2019-04-10 runtime之修改UITextField

项目需求：UITextField和UITextView长按文字只能出现选择、全选、拷贝、粘贴选项
用runtime实现，给UITextField和UITextView写个分类，重写load方法，替换系统canPerformAction:withSender:方法

@implementation UITextField (zxh)
+(void)load{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        Method m1 = class_getInstanceMethod(self, NSSelectorFromString(@"zxh_canPerformAction:withSender:"));
        Method m2 = class_getInstanceMethod(self, NSSelectorFromString(@"canPerformAction:withSender:"));
        method_exchangeImplementations(m1, m2);
    });

}

-(BOOL)zxh_canPerformAction:(SEL)action withSender:(id)sender{
    if (action == @selector(select:))
    {
        return YES;
    }
    else if (action == @selector(selectAll:))
    {
        return YES;
    }

    else if (action == @selector(copy:))
    {
        return YES;
    }
    else if (action == @selector(paste:))
    {
        return YES;
    }
    else{
        return NO;
    }
}
@end

@implementation UITextView (zxh)

+(void)load{
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        Method m1 = class_getInstanceMethod(self, NSSelectorFromString(@"zxh_canPerformAction:withSender:"));
        Method m2 = class_getInstanceMethod(self, NSSelectorFromString(@"canPerformAction:withSender:"));
        method_exchangeImplementations(m1, m2);
    });

}

-(BOOL)zxh_canPerformAction:(SEL)action withSender:(id)sender{
        if (action == @selector(select:))
        {
            return YES;
        }
        else if (action == @selector(selectAll:))
        {
            return YES;
        }

        else if (action == @selector(copy:))
        {
            return YES;
        }
        else if (action == @selector(paste:))
        {
            return YES;
        }
        else{
            return NO;
        }
}
@end