constructor

问题 Can anyone explain why does non-single parameter constructor marked as explicit compile? As far as I understand this is absolutely useless keyword here, so why does this compile without error? class X { public: explicit X(int a, int b) { /* ... */} }; 回答1: In C++03, and in this particular case, it makes no sense for a two parameter constructor to be marked explicit . But it could make sense here: explicit X(int i, int j=42); So, marking a two parameter constructor with explicit does not have

问题 Can anyone explain why does non-single parameter constructor marked as explicit compile? As far as I understand this is absolutely useless keyword here, so why does this compile without error? class X { public: explicit X(int a, int b) { /* ... */} }; 回答1: In C++03, and in this particular case, it makes no sense for a two parameter constructor to be marked explicit . But it could make sense here: explicit X(int i, int j=42); So, marking a two parameter constructor with explicit does not have

问题 I experienced an issue that in the class constructor while I was using this pointer, but this pointer happen to be NULL at that time. for example MyClass::MyClass() { //this pointer happen to be NULL in this case, and it crash in teh m_callbackfunc because it does not handle null input. m_callbackFunc(this); } I wonder why this pointer can be null? and in which case this pointer can be null? 回答1: The only way a this pointer can be NULL is if some code in the program has exhibited undefined

问题 I experienced an issue that in the class constructor while I was using this pointer, but this pointer happen to be NULL at that time. for example MyClass::MyClass() { //this pointer happen to be NULL in this case, and it crash in teh m_callbackfunc because it does not handle null input. m_callbackFunc(this); } I wonder why this pointer can be null? and in which case this pointer can be null? 回答1: The only way a this pointer can be NULL is if some code in the program has exhibited undefined

问题 I'm using TypeScript to create some classes with KnockoutJS, with the data being loaded from some JSON returned by WebAPI. The problem is I wanted to copy the JSON values into my TypeScript class from the constructor: but if I do this just at the base class, the inherited properties have not been defined and so are not initialised. Example We want to create an inventory item from a JSON response: { Name: "Test", Quantity:1, Price: 100 } I have a base class Product and an inherited class

问题 Is it possible to create a mock from a class that doesn't provide a no-argument constructor and don't pass any arguments to the constructor? Maybe with creating IL dynamically? The background is that I don't want to define interfaces only for testing. The workaround would be to provide a no-argument constructor for testing. 回答1: Sure thing. In this example i'll use Moq, a really awesome mocking library. Example: public class MyObject { public MyObject(object A, object B, object C) { // Assign

问题 Compiler: ifort version 12.1.5 I'm writing some Fortran code and I'd like to make use of some F2003 OOP features, but I'm hitting some stumbling blocks. Paring down the example, I wish to have two derived types A and B, each of which have a pointer to instances of the other. In Fortran, circular dependencies between modules are explicitly disallowed, so these two types would have to reside in the same module. This compiles: module testModule implicit none type A type(B),pointer :: b1 end type

问题 So, I've been looking at boost::array but it does require default constructor defined. I think the best way of filling this array with data, would be through a push_back(const T&) method. Calling it more times than SIZE (known at compile-time) would result in assert or exception, depending on build configuration. This way it would always contain meaningful data. Does anyone know efficient, portable, reliable implementation of this concept? 回答1: Well, I would have thought that someone would

问题 I have a JavaScript class representing a car, which is constructed using two parameters, which represent the make and model of the car: function Car(make, model) { this.getMake = function( ) { return make; } this.getModel = function( ) { return model; } } Is there a way to verify that the make and model supplied to the constructor are strings? For example, I want the user to be able to say, myCar = new Car("Honda", "Civic"); But I don't want the user to be able to say, myCar = new Car(4, 5.5)

问题 What does dot class mean in the parameter passed to Constructor I am using jgrapht for the first time . I have this question What are we passing to the constructor of the DefaultDirectedGraph class? I mean what does DefaultEdge.class means ? There is no static field with that name inside that class. I mean what is actual being passed to the contructor of that class. What does the dot class mean there ? DirectedGraph<String, DefaultEdge> g = new DefaultDirectedGraph<String, DefaultEdge>