禁用UITextField复制粘贴等方法

1 - (BOOL)canPerformAction:(SEL)action withSender:(id)sender{
2     if (action == @selector(paste:)  ||     //粘贴
3         action == @selector(select:) ||     //复制
4         action == @selector(selectAll:))    //全选
5     {
6         return NO;
7     }
8     return [super canPerformAction:action withSender:sender];
9 }