When Does ObjC Object in C++ Class dealloc - Everett

References
Summary

When using Objective C++, can use C++’s struct or class to store Objective C objects.

For example:

struct CppStruct {
    MyObject *obj;
};

Then suddenly think, if CppStruct destructs, will MyObject dealloc? Don’t need to think much, definitely will. But how is it done?

Write code to verify,

@interface MyObject : NSObject
@end
@implementation MyObject
- (instancetype)init {
    self = [super init];
    if (self) {
        NSLog(@"MyObject init");
    }
    return self;
}
- (void)dealloc {
    NSLog(@"MyObject dealloc");
}
@end

struct CppStruct {
    MyObject *obj;
    CppStruct() {
        NSLog(@"CppStruct constructor");
    }
    ~CppStruct() {
        NSLog(@"CppStruct destructor");
    }
};

CppStruct * CreateStruct() {
    CppStruct * s = new CppStruct();
    s->obj = [[MyObject alloc] init];
    return s;
}

void FreeStruct(CppStruct *s) {
    delete s;
}

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        CppStruct *s = CreateStruct();
        FreeStruct(s);
    }
    return 0;
}

Output below