网络内容消费：URL缩短、JSON解析与异步处理

### 网络内容消费：URL 缩短、JSON 解析与异步处理 #### 1. URL 缩短功能实现 URL 缩短功能可以将长 URL 转换为短 URL，方便分享和使用。以下是实现该功能的详细步骤和代码： - **定义 `LinkShortener` 类**： ```objective-c // LinkShortener.h #import <Foundation/Foundation.h> @interface LinkShortener : NSObject<NSXMLParserDelegate> { @private NSMutableString *recorderString; NSString *currentElement; } - (NSString *)getTheShortURLVersionOfThisLongURL:(NSString *)longURL; @end ``` - **实现 `LinkShortener` 类的方法**： ```objective-c // LinkShortener.m #import "LinkShortener.h" @implementation LinkShortener - (NSString *)getTheShortURLVersionOfThisLongURL:(NSString *)longURL { #warning Get your API Login from https://bitly.com/ and put it here before running NSString *APILogin = @"[YOUR API LOGIN]"; #warning Get your API key from https://bitly.com/ and put it here before running NSString *APIKey = @"[YOUR API KEY]"; NSString *requestString = [[NSString alloc] initWithFormat: @"http://api.bit.ly/shorten?version=2.0.1" @"&longUrl=%@&login=%@&apiKey=%@&format=xml", longURL, APILogin, APIKey]; NSURL *requestURL = [NSURL URLWithString:requestString]; recorderString = nil; NSData *responseData = [NSData dataWithContentsOfURL:requestURL]; NSXMLParser *xmlParser = [[NSXMLParser alloc] initWithData:responseData]; xmlParser.delegate = self; [xmlParser parse]; if (recorderString) return [recorderString copy]; else return nil; } - (void)parser:(NSXMLParser *)parser didStartElement:(NSString *)elementName namespaceURI:(NSString *)namespaceURI qualifiedName:(NSString *)qName attributes:(NSDictionary *)attributeDict { currentElement = [elementName copy]; if ([elementName isEqualToString:@"shortUrl"]) { recorderString = [[NSMutableString alloc] init]; } } - (void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string { if ([currentElement isEqualToString:@"shortUrl"]) [recorderString appendString:string]; } @end ``` - **在 `main.m` 中使用 `LinkShortener` 类**： ```objective-c // main.m #import <Foundation/Foundation.h> #import "LinkShortener.h" int main(int argc, const char * argv[]) { @autoreleasepool { NSString *longURL = @"http://howtomakeiphoneapps.com/" "how-to-asynchronously-add-web-content-to-uitableview-in-ios/1732/"; LinkShortener *linkShortener = [[LinkShortener alloc] init]; NSString *shortURL = [linkShortener getTheShortURLVersionOfThisLongURL:longURL]; NSLog(@"shortURL = %@", shortURL); } return 0; } ``` - **使用步骤**： 1. 从 `https://bitly.com/` 获取 API 登录名和 API 密钥，并替换代码中的 `[YOUR API LOGIN]` 和 `[YOUR API KEY]`。 2. 将 `LinkShortener.h` 头文件导入到需要使用该功能的类中。 3. 实例化 `LinkShortener` 对象。 4. 调用 `getTheShortURLVersionOfThisLongURL:` 方法，传入长 URL 作为参数，获取短 URL。 #### 2. 使用 JSON 消费 Web 服务 JSON 是一种用于数据存储和传输的格式，许多互联网公司在实现 Web 服务时会使用它。以下是使用 JSON 消费 Web 服务的详细步骤和代码： - **构造请求字符串**： ```objective-c NSString *longURL = @"http://howtomakeiphoneapps.com/" "how-to-asynchronously-add-web-content-to-uitableview-in-ios/1732/"; #warning Get your API Login from https://bitly.com/ and put it here before running NSString *APILogin = @"[YOUR API LOGIN]"; #warning Get your API key from https://bitly.com/ and put it here before running NSString *APIKey = @"[YOUR API KEY]"; NSString *requestString = [[NSString alloc] initWithFormat: @"http://api.bit.ly/shorten?version=2.0.1" @"&longUrl=%@&login=%@&apiKey=%@&format=json", longURL, APILogin, APIKey]; ``` - **获取响应数据**： ```objective-c NSURL *requestURL = [NSURL URLWithString:requestString]; NSData *responseData = [NSData dataWithContentsOfURL:requestURL]; ``` - **解析 JSON 数据**： ```objective-c NSError *error = nil; NSDictionary *bitlyJSON = [NSJSONSerialization JSONObjectWithData:responseData options:0 error:&error]; if (!error) { NSDictionary *results = [bitlyJSON objectForKey:@"results"]; NSDictionary *resultsForLongURL = [results objectForKey:longURL]; NSString *shortURL = [resultsForLongURL objectForKey:@"shortUrl"]; NSLog(@"shortURL = %@", shortURL); } else { NSLog(@"There was an error parsing the JSON"); } ```