最近项目里面要添加一个提醒更新功能，在网上查了下，代码如下：

//时间间隔一小时
    NSDate *currentDate = [NSDate date];
    NSDate *userLastOpenDate =[[NSUserDefaults standardUserDefaults] objectForKey:@"AppTimeLastOpenDate"];
    NSTimeInterval timeBetween = [currentDate timeIntervalSinceDate:userLastOpenDate];
    if ((timeBetween / 60 / 60) <= 1) {
        return;
    }else{
        [[NSUserDefaults standardUserDefaults] setObject:currentDate forKey:@"AppTimeLastOpenDate"];
        [[NSUserDefaults standardUserDefaults] synchronize];
    }

    NSString *nowVersion = [[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleVersion"];
    
    NSString *query = [NSString stringWithFormat:@"https://itunes.apple.com/lookup?id=%@", appID];
    query = [query stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
    NSData *jsonData = [[NSString stringWithContentsOfURL:[NSURL URLWithString:query] encoding:NSUTF8StringEncoding error:nil] dataUsingEncoding:NSUTF8StringEncoding];
    NSError *error = nil;
    NSDictionary *results = jsonData ? [NSJSONSerialization JSONObjectWithData:jsonData options:0 error:&error] : nil;
    
    NSArray *configData = [results valueForKey:@"results"];
    NSString *version = @"";
    for (id config in configData)
    {
        version = [config valueForKey:@"version"];
    }
    
    if ([version floatValue] > [nowVersion floatValue]) {
        UIAlertController *alertController=[UIAlertController alertControllerWithTitle:[NSString stringWithFormat:@"新版本%@已发布",version] message:nil preferredStyle:UIAlertControllerStyleAlert];
        UIAlertAction *action=[UIAlertAction actionWithTitle:@"更新" style:UIAlertActionStyleDestructive handler:^(UIAlertAction * _Nonnull action){
            
            [[UIApplication sharedApplication] openURL:[NSURL URLWithString:[NSString stringWithFormat:@"https://itunes.apple.com/us/app/chuang-youapp/id%@?mt=8",appID]]];
        }];
        UIAlertAction *cancel = [UIAlertAction actionWithTitle:@"取消" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action){
            
        }];
        [alertController addAction:action];
        [alertController addAction:cancel];
        [self presentViewController:alertController animated:YES completion:nil];
    }

整体思路就是：
1、拿当前版本的版本号跟AppStore上的版本号去比较，如果当前版本比AppStore上的要低，说明有新版本已经更新，弹出提醒框；
2、用户点击更新，通过URL跳转到AppStore上去更新；
3、为了更好的体验效果添加一个时间间隔，不会在用户每次使用的时候都会提示有更新。