Difference between frame.size.width and frame.width

Question

I was writing a program in swift and just now I noticed that I can directly access a CGRect frame\'s width and height properties directly without using the

Answer 1

In Objective C, when I tried to write the same code, the line height = view.frame.height is throwing an error. Can anyone please tell me the difference (if any) in these two lines of code.

CGGeometry.h defines a couple of types, among them the C struct CGRect. This struct has two members: origin and size.

That's all you can access in C (and Objective-C) using dot notation. Neither C nor Objective-C offer extensions for structs.

Swift imports the type as a Swift struct. The difference is that Swift does allow for extensions on structs. So it exposes several free C functions as extensions:

CGRectGetMinX() — CGRect.minX
CGRectGetMidX() — CGRect.midX
CGRectGetMaxX() — CGRect.maxX
CGRectGetWidth() — CGRect.width
[... same for y]

These C functions are there since ages—they just live in a dusty corner of CoreGraphics.

They are quite useful but you have to know their semantics (which differ a bit from the standard accessors): They normalise the dimensions.

This means that they convert a rect with negative width or height to a rect that covers the same area with positive size and offset origin.

let rect = CGRect(x: 0, y: 0, width: 10, height: -10)
assert(rect.width == rect.size.width)   // OK
assert(rect.height == rect.size.height) // boom