) { class-body } ...
I'm trying to create a child class of TForm with a special constructor for certain cases, and a default constructor that will maintain compatibility with current code. This is the code I have now: interface TfrmEndoscopistSearch = class(TForm) public /// original constructor kept for compatibility constructor Create(AO...
Is there any way to require that a class have a default (no parameter) constructor, aside from using a reflection check like the following? (the following would work, but it's hacky and reflection is slow) boolean valid = false; for(Constructor<?> c : TParse.class.getConstructors()) { if(c.getParameterTypes().length == 0) { ...
While reading some stuff on the pImpl idiom I found something like this: MyClass::MyClass() : pimpl_( new MyClassImp() ) First: What does it mean? Second: What is the syntax? Sorry for being such a noob. ...
Call me crazy, but I'm the type of guy that likes constructors with parameters (if needed), as opposed to a constructor with no parameters followed by setting properties. My thought process: if the properties are required to actually construct the object, they should go in the constructor. I get two advantages: I know that when an ob...
Please tell me why the constructor not returns value. i want a perfect technical reason to explain my students that why constructor not have any return type. ...