摘要：
for(UIView*viewin[self.backgroundViewsubviews]){//[viewremovefromsuperview];if([[[viewsuperclass]description]isEqualToString:@"UIButton"]){UIButton*btn=(UIButton*)view;btn.titleLabel.text=@"dynamictitle";btn.center=btn.superview.center;}}-(IBAction)addButton:(id)sender{CGRectfram 阅读全文
摘要：
20.5.2 Infinity and NaNIEEE754floating point numbers can represent positive or negative infinity, andNaN(not a number). These three values arise from calculations whose result is undefined or cannot be represented accurately. You can also deliberately set a floating-point variable to any of them, wh 阅读全文