CODEWITHSUNDEEP
objective-ccarrays
rob5408
rob5408

Reputation: 2982

Initializing Objective-C class ivar that is a C array

I have an ivar in my Obj-C class that's a C array (I'm not interested in making it an Obj-C property). Simple enough. Now in my class's init method I'd like to seed this array with some values using the C array shorthand init as seen in my .m below. But I'm fairly positive this is creating a local variable by the same name and not initializing my instance variable. I can't put my array init in the interface and I cannot declare an ivar in an implementation. Am I just stuck doing some sort of deep copy over or do I have another option?

In GameViewController.h

#define kMapWidth 10
#define kMapHeight 10

@interface GameViewController : UIViewController
{
    unsigned short map[kMapWidth * kMapHeight];
}

@end

In GameViewController.m

- (id)init
{
    if ((self = [super init]))
    {
        unsigned short map[kMapWidth * kMapHeight] = { 
            1,1,1,1,1,1,1,1,1,1,
            1,0,0,0,0,0,0,0,0,1,
            1,0,0,0,0,0,0,0,0,1,
            1,0,0,0,0,0,0,0,0,1,
            1,0,0,0,0,0,0,0,0,1,
            1,0,0,0,0,0,0,0,0,1,
            1,0,0,0,0,0,0,0,0,1,
            1,0,0,0,0,0,0,0,0,1,
            1,0,0,0,0,0,0,0,0,1,
            1,1,1,1,1,1,1,1,1,1,
        };
    }
    return self;
}

Upvotes: 4

Views: 725

Answers (1)

Mehrdad Afshari
Mehrdad Afshari

Reputation: 421988

You are right. What you are doing is initializing a local variable, shadowing the instance variable. You can initialize a local array and memcpy it to the instance variable:

static const unsigned short localInit[] = { 
        1,1,1,1,1,1,1,1,1,1,
        1,0,0,0,0,0,0,0,0,1,
        1,0,0,0,0,0,0,0,0,1,
        1,0,0,0,0,0,0,0,0,1,
        1,0,0,0,0,0,0,0,0,1,
        1,0,0,0,0,0,0,0,0,1,
        1,0,0,0,0,0,0,0,0,1,
        1,0,0,0,0,0,0,0,0,1,
        1,0,0,0,0,0,0,0,0,1,
        1,1,1,1,1,1,1,1,1,1,
};

memcpy(map, localInit, sizeof(localInit));

Upvotes: 5

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