angular.js中promise多個then的問題

Question

<p ng-app="MyApp">
  <p ng-controller="MyController">
    <label for="flag">成功
      <input id="flag" type="checkbox" ng-model="flag" /><br/>
    </label>
    <p ng-cloak>
      {{status}}
    </p>
    <hr/>
    <button ng-click="handle()">点击我</button>
  </p>
</p>
<script>
  angular.module("MyApp", [])
    .controller("MyController", ["$scope", "$q", function ($scope, $q) {
      $scope.flag = true;
      $scope.handle = function () {
        var deferred = $q.defer();
        var promise = deferred.promise;

        if ($scope.flag) {
          deferred.resolve("you are lucky!");
        } else {
          deferred.reject("sorry, it lost!");
        }
        promise.then(function (result) {
          result = result + "you have passed the first then()";
          $scope.status = result;
          return result;
        }, function (error) {
          error = error + "failed but you have passed the first then()";
          $scope.status = error;
          return error;
        }).then(function (result) {
          alert("Success: " + result);
        }, function (error) {
          alert("Fail: " + error);
        })
      }
    }]);
</script>

為什麼當我$scope.flag為false的時候第一個then走是error而第二個走的是success，要改的話改怎麼改

Answer 1

雷雷

Answer 2

每個.then都會回傳一個新的promise。新的promise執行失敗的程式碼後，會resolve目前傳入.then的函數的回傳值。因此第二個執行的是success。

這問題說多了也沒用，自己看promise源碼，一下就清楚了。