步骤1

id 指的是在你的应用在苹果商店中的id号 查看方法也简单：用电脑itunes打开，搜索自己的应用，然后复制网址，网址上有就是这个id号

NSURLRequest *rep = [NSURLRequest requestWithURL:[NSURL URLWithString:@"https://itunes.apple.com/lookup?id=1160672874"]];
[NSURLConnection connectionWithRequest:rep delegate:self];

步骤2

-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{

    NSError *error;

    id jsonObject = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:&error];

    NSDictionary *appInfo = (NSDictionary*)jsonObject;

    NSArray *infoContent = [appInfo objectForKey:@"results"];

    NSString *version = [[infoContent objectAtIndex:0]objectForKey:@"version"];

    NSString *currentVersion = [[[NSBundle mainBundle] infoDictionary]objectForKey:@"CFBundleShortVersionString"];

    NSLog(@"商店的版本是%@  当前的版本是%@",version,currentVersion);

    if ([currentVersion doubleValue]<[version doubleValue]) {

        NSLog(@"new:%@ old:%@",currentVersion,version);

        UIAlertView *alerV = [[UIAlertView alloc]initWithTitle:@"发现新版本" message:@"App又添新功能啦，大量惊喜等您来发现" delegate:self cancelButtonTitle:@"知道了" otherButtonTitles:@"前往更新", nil];

        [alerV show];

    }

}