Question

我必须有两个类，它们提供了检测每个类的类所需的不同函数，然后执行那些导致代码重复的函数。有没有办法指定id？

@property (nonatomic, retain) id player;
    -(void) checkPlayer
    {
        if ([self.player isKindOfClass:[MPMoviePlayerController class]]){
            MPMoviePlayerController* player = (MPMoviePlayerController*) self.player;
            if (player.loadState != MPMovieLoadStateStalled || player.loadState != MPMovieLoadStateStalled)
            {
               // do something
            }
        }
        else if([self.player isKindOfClass:[MyCustomPlayerController class]]) {
            MyCustomController* player = (MyCustomPlayerController*) self.player;
            if (player.loadState != MPMovieLoadStateStalled || player.loadState != MPMovieLoadStateStalled)
            {
               // do something else
            }
        }
    }

Answer 1

最好在这种情况下使用协议。你的代码会很干净。

示例：

@protocol Player
- (StateEnum)state;
@end

@interface MyCustomPlayerController <Player>
@end

@interface MPMoviePlayerController <Player>
@end


@property (nonatomic, retain) id<Player> player;
-(void) checkPlayer {
   if (self.player.state != MPMovieLoadStateStalled || self.player.state != MPMovieLoadStateStalled)
   }
}

Answer 2

您可以通过创建@protocol

来消除代码重复

@protocol LoadStateProtocol <NSObject>

@property (assign, ...) MPMovieLoadState loadState; 

@end

并且MyCustomPlayerController和MPMoviePlayerController都符合此协议。

@interface MyCustomPlayerController < LoadStateProtocol >
/* ... */
@end

如果MPMoviePlayerController不是您的类BUT之一已经具有属性loadState，只需在.m文件中创建一个objC类别，该文件具有checkPlayer方法

@interface MPMoviePlayerController (LoadStateProtocol) 
< LoadStateProtocol >
@end
@implementation MPMoviePlayerController (LoadStateProtocol)
@end

然后你可以停止检查：只需将self.player的类型更改为id< LoadStateProtocol >

即可

检查id类类型，无需重复代码

2 个答案: