如何整理嵌套回调

我正在使用Unity的FB SDK，我发现由于异步函数需要按顺序返回而丢失回调，这很麻烦。我如何抽象我的代码，所以这是更干净，从异步回调分离我的逻辑/流?

我的逻辑是:

• 如果玩家没有登录，登录他们(异步)
• 如果他们登录，然后检查他们有正确的权限(Async)
• 如果他们没有正确的权限，请求他们。(异步)
• 一旦他们有"发布分数"的权限，发布分数。(异步)

下面是我想做的一个伪例子:

Init()
{
 LogInWithCallback(LoginResponse);
}
public LoginResponse(response)
{
   if(response.loggedIn)
   {
      checkPermissions();
   }
}
public checkPermissions(){
   checkPermissionsWithCallback(permissionCheckCallback);
}
public permissionCheckCallback(ResponseDelegate)
{
  //If the player doesn't have the right permissions, request them.
   requestPermissions("score permission",permissionRequestCallback);
 }
 public permissionRequestCallback()
 {
   //if requesting the score permission was successful post score;
   Postscore();  // <- It doesn't make sense to have logic which posts the player's score this deep down a callback chain, but I don't know any other way around.
 }