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]];