coffeescript - $q defer 和 Promise 以及如何使用它们在渲染 View 之前为 Controller 加载数据

Question

这是我发现的最相关的事情:https://stackoverflow.com/a/11972028/110233

当我只想返回一个东西时，它似乎工作得很好，但是当其他东西依赖于第一件事时，我不确定如何返回多个东西。

因为这有点迟钝，这里有一个关于我当前正在做的事情的小例子:

window.EventRosterCtrl = ($scope, subevent) ->
    $scope.subevent = subevent

EventRosterCtrl.resolve = 
    subevent: (SubEvent, $route) ->
        deferred = $q.defer()

        SubEvent.get {subevent_id: $route.current.pathParams.subevent_id}, (subevent) ->
            deferred.resolve subevent

        return deferred.promise

这是我想要做的一个例子:

window.EventRosterCtrl = ($scope, subevent, addresses) ->
    $scope.subevent = subevent
    $scope.addresses = addresses

EventRosterCtrl.resolve = 
    subevent: (SubEvent, $route) ->
        deferred = $q.defer()

        SubEvent.get {subevent_id: $route.current.pathParams.subevent_id}, (subevent) ->
            deferred.resolve subevent

        return deferred.promise

    addresses: (User) ->
        deferred = $q.defer()

        # how do you get subevent called first and how would you access it here?
        for participant in subevent.participants
            User.get {user_id: participant.user}, (user) ->
                addresses[participant._id] = user.address

        deferred.resolve addresses

        return deferred.promise

Answer 1

您需要使用 .then() 链接 Promise

  var promise = firstOperation();
  promise = promise.then(function(value) {
    // do some more work
    return value; // it can be another promise
  });
  return promise; // this one will be resolved when both steps are resolved