constructor

问题 I noticed that similar questions have been asked before but I did not find any detailed examples. I have a winform program, its constructor has a parameter cn: public AddFailure(ProSimConnect cn)// constructor in winform { this.connection = cn; InitializeComponent(); ... } Now I need to simulate it in a UserControl in WPF and put it into MainWindow. In MainWindow.xaml: <Border ...> <IOS:Core_System/> </Border> I want to do this but I know I can't because it shouldn't have any parameter:

问题 This question already has answers here : Why can a enum have a package-private constructor? (2 answers) Closed 4 years ago . Recently I'm quite oftenly using Enumerations. So I wonder... Is there any difference between a private Enum constructor and a enum constructor withour any visibility modifier (package-private)? 回答1: According to java docs The constructor for an enum type must be package-private or private access. but Accroding to the JLS If no access modifier is specified for the

问题 Here is the annotation: @Target(value = ElementType.TYPE) @Retention(value = RetentionPolicy.RUNTIME) @Inherited public @interface MyAnnotation { String name(); } Here is one annotated class: @MyAnnotation(name="foo") public class ClassA { public ClassA() { // Do something } } Here is a second annotated class: @MyAnnotation(name="bar") public class ClassB { public ClassB(String aString) { // Do something } } I am looking for an aspectj pointcut that correctly matches the constructors for

问题 Foo f1 = Foo(); // (1) Ok Foo f2 = Foo; // (2) Compiler error Foo *p1 = new Foo(); // (3) Ok Foo *p2 = new Foo; // (4) Ok. Why?? I was wondering why there exists two ways to initialize pointers. It looks a little inconsistent. Is there some logical reason, and if so, what? Or, maybe it's some kind of legacy? And if so, What is the origin of such notation? 回答1: It's a bit... complicated, to say the least. When dealing with objects, both notations are equivalent. When dealing with primitive

问题 Can someone please explain the following constructor syntax to me. I haven't come across it before and noticed it in a colleagues code. public Service () : this (Service.DoStuff(), DoMoreStuff()) { } 回答1: It chains to another constructor in the same class. Basically any constructor can either chain to another constructor in the same class using : this (...) , or to a constructor in the base class using : base(...) . If you don't have either, it's equivalent to : base() . The chained

问题 While doing my programming assignments, I seem to be stumbling over basic C++ concepts. I found the bug in my program and it was caused by my destructor running more times than I expected. Here is a code sample demonstrating what I am doing wrong, down to the bare essentials. #include <iostream> using namespace std; class A { public: A(int num) { number = num; cout << "A constructed with number " << number << ".\n"; } ~A() { cout << "A destructed with number " << number << ".\n"; } private:

问题 Is there a way to force a derived class to use the constructor of the abstract base class? It must not be a real constructor, I have an open mind about creative solutions. class Abstract { private: int Member; string Text; public: Abstract(int Member, string Text) { this->Member = Member; this->Text = Text; } // e.g. defining virtual functions } For example my abstract class has some private members which every derived class should also have. And they should be defined in the constructor,

问题 Can anybody explain to me the difference between Complex a; and Complex b(); ? #include<iostream> class Complex { public: Complex() { std::cout << "Complex Constructor 1" << std::endl; } Complex(float re, float im) { std::cout << "Complex Constructor 2" << std::endl; } ~Complex() { std::cout << "Complex Destructor" << std::endl; } }; int main() { Complex a; std::cout << "--------------------------" << std::endl; Complex b(); std::cout << "--------------------------" << std::endl; Complex c(0

问题 Can anybody explain to me the difference between Complex a; and Complex b(); ? #include<iostream> class Complex { public: Complex() { std::cout << "Complex Constructor 1" << std::endl; } Complex(float re, float im) { std::cout << "Complex Constructor 2" << std::endl; } ~Complex() { std::cout << "Complex Destructor" << std::endl; } }; int main() { Complex a; std::cout << "--------------------------" << std::endl; Complex b(); std::cout << "--------------------------" << std::endl; Complex c(0

问题 I want to implement my own matrix-class that inherits from numpy's matrix class. numpy's matrix constructor requires an attribute, something like ("1 2; 3 4'") . In contrast, my constructor should require no attributes and should set a default attribute to the super-constructor. That's what I did: import numpy as np class MyMatrix(np.matrix): def __init__(self): super(MyMatrix, self).__init__("1 2; 3 4") if __name__ == "__main__": matrix = MyMatrix() There must be a stupid mistake in this