How to forward an overloaded constructor call to another constructor in C ++ / CLI

Question

I know that there is no way to do this in pure C ++ , but I was wondering if it is possible to call the constructor from another constructor initialization list in C ++ / CLI, it is also possible to do this in C #.

Example:

ref class Foo { Foo() {} Foo(int i) : Foo() {} } 

Answer 1

It is called the "delegating constructor." It is not yet available in this language. But there is an official proposal, you will find it in Appendix F.3.1 of the language specification . Given Microsoft's stance on C ++ / CLI, this is unlikely to be released any time soon.

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UPDATE: delegating constructors had a life outside the sentences in this application, they were added to the standard C ++ 11 language specification. Microsoft is working on introducing C ++ 11 add-ons. Delegating constructors have finally done this for VS2013. And they also work in C ++ / CLI in this release.

Answer 2

You can do the following

 ref class A { public: A(int p) : p(p) { this->A::A(); } A() : p(1) {} int p; }; 

Invalid C ++ code, but VC will compile it :)

Answer 3

Just stumbled on the same issue. In my case, I am using VS2010.

It is clear that VS2010 will never be updated in order to fully implement C ++ 11, use VS2015 if you need better compliance with the standard (what I do when I can). But for some (old) projects, I still have to use VS2010.

An approach that works in many cases (for me) is to use a private function with all the common initialization code. Example:

 class A { private: void Inidialise() { /* common initialisation here */ } public: A() { Initialise(); /* specific initialisation for A() here */ } A(bool a) { Initialise(); /* specific initialisation for A(bool) here */ } A(int b) { Initialise(); /* specific initialisation for A(int) here */ } /* etcetera */ } 

It does not solve all the "problems" and does not prevent all cases of code duplication, but it is of great importance.

Answer 4

When you said, “I know there is no way to do this in pure C ++,” you were wrong. This can be done in C ++. You can use the layout operator for this.

 class A { public: A(int p) : p(p) { new(this)A(); } A() : p(1) {} int p; };