行为与承诺回调混淆

Question

Does anyone know how this works?

When I declare a Promise in a typescript angularjs class like this:

 constructor() { var promise = customService.getObjects(); promise.then( $scope.successCallback, $scope.errorCallback); $scope.successCallback = () => {} $scope.errorCallback= () => {} } 

...these callbacks won't run when the promise resolves. When I declare them first and then run the promise, then the callbacks work fine. like this:

 constructor() { $scope.successCallback = () => {} $scope.errorCallback= () => {} var promise = customService.getObjects(); promise.then( $scope.successCallback, $scope.errorCallback); } 

Is this some tricky javascript/typescript thing? It seems quite illogical to me.

Answer 1

That's because you're just passing 'undefined' into .then() in the first case. Do the functions need to be attached to $scope? Can you just make an anonymous function than are defined inside then()? Or you could make these functions themselves call the ones which are attached to $scope and not yet defined.