Question

I’m trying to create a C array of objective C NSStrings using malloc. I’m not doing it right, but I don’t think I’m far off. Maybe someone can point me in the right direction.
Let’s say we want 5 strings in our array for the sake of argument.

Interface:

@interface someObject : NSObject {
    NSString **ourArray;
}
@property () NSString **ourArray;
@end

Implementation:

@implementation someObject
@synthesize ourArray;

-(id)init {
    if((self = [super init])) {
        self->ourArray = malloc(5 * sizeof(NSString *));
    }
    return self;
}

-(NSString *)getStringAtPos3 {
    if(self.ourArray[3] == nil) {
        self.ourArray[3] = @"a string";
    }
    return self.ourArray[3];
}
@end

When I set a breakpoint in getStringAtPos3 it doesn’t see the array element as nil so it never goes into the if statement.

Answer 1

I figured out the problem – I should have been using calloc, not malloc. While malloc simply allocates the memory, calloc

contiguously allocates enough space for count objects that are size bytes of memory each and returns a pointer to the allocated memory. The allocated memory is filled with bytes of value zero.

This means you get an array of nil objects essentially as in objective c 0x0 is the nil object.