Question

Quite often, I’ll want to move an object along by 2 points, so I’ll put:

CGRectMake(currentobject.frame.origin.x+2, currentObject.frame.origin.y, currentObject.frame.size.width, currentObject.frame.size.height);

Is there a quicker way, where either I can just change the 1 thing, or where I can quickly reference the current values?

Answer 1

You should use CGRectOffset():

NSAssert(currentObject, @"%s: Must have |currentObject|.", __func__);
CGRect offsetFrame = CGRectOffset([currentObject frame], 2/*dx*/, 0/*dy*/);
[currentObject setFrame:offsetFrame];

Note the assertion: a method with a struct return value is one of the few cases where sending a message to nil can return junk rather than some equivalent to zero (0, 0.0, nil, Nil, &c.).

The equivalent of CGRectOffset() for growing or shrinking the frame (changing the size) is CGRectInset().

An alternative to using CGRectOffset() when working with UIView is to just displace the view’s center:

view.center.x += 2;

This updates the frame accordingly.