iOS-禁用TextField的粘贴、拷贝等功能

自定义一个继承于UITextField的TextField, 并重载它的方法

// 覆盖系统方法, 关闭 - 粘贴 剪切 选择 复制等Menu- (BOOL)canPerformAction:(SEL)action withSender:(id)sender {    [UIMenuController sharedMenuController].menuVisible = NO;    if (action == @selector(copy:)) {        return NO;    } else if (action == @selector(selectAll:)) {        return NO;    }        return NO;}