Objective-C抽象类的实现_objective c实现抽象类-优快云博客

本文链接：https://blog.youkuaiyun.com/James15902085063/article/details/79497151

这篇博客探讨了如何在Objective-C中使用抽象类来实现下载功能。通过定义一个DownloaderProtocol协议，创建抽象类AbstractDownloader，以及具体的实现类如ImageDownloader，详细阐述了抽象类在接口设计和实现过程中的应用。

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以下载功能为例:

1.协议
DownloaderProtocol.h

    #import <Foundation/Foundation.h>  

    @protocol DownloaderProtocol <NSObject>  
    @required    
    - (BOOL)checkDownloader;  
    - (void)startDownload:(id)url;  
    - (void)stopDownload;  
    - (void)deleteAllDownloadFile;

    //可以使用@optional定义"可选的"接口
    //略

    @end

2.抽象类
AbstractDownloader.h

    #import <Foundation/Foundation.h>  
    #import "DownloaderProtocol.h"  

    //遵循协议!!  
    @interface AbstractDownloader : NSObject <DownloaderProtocol>  

    //自己的方法  
    - (void)setDownloadUrl:(NSString *)url;  
    @end

AbstractDownloader.m

#import "AbstractDownloader.h"  

#define AbstractMethodNotImplemented() \  
@throw [NSException exceptionWithName:NSInternalInconsistencyException \  
reason:[NSString stringWithFormat:@"You must override %@ in a subclass.", NSStringFromSelector(_cmd)] \  
userInfo:nil]  


@implementation AbstractDownloader  
- (instancetype)init  
{  
    NSAssert(![self isMemberOfClass:[AbstractDownloader class]], @"AbstractDownloader is an abstract class, you should not instantiate it directly.");  

    return [super init];  
}  

//让子类自己去实现  如果没有实现则此处抛出异常
- (BOOL)checkDownloader  
{  
    AbstractMethodNotImplemented();  
}  

- (void)startDownload:(id)url  
{  
    AbstractMethodNotImplemented();  
}  

- (void)stopDownload  
{  
    AbstractMethodNotImplemented();  
}  

- (void)deleteAllDownloadFile  
{  
    AbstractMethodNotImplemented();  
}  

  //自己的方法
- (void)setDownloadUrl:(NSString *)url  
{  
    NSLog(@"AbstractDownloader's url = %@", url);  
}

3.具体实现类

ImageDownloader.h

    #import "AbstractDownloader.h"  

    @interface ImageDownloader : AbstractDownloader  

    @end

ImageDownloader.m

    #import "ImageDownloader.h"  

    @implementation ImageDownloader  

    - (BOOL)checkDownloader  
    {  
        NSLog(@"ImageDownloader checkDownloader...");  

        return YES;  
    }  

    - (void)startDownload:(id)url  
    {  
        NSLog(@"ImageDownloader startDownload...");  
    }  

    - (void)stopDownload  
    {  
        NSLog(@"ImageDownloader stopDownload...");  
    }  

    - (void)deleteAllDownloadFile  
    {  
        NSLog(@"ImageDownloader deleteAllDownloadFile...");  
    }  

    @end