OC实战: 抽象类的实现

来源：互联网发布：性价比实木家具知乎编辑：程序博客网时间：2024/04/30 14:06

这里, 假设你已经明白了

* oc 的继承.

* oc 的多态.其实 oc 里面的方法都是虚方法.

* oc 的协议 protocol.

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在多人协助的项目开发中, 一般在设计框架的时候, 我们会约定一些协议, 这些协议是必须要在子类里面实现的.

但是, 有些队友会忘记去实现, 导致一些莫名其妙的问题.

那么, 如果我们能实现类似 c++ 或者 java 的抽象类, 就在一定程度上可以避免这种问题的发生.

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今天. 主要跟大家分享一下, 实现抽象类的思路.~

DownloaderProtocol.h 协议

#import <Foundation/Foundation.h>@protocol DownloaderProtocol <NSObject>@required- (BOOL)checkDownloader;- (void)startDownload:(id)url;- (void)stopDownload;- (void)deleteAllDownloadFile;@end

AbstractDownloader.h

#import <Foundation/Foundation.h>#import "DownloaderProtocol.h"@interface AbstractDownloader : NSObject <DownloaderProtocol>- (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];}- (BOOL)checkDownloader{    AbstractMethodNotImplemented();}- (void)startDownload:(id)url{    AbstractMethodNotImplemented();}- (void)stopDownload{    AbstractMethodNotImplemented();}- (void)deleteAllDownloadFile{    AbstractMethodNotImplemented();}- (void)setDownloadUrl:(NSString *)url{    NSLog(@"AbstractDownloader's url = %@", url);}@end

看一下具体实现类.

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

完成了继承抽象类并实现其方法的条件.

使用

    ImageDownloader *downloader = [[ImageDownloader alloc] init];    [downloader setDownloadUrl:@"url://www.url.com.cn.ht"];    [downloader checkDownloader];    [downloader startDownload:nil];    [downloader stopDownload];    [downloader deleteAllDownloadFile];

Have fun...

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