一：iOS 8 以后可以通过<code>MobileCoreService</code> 的私有 API获取 iOS 设备上安装的所有应用。（iOS11后失效）
会有审核被拒的风险，谨慎使用。

Class cls = NSClassFromString(@"LSApplicationWorkspace");
id s = [(id)cls performSelector:NSSelectorFromString(@"defaultWorkspace")];
NSArray *array = [s performSelector:NSSelectorFromString(@"allInstalledApplications")];
NSLog(@"================");
for (id item in array) {
    NSLog(@"%@",[item performSelector:NSSelectorFromString(@"applicationIdentifier")]);
    NSLog(@"%@",[item performSelector:NSSelectorFromString(@"bundleIdentifier")]);
    NSLog(@"%@",[item performSelector:NSSelectorFromString(@"bundleVersion")]);
    NSLog(@"%@",[item performSelector:NSSelectorFromString(@"shortVersionString")]);
}
NSLog(@"================");

二：利用URL schemes判断手机是否安装某app。

//判断本地是否有淘宝App
NSURL * myURL_APP_A = [NSURL URLWithString:@"taobao://"];
if ([[UIApplication sharedApplication] canOpenURL:myURL_APP_A]) {
    NSLog(@"canOpenURL");
    [[UIApplication sharedApplication] openURL:myURL_APP_A];
}
else{
    NSLog(@"淘宝未安装");
}

提醒下：iOS9需要设置白名单，大伙儿还要在plist设置。

URL schemes.png

部分URL schemes名单：https://www.zhihu.com/question/19907735