函数respondsToSelector的使用

-(BOOL)respondsToSelector: selector //用来判断是否有以某个名字命名的方法（被封装在一个selector的对象里传递）

@protocol appViewDelegate <NSObject>
	@optional
	- (void) theButtonOnClicked:(UIButton *)button;
@end

if([self.delegate respondsToSelector:@selector(theButtonOnClicked:)]) {
	self.delegate theButtonOnClicked:sender;
}

#pragma mark - appViewDelegate

- (void) theButtonOnClicked:(UIButton *)button {
	button.enabled = NO;
	[]button setTitle:@"已下载" ForState:UIControlStateDisabled];
}