Question

I have written code for an animation that shakes a UIImageView on the screen, but although the syntax seems to be correct, I am getting an obscure “internal compiler error: Bus error: 10” when building. Any idea why?

-(IBAction)shakeCircle{
    int d = 3;
    [UIView animateWithDuration:0.05
    animations:^{myCircle.center = CGPointMake(myCircle.center.x+d, myCircle.center.y-d);}
    completion:^(BOOL finished){
    [UIView animateWithDuration:0.05
    animations:^{myCircle.center = CGPointMake(myCircle.center.x-d, myCircle.center.y+d);}
    completion:^(BOOL finished)
    {
        //but if I comment from here..
        [UIView animateWithDuration:0.05
        animations:^{myCircle.center = CGPointMake(myCircle.center.x+d, myCircle.center.y-d);}
        completion:^(BOOL finished){
        [UIView animateWithDuration:0.05
        animations:^{myCircle.center = CGPointMake(myCircle.center.x-d, myCircle.center.y+d);}
        ];
        }
        ];
        //... to here the code will build.

    }
    ];
    }
    ];
}

Note that if I comment out the last five lines of animation code, everything compiles fine…. What is going on?

I have tried switching to different compilers, that didn’t work. I made sure that there’s just one myCircle and that the only time it ever gets referred to is when it gets declared, and in that method!

Answer 1

Here’s a little workaround that solves the problem through recursive calls to the function. Assign to int d the amount by which to shake, then

int d = 3;
-(IBAction)shakeMyCircle{
    [UIView animateWithDuration:0.05
    animations:^{myCircle.center = CGPointMake(myCircle.center.x+3, myCircle.center.y-3);}
    completion:^(BOOL finished){
        [UIView animateWithDuration:0.05
        animations:^{myCircle.center = CGPointMake(myCircle.center.x-3, myCircle.center.y+3);}
        completion:^(BOOL finished) 
        {   
            d--;
            if(d>0) [self shakemyCircle];
            if(d == 0) d = 3;
        }
        ];
    }
    ];
}