Question

I tried to move CALayer with touch event. But there are error messages.

- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
    // get touched point
    CGPoint pt = [[touches anyObject] locationInView:self];
    [self.layer convertPoint:pt toLayer:self.layer.superlayer];

    // move piece to the point
    piece.bounds.origin = pt; <- "Expression is not assignable" 
    }
}

I have look for solution of this problem, and reached to that this is problem of strucnt of Objective-C object. But I couldn’t get the solution.

Thanks for your kindness.

Answer 1

Yeah, it’s not assignable. The same goes for UIViews and it’s subclasses.

We can’t set a CALayer.bounds.origin or CALayer.bounds.size properties. What we can do, is create a CGRect and assign it to CALayer.bounds or CALayer.frame.

So, something like:

// Use frame, not bounds:
piece.frame = CGRectMake(pt.x, pt.y, piece.frame.size.width, piece.frame.size.height); <- "Expression is assignable"