objective c - iOS frame change one property (eg width)

Question

This question was originally asked for the objective-c programming language. At the time of writing, swift didn't even exist yet.

Question

Is it possible to change only one property of a CGRect ?

For example:

self.frame.size.width = 50;

instead of

self.frame = CGRectMake(self.frame.origin.x, 
                        self.frame.origin.y, 
                        self.frame.size.width, 
                        50);

of course I understand that self.frame.size.width is read only so I'm wondering how to do this?

CSS ANALOGY proceed at your own risk

for those of you who are familiar with CSS, the idea is very similar to using:

margin-left: 2px;

instead of having to change the whole value:

margin: 5px 5px 5px 2px;

Answer 1

To answer your original question: yes, it's possible to change just one member of a CGRect structure. This code throws no errors:

myRect.size.width = 50;

What is not possible, however, is to change a single member of a CGRect that is itself a property of another object. In that very common case, you would have to use a temporary local variable:

CGRect frameRect = self.frame;
frameRect.size.width = 50;
self.frame = frameRect;

The reason for this is that using the property accessor self.frame = ... is equivalent to [self setFrame:...] and this accessor always expects an entire CGRect. Mixing C-style struct access with Objective-C property dot notation does not work well in this case.