constructor

问题 Is the order of the initializers for a class' constructor significant? So say I have: class MyClass : BaseClass { int a, b, c; public: MyClass(int); } e.g. 1: MyClass::MyClass(int forBase) : a(7), b(14), c(28), BaseClass(forBase) { } e.g. 2: MyClass::MyClass(int forBase) : BaseClass(forBase), a(7), b(14), c(28) { } Would example 1 do something different to example 2? 回答1: Would example 1 do something different to example 2? No . Initialisation order is dictated by the standard, not by the

问题 I come across the rule (section N3797::12.8/11 [class.copy] ) An implicitly-declared copy/move constructor is an inline public member of its class. A defaulted copy/ move constructor for a class X is defined as deleted (8.4.3) if X has: [...] — any direct or virtual base class or non-static data member of a type with a destructor that is deleted or inaccessible from the defaulted constructor, or [...] But I can't get the point of deleted destructor appearing in a virtual or direct base class

问题 According to the SCJP6 (Page 507) i found that instance variables are assigned default values before the superclass constructors complete, i tried an example in Debugg mode but i saw that the super contractor runs before instance variables get their default values, could any one explain that to me ? Example i used in case someone want to try it: package courseExercise; class test { test() { System.out.println("Super Constructor run"); } } public class Init extends test { private Integer i = 6

问题 This is a problem I come across often. The following examples illustrates it: struct A { int m_SomeNumber; }; struct B { B( A & RequiredObject ); private: A & m_RequiredObject; }; struct C { C( ); private: A m_ObjectA; B m_ObjectB; }; The implementation of the constructor of C looks something like this: C::C( ) : B( m_ObjectA ) { } Since the order of initialization is not defined, m_ObjectA might be uninitialized when the constructor of m_ObjectB is called, resulting in undefined behavior.

问题 This is a problem I come across often. The following examples illustrates it: struct A { int m_SomeNumber; }; struct B { B( A & RequiredObject ); private: A & m_RequiredObject; }; struct C { C( ); private: A m_ObjectA; B m_ObjectB; }; The implementation of the constructor of C looks something like this: C::C( ) : B( m_ObjectA ) { } Since the order of initialization is not defined, m_ObjectA might be uninitialized when the constructor of m_ObjectB is called, resulting in undefined behavior.

问题 This is what I'm doing: @Aspect public class MethodLogger { @Around("(execution(* *(..)) || initialization(*.new(..))) && @annotation(Foo)") public Object wrap(ProceedingJoinPoint point) throws Throwable { // works fine, but only for methods } } The snippet works fine, but only for method calls. This is what AspectJ maven plugin is saying after applying the aspect (not during its compilation, which works just fine): around on initialization not supported (compiler limitation) Any workaround?

问题 I haven't worked with c++ in a while, but I just started a project with it. This may not be possible, but Im trying to create a template class with an array that sets its size to the value of a constant which i'm trying to set with the constructor. This is the code of the constructor: Tarray(int s): start_size(s){ } This is the code that sets the array size: const int start_size; T this_array[start_size]; This is the entire file: #ifndef TARRAY_H_ #define TARRAY_H_ template<typename T> class

问题 If a have a class with both standard and copy constructors class Ex{ //constructor definitions } and a function that takes it as an argument (by value) void F(Ex _exin){...} take the following piece of code: Ex A; F(A); //F's parameter is copy constructed from A F(Ex()); //F's parameter uses the default constructor In the third line I'm passing to F a new (temporary) object of the Ex class using the default constructor. My question is: after this new object is created is it also copy

问题 I'm trying to figure out the correct syntax to use the pipe operator |> into the creation of an object. Currently I'm using a static member to create the object and just piping to that. Here is the simplified version. type Shape = val points : Vector[] new (points) = { points = points; } static member create(points) = Shape(points) static member concat(shapes : Shape list) = shapes |> List.map (fun shape -> shape.points) |> Array.concat |> Shape.create What I want to do ... static member

问题 I'm trying to figure out the correct syntax to use the pipe operator |> into the creation of an object. Currently I'm using a static member to create the object and just piping to that. Here is the simplified version. type Shape = val points : Vector[] new (points) = { points = points; } static member create(points) = Shape(points) static member concat(shapes : Shape list) = shapes |> List.map (fun shape -> shape.points) |> Array.concat |> Shape.create What I want to do ... static member