javascript - ref 内的代码一旦不执行 angularjs

Question

this.verifyUserToken block 内的代码不会执行。我猜这与异步调用有关，因为返回的数据尚未准备好，但我似乎不知道如何处理。

this.verifyUserToken = function(){
            //Check if token matches existing token and if verified is true
            ref.orderByChild('token').equalTo(this.token).once('value').
            then(function(dataSnapshot){
                //If token matches
                    if(dataSnapshot.val()){
                        alert("Token Exists",dataSnapshot.val().token);
                        $scope.isVerified = "YES";
                    }else{
                        alert("Token does not exist",dataSnapshot.val());
                        $scope.isVerified = "NO";
                    }
            });
        }

this.registerUser = function(){
            console.log("Entered registerUser()");

            this.verifyUserToken();
            alert("The Value of isVerified:"+ $scope.isVerified);
            if($scope.isVerified == "YES"){
                    alert("Verifying User Token...",this.verifyUserToken());
                    $scope.auth.$createUser({
                    "email": this.email,
                    "password" : this.password
                }).then(function(userData){
                    alert("Successfully created user account with uid:", userData.uid);
                    //redirect to /userlogin if registration is successful
                    //this.changeVerifiedStatus();
                    alert("User verifed and changed");
                    $location.path('/userlogin');
                }).catch(function(error){
                    alert("Error Creating User:",error);
                });
            }else{
                alert("Token failed verification");
            }   
            };

Answer 1

由于 verifyUserToken 有一个对 firebase 的异步调用，您可以处理它从该函数返回 Promise ，并仅在完成后继续您的 registerUser然后验证通话已完成。

我设置了 jsFiddle这样你就可以看到它的工作原理。

this.verifyUserToken = function(){
  //Check if token matches existing token and if verified is true
  var verifyUserTokenPromise = new Promise(function(resolve, reject){                                               
    ref.orderByChild('token').equalTo(this.token).once('value').then(function(dataSnapshot){
      //If token matches
          if(dataSnapshot.val()){
              alert("Token Exists",dataSnapshot.val().token);
              $scope.isVerified = "YES";
          }else{
              alert("Token does not exist",dataSnapshot.val());
              $scope.isVerified = "NO";
          }
          //resolve the promise. you can pass any data here
          resolve($scope.isVerified);
    });
  });
  return verifyUserTokenPromise;
};

this.registerUser = function(){
  console.log("Entered registerUser()");

  this.verifyUserToken().then(function(result){
    alert("The Value of isVerified:"+ $scope.isVerified);
    if($scope.isVerified == "YES"){
            alert("Verifying User Token...",this.verifyUserToken());
            $scope.auth.$createUser({
            "email": this.email,
            "password" : this.password
        }).then(function(userData){
            alert("Successfully created user account with uid:", userData.uid);
            //redirect to /userlogin if registration is successful
            //this.changeVerifiedStatus();
            alert("User verifed and changed");
            $location.path('/userlogin');
        }).catch(function(error){
            alert("Error Creating User:",error);
        });
    }else{
        alert("Token failed verification");
    }   
  })
};