scope variable undefined outside `.then` method

问题:

I changed the scope variable in an if statement and outside the if statement it turned into an undefined variable

app.controller("Login", function($scope, $window,$http){
    var status;
    $scope.loginUser = function(logData){
        $http.post('/corporate/login',logData).then(function(response){
              var data = response.data
              var status = data.success;
              if(status == true){
                $scope.logStatus = true;
                console.log($scope.logStatus); // prints true
              }else{
                $scope.logStatus = false;
              }
        })

        console.log($scope.logStatus); //prints undefined
    }
});

回答1:

outside ... it turned into an undefined variable

It did not "turn into" an undefined value. The last console.log in the code executes before the console.log in the success handler. It is undefined because it has not yet been set by the success handler.

---

Expaination of Promise-Based Asynchronous Operations

console.log("Part1");
console.log("Part2");
var promise = $http.get(url);
promise.then(function successHandler(response){
    console.log("Part3");
});
console.log("Part4");

The console log for "Part4" doesn't have to wait for the data to come back from the server. It executes immediately after the XHR starts. The console log for "Part3" is inside a success handler function that is held by the $q service and invoked after data has arrived from the server and the XHR completes.

For more information, see How to use $http promise response outside success handler.

Demo

console.log("Part 1");
console.log("Part 2");
var promise = new Promise(r=>r());
promise.then(function() {
    console.log("Part 3");
});
console.log("Part *4*");

回答2:

$http is asynchronous. Your if/else conditions are in the success callback. Problem is that the console.log($scope.logStatus); line is called before the success callback gets called

You should probably initialise $scope.logStatus = false before the $http call.

EDIT:

If like you said, $scope.logStatus remains false, then check if your if block is being called. See fiddle:

https://jsfiddle.net/51bsbzL0/253/