iOS AppStore版本升级详解

虽然App Store能够提醒用户软件更新，但很多用户不会主动去更新一大堆的软件（我机器上待更新的软件在100个左右）。如果在软件开启时提醒用户更新 或者 更多中设置“检查更新”项，效果会好很多。
　　通常的做法是在自己的服务器上记录最新版本号，从iOS客户端请求，与本地版本号比较，不同则提示更新。这种做法简单，缺点是需要单独的服务器支持。

　　通过查阅相关文章，找到了如下方法，与上述方法类似，不过不需要另外的服务器支持。此为检查更新的最优方法。

NSString *version = @"";
NSURL *url = [NSURL URLWithString:@"http://itunes.apple.com/lookup?id=954270"];
versionRequest = [ASIFormDataRequest requestWithURL:url];
[versionRequest setRequestMethod:@"GET"];
[versionRequest setDelegate:self];
[versionRequest setTimeOutSeconds:150];
[versionRequest addRequestHeader:@"Content-Type" value:@"application/json"]; 
[versionRequest startSynchronous];

//Response string of our REST call
NSString* jsonResponseString = [versionRequest responseString];
NSDictionary *loginAuthenticationResponse = [jsonResponseString objectFromJSONString];
NSArray *configData = [loginAuthenticationResponse valueForKey:@"results"];
for (id config in configData) 
{
  version = [config valueForKey:@"version"];
}
//Check your version with the version in app store
if (![version isEqualToString:[itsUserDefaults objectForKey:@"version"]]) 
{
   ProAlertView *createUserResponseAlert = [[ProAlertView alloc] initWithTitle:@"New Version!!" message: @"A new version of app is available to download" delegate:self cancelButtonTitle:@"Cancel" otherButtonTitles: @"Download", nil];
   [createUserResponseAlert show]; 
   [createUserResponseAlert release];
}

- (void)alertView:(UIAlertView *)actionSheet clickedButtonAtIndex:(NSInteger)buttonIndex {
    // the user clicked one of the OK/Cancel buttons
    if (buttonIndex == 1)
    {
        NSString *iTunesLink = @"itms-apps://phobos.apple.com/WebObjects/MZStore.woa/wa/viewSoftwareUpdate?id=<appid>&mt=8";
        [[UIApplication sharedApplication] openURL:[NSURL URLWithString:iTunesLink]];
    }
}

请求http://itunes.apple.com/lookup?id=954270返回的数据给出的version为2.3, 与本地客户端版本号比较，即可判断有无更新。