指派的另一種寫法

Ever since I found out that a GCC C extension causes a code block to return a value if you enclose it in round brackets, I’ve been using it in my code. What do you think?

self.bounds = ({
	CGRect bounds = self.bounds;
	bounds.size.height = self.currentYPosition + SHEETINSETY;
	bounds;
});
      

I’m also using this for frame. The advantage is that with this construct I never forget to set the frame after altering it, which I did far too often otherwise.

self.helpButton = ({	// helpbutton
  UIButton *button = [UIButton buttonWithType:UIButtonTypeCustom];
  [button setImage:[UIImage imageNamed:@"ParentalControlQuestionMarkButton"] forState:UIControlStateNormal];
  CGRect buttonRect = innerBounds;
  buttonRect.size = [button sizeThatFits:CGSizeMake(400, 400)];
  buttonRect.origin.x = CGRectGetMaxX(innerBounds)-CGRectGetWidth(buttonRect);
  button.frame = UIEdgeInsetsInsetRect(buttonRect, UIEdgeInsetsMake(0, -10, -20, -10));
  [button addTarget:self action:@selector(helpAction:) forControlEvents:UIControlEventTouchUpInside];
  [self addSubview:button];
  button;
});
      

The major benefits of this one are:

• the instance variable in which I will store the generated object is in the first line, clearly showing what the next part of the code does. Prior to this, the assignment happend at the end.
• the stack variables declared and used don’t pollute other code in the same function/method. I can feel free to use very generic names (view,frame,rect,button) and not get into conflict with other parts.

Update: And it all works with CLANG due to the great design policy of CLANG to support most of the GCC extensions to maximise compatibility.