在Mac上无法通过ARC使用responsToSelector

问题描述

在ARC环境中调用respondsToSelector时，出现以下错误消息Automatic Reference Counting Issue No known instance method for selector respondsToSelector:

When I call respondsToSelector in an ARC environment, I get the following error message Automatic Reference Counting Issue No known instance method for selector respondsToSelector:

这是标题

#import <AppKit/AppKit.h>


@class MTScrollView;

@protocol MTScrollViewDelegate
-(void)scrollViewDidScroll:(MTScrollView *)scrollView;
@end


@interface MTScrollView : NSScrollView
{

}

@property(nonatomic, weak) id<MTScrollViewDelegate>delegate;

@end

这是实现文件

#import "MTScrollView.h"

@implementation MTScrollView

@synthesize delegate;


- (void)reflectScrolledClipView:(NSClipView *)aClipView
{
    [super reflectScrolledClipView:aClipView];

    if([delegate respondsToSelector:@selector(scrollViewDidScroll:)])
    {
        [delegate scrollViewDidScroll:self];
    }
}

@end

关于为什么会出现此错误的任何建议?

Any suggestions on why I am getting this error?

推荐答案

使协议符合NSObject

Make the protocol conform to NSObject

@protocol MTScrollViewDelegate <NSObject>

否则，编译器认为该对象不会响应respondsToSelector之类的NSObject消息，并且会生成警告.它将在运行时成功，而不会出现任何问题.

Otherwise the compiler doesn't think that the object will respond to NSObject messages like respondsToSelector, and will generate a warning. It will succeed at runtime without issues either way.

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