如何判断ios设备中是否安装了某款应用

URL Schemes关键字研究一下即可 常见得URL Schemes见http://www.cnblogs.com/huangzs/p/4491286.html   

    if ([[UIApplication sharedApplication] canOpenURL:[NSURL URLWithString:@"alipay://"]])

    {

        NSLog(@" installed");

        NSURL *url = [NSURL URLWithString:@"alipay://"];

        [[UIApplication sharedApplication] openURL:url];

    }

    else

    {

        //提示用户去下载

        UIAlertView *alert=[[UIAlertView alloc]initWithTitle:@"提示" message:@"支付宝未安装,是否去下载最新版本的支付宝?" delegate:self cancelButtonTitle:@"取消" otherButtonTitles:@"下载",nil];

        alert.tag=8789;

        [alert show];

    }

//警报0取消1下载

- (void)alertView:(UIAlertView *)alertView clickedButtonAtIndex:(NSInteger)buttonIndex

{

    if (alertView.tag==8789) {

        if (buttonIndex==0) {

            return;

        } else  if (buttonIndex==1){

            NSURL *url = [NSURL URLWithString:@"https://itunes.apple.com/cn/app/zhi-fu-bao-qian-bao-qiang/id333206289?mt=8"];

            [[UIApplication sharedApplication] openURL:url];

        }

    }

    

}