objective-c – 进行消息转发时避免编译器警告

我创建了一个包装UITextView并添加一些ui元素的类.我希望新类’API与UITextView相同,因此我使用消息转发(下面列出)在包装文本视图和委托之间中继消息.

令人恼火的是,编译器会在转发类的实例上发出方法调用警告.例如,将为以下行生成错误：

[aMyTextView setContentOffset:CGPointZero animated:YES];

所以我被迫为这些方法声明并创建“手动转发”实现,这违背了使用消息转发的整个目的.

- (void)setContentOffset:(CGPoint)contentOffset animated:(BOOL)animated
{
    [_textView setContentOffset:contentOffset animated:animated];
}

我知道解决这个问题的通常方法是使用performSelector：方法之一,但这是一个麻烦的,当一些参数不是NSObjects时(虽然Erica Sadun’s extensions是一个很大的帮助),b)再次,完全违背了创建一个透明的包装器.

(子类化UITextView也是不可能的,因为我需要在文本视图下面插入视图.)

有办法解决这个问题吗？

列出该类的所有相关部分：

@interface MyTextField : UIView<UITextViewDelegate>
{
    UIImageView*                        _border;
    UITextView*                         _textView;
    UIButton*                           _clearButton;
    NSObject<UITextViewDelegate>*       _delegate;
}

@implementation MWTextField
. . . 
// Forwards messages in both directions (textView <--> delegate)
#pragma mark Message forwarding

// Protocol messages will only be sent if respondsToSelector: returns YES
- (BOOL)respondsToSelector:(SEL)aSelector
{
    if ([_delegate respondsToSelector:aSelector])
        return YES;
    else
        return [super respondsToSelector:aSelector];
}

- (NSMethodSignature *)methodSignatureForSelector:(SEL)selector
{
    // First,try to find it in the UITextView
    if ([_textView respondsToSelector:selector])
    {
        return [_textView methodSignatureForSelector:selector];
    }
    // Then try the delegate
    else if ([_delegate respondsToSelector:selector])
    {
        return [_delegate methodSignatureForSelector:selector];
    }
    else
    {
        return [super methodSignatureForSelector: selector];
    }
}

- (void)forwardInvocation:(NSInvocation *)invocation
{
    SEL aSelector = [invocation selector];

    if ([_textView respondsToSelector:aSelector])
    {
        [invocation invokeWithTarget:_textView];
    }
    else if ([_delegate respondsToSelector:aSelector])
    {
        [invocation invokeWithTarget:_delegate];
    }
    else
    {
        [self doesNotRecognizeSelector:aSelector];
    }
}
. . .
@end

解决方法

声明一个类别,该类别提供您要转发的方法的方法声明：

@interface MyTextField (ImGonnaLetYouFinishButFirstImForwardingThese)
... methods you want to forward here ...
@end

无需提供@implementation.

请注意,这是一种相当不典型的模式.不公平,非常.应该没有理由不能进行子类化.你说Subclassing UITextView也是不可能的,因为我需要在文本视图下面插入视图,但事实并非如此.

If I subclass UITextField,all I can
do with the other views is to add them
as subviews,which means they will be
on top of the text field. I guess I
could modify drawRect:… Is that what
you would suggest? Or what do you have
up your sleeve there?

如果需要组,请创建一个UIView子类,该子类适当地管理各种子视图,不需要转发.然后你可以随意订购视图.

很少使用转发.沿着这条路走下去就是疯狂.这听起来好像你的设计有点杂草,但没有足够的信息来真正说出更具体的信息.