How to retrieve Objective-C variable from C++ method?

Question

I mixed some C++ codes with Objective-C in class with .mm extension.

I synthesized some variables in Objective-C, and I want to retrieve those variables in C++ methods. How to do that?

I tried [self aVariable], this->aVariable to retrieve the synthesized variables, but failed.

Pass them as parameters, perhaps? – Hot Licks Jan 31 '14 at 22:23 — Hot Licks, Jan 31 '14 at 22:23

score 1 · Answer 1 · answered Nov 18 '10 at 09:21

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You cannot use self in a C++ class. this->aVariable doesn't say anything. It doesn't say whether you are trying to call a method. In fact it doesn't do anything with aVariable.

I assume the method is attached to an objective-C object. If so call it as follows from the C++ class:

[aVariable <method>];

answered Nov 18 '10 at 09:21

Goz

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Hey, I don't understand what you mean. Would you please explain in more details ? – user403015 Nov 18 '10 at 09:54
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@User: TBH I'm not sure what YOU are doing ... post some code – Goz Nov 18 '10 at 10:21

score -1 · Accepted Answer · edited May 23 '17 at 12:29

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I fixed my problem after reading this post:

Calling Objective-C method from C++ method?

edited May 23 '17 at 12:29

Community

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answered Nov 18 '10 at 13:39

user403015

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Why does `self` need to be typed as `void*`? Just do `void doSomething(id self)`. Of course, you could have understood all of this instantly by actually knowing any C, or by reading Apple's guide to Objective-C. – Jonathan Sterling Nov 18 '10 at 16:23
I tried your suggestion - void doSomething(id self), but it does not compile. "void *self" works, but I don't know why, since I am new in C++. – user403015 Nov 18 '10 at 16:57
@user403015: what error(s) do you get when compiling? If you give us sufficient information, we can help you. – outis Nov 19 '10 at 00:51

How to retrieve Objective-C variable from C++ method?

2 Answers2