如何向 appstore 查询已发布 APP 的信息？

如果我们需要实现版本的 app 自动更新，那么我们需要获取当前运行程序的版本信息和 appstore 里发布的最新版本信息。

当前运行程序的版本信息，可以在 mainBundle 里面获取：

 NSDictionary *infoDict = [[NSBundle mainBundle] infoDictionary];
     NSString *currentVersion = [infoDict objectForKey:@"CFBundleVersion"];

而 appstore 里发布的最新版本信息获取稍微复杂一些，有两种方案，思路都是一样的：

其一：在某个服务器上存储最新发布的版本信息，需要的时候向该服务器查询；

其二：在需要的时候向 appstore 查询；

在这里我来介绍第二种方法：向 appstore 查询应用程序信息，包括作者，版本，app 介绍页面地址等信息。

英文好的同学可以参考 apple 的文档：www.apple.com/itunes/affiliates/resources/documentation/itunes-store-web-service-search-api.html

具体步骤如下：

1，用 POST 方式发送请求：

http://itunes.apple.com/search?term=你的应用程序名称&entity=software

更加精准的做法是根据 app 的 id 来查找：

http://itunes.apple.com/lookup?id=你的应用程序的ID

2，从获得的 response 数据中解析需要的数据。因为从 appstore 查询得到的信息是 JSON 格式的，所以需要经过解析。解析之后得到的原始数据就是如下这个样子的：

 {
     resultCount = 1;
     results =     (
                 {
             artistId = 301724683;
             artistName = Citibank;
             artistViewUrl = "http://itunes.apple.com/us/artist/citibank/id301724683?uo=4";
             artworkUrl100 = "http://a5.mzstatic.com/us/r1000/117/Purple/a1/85/a9/mzl.hvwnfdkw.png";
             artworkUrl512 = "http://a5.mzstatic.com/us/r1000/117/Purple/a1/85/a9/mzl.hvwnfdkw.png";
             artworkUrl60 = "http://a2.mzstatic.com/us/r1000/099/Purple/67/86/7e/mzi.utfdvrgy.png";
             averageUserRating = "3.5";
             averageUserRatingForCurrentVersion = 5;
             contentAdvisoryRating = "4+";
             currency = USD;
             description = "Description of you app.";
             features =             (
                 iosUniversal
             );
             fileSizeBytes = 4141195;
             genreIds =             (
                 6015
             );
             genres =             (
                 Finance
             );
             ipadScreenshotUrls =             (
                 "http://a1.mzstatic.com/us/r1000/095/Purple/e0/a6/17/mzl.pbbxcjzt.1024x1024-65.jpg",
                 "http://a3.mzstatic.com/us/r1000/036/Purple/cc/14/98/mzl.dyairego.1024x1024-65.jpg"
             );
             isGameCenterEnabled = 0;
             kind = software;
             languageCodesISO2A =             (
                 EN
             );
             price = 0;
             primaryGenreId = 6015;
             primaryGenreName = Finance;
             releaseDate = "2011-01-24T06:14:35Z";
             releaseNotes = "* View Real-time streaming prices for U.S. Treasuries \n\n* Open and Save your Citi Research in your favorite PDF Reader and Library such as iBooks\n\n* Search for your favorite videos";
             screenshotUrls =             (
                 "http://a3.mzstatic.com/us/r1000/066/Purple/17/51/fb/mzl.zywiavgn.png",
                 "http://a5.mzstatic.com/us/r1000/026/Purple/73/85/97/mzl.csmdtndk.png"
             );
             sellerName = "Citibank, N.A.";
             sellerUrl = "http://";
             supportedDevices =             (
                 all
             );
             trackCensoredName = "Citi Velocity";
             trackContentRating = "4+";
             trackId = 414697122;
             trackName = "Citi Velocity";
             trackViewUrl = "http://itunes.apple.com/us/app/citi-velocity/id414697122?mt=8&uo=4";
             userRatingCount = 5;
             userRatingCountForCurrentVersion = 1;
             version = "1.4";
             wrapperType = software;
         }
     );
 }

然后从中取得 results 数组即可，具体代码如下所示：

 NSDictionary *jsonData = [dataPayload JSONValue];
 NSArray *infoArray = [jsonData objectForKey:@"results"];
 NSDictionary *releaseInfo = [infoArray objectAtIndex:0];
 NSString *latestVersion = [releaseInfo objectForKey:@"version"];
 NSString *trackViewUrl = [releaseInfo objectForKey:@"trackViewUrl"];

如果你拷贝 trackViewUrl 的实际地址，然后在浏览器中打开，就会打开你的应用程序在 appstore 中的介绍页面。当然我们也可以在代码中调用 safari 来打开它。

 UIApplication *application = [UIApplication sharedApplication];
 [application openURL:[NSURL URLWithString:trackViewUrl]];