Objective-C instance into C++ class

Question

How I can instantiate a Objective-c class into CPP class?

for example my CPP class:

class Foo{
public:
    Foo();
private:
    MyObjcClass* myObjcClass; //it does not work
}

how I can do this?

note I using .m for Objective-C and .cpp for C++.

Thanks a lot!

Despite you not wanting it, you **are going to need** to use the `.mm` extension if you want this. — , Nov 07 '12 at 19:12
@H2CO3 because that CPP class is used mutually for IOS and Android, because this I need a cpp class, that Obj-c object received an ifdef in late. — ademar111190, Nov 07 '12 at 19:16
in this case, you can pass `-x obj-c++` as a compiler flag to clang. — , Nov 07 '12 at 19:18
@H2CO3 thanks but declaring as follow id myObjcClass; instead MyObjcClass* myObjcClass; works fine without compiler flags :) thanks a lot! — ademar111190, Nov 07 '12 at 19:31

justin · Accepted Answer · 2012-11-07T20:47:03.220

3

Either

compile as Objective-C++
or declare it as id.

If you use id, you should introduce the type in your definitions, e.g.:

// Foo.mm
Foo::~Foo() {
  MyObjcClass * a = this->myObjcClass;
  [a release];
}

In general, you should preserve the type (MyObjcClass) and avoid using id, but declaring the variable as id is compatible with C and C++, so you can use id to avoid compiling everything that includes Foo.hpp as ObjC++.

edited Nov 07 '12 at 20:47

answered Nov 07 '12 at 19:17

justin

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@ademar111190 perhaps you are looking for: `Foo::Foo() : myObjcClass([MyObjcClass new]) {}`? if you chose `id`, only `Foo` would need to change to compile as ObjC++, but everything that saw Foo would need just C++. – justin Nov 07 '12 at 19:23
1

perfect!!! dataDownload = [DataDownload new]; work too, but a very thank you justin :) – ademar111190 Nov 07 '12 at 19:30

score 1 · Answer 2 · answered Nov 07 '12 at 19:19

1

There are two ways to do this. The sane way is to use Objective-C++. You can either do this with files that have a .mm extension or you can change your build settings. The default is to compile based on the file extension, but you can force it use Objective-C++ on a .cpp or .m file.

The crazy way is to use the raw Objective-C interface in objc.h.

answered Nov 07 '12 at 19:19

IronMensan

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Both true, but there's a third way, which is to just use `id` in all the pure C++ code, and move the code that must be ObjC (or ObjC++) into separate files, as justin suggests. – abarnert Nov 07 '12 at 20:12

Objective-C instance into C++ class

2 Answers2