Question

I would like to store (pointers to) dynamic arrays as the instance variables in objects, and be able to initialize the arrays to custom size. Like in this simple code:

@interface DummyClass: NSObject {
float * X;
}
@property float * X;
@end

@implementation DummyClass
@synthesize X;
-(id) init {
    [super init];
    X = malloc(100*sizeof(float));
}
@end

int main(int argc, const char * argv) {
    float * mypointer;
    DummyClass * myclass = [[DummyClass alloc] init];
    mypointer = myclass.X;
    mypointer[0] = 1;
    NSLog(@"Vallue assigned succesfully");
    getchar();
    return 0;
}

This gives “Segmentation fault” error when trying to assign value to mypointer[0]. What’s the proper way of storing and accessing dynamic arrays within objects?

Answer 1

Your init method needs to return something:

-(id) init {
    self = [super init];
    X = malloc(100*sizeof(float));
    return self;
}

Your program runs fine for me here after making that change (and after correcting the signature of main). You should have had a warning or error about that mistake, though. How did you build & test your example program?