Can any one please explain what is use of CGRectZero

问题

I am new to iOS. Can any one please explain what the use is of CGRectZero and where it is used?

回答1:

CGRectZero equals to CGRectMake(0,0,0,0). Usually it's used to fast-initialize CGRect object.

For example:

CGRect frame = CGRectZero;
frame.size.width = someWidth;
frame.size.height = someHeight;
myView.frame = frame;

From Apple's doc:

/* The "zero" rectangle -- equivalent to CGRectMake(0, 0, 0, 0). */ 

CG_EXTERN const CGRect CGRectZero
  CG_AVAILABLE_STARTING(__MAC_10_0, __IPHONE_2_0);

回答2:

CGRectZero = CGRectMake(0, 0, 0, 0);

回答3:

CGRectZero

A rectangle constant with location (0,0), and width and height of 0. The zero rectangle is equivalent to CGRectMake(0,0,0,0).

Available in OS X v10.0 and later.

Declared in CGGeometry.h.

more details Geometric Zeros

回答4:

The use of CGRectZero is to create and initialize a CGRect at (0,0,0,0)

回答5:

Swift 4.0 -

A rectangle constant with location (0,0), and width and height of 0. The zero rectangle is equivalent to CGRectMake(0,0,0,0).

CGRect.zero  == CGRect(x: 0, y: 0, width: 0, height: 0)

Doc

来源：https://stackoverflow.com/questions/22217964/can-any-one-please-explain-what-is-use-of-cgrectzero