我是不是正确返回这个诺言？ [英] Am I returning this promise correctly?
问题描述
我有一个函数，getMonitors一个服务里面。 getMonitors返回监控对象的列表。如果显示器的对象是空的，它通过http抓住显示器和存储监控对象数组中的对象，然后返回。该功能为codeD当成了承诺。我知道HTTP返回一个承诺，但我的功能可能会或可能不会使用http - 所以我用我自己的诺言覆盖（请参阅下面的code）
I have a function, getMonitors inside a service. getMonitors returns a list of monitor objects. If the monitor object is empty, it grabs the monitors via http and stores the objects in a monitor object array and then returns it. The function is coded as a promise. I know http returns a promise, but my function may or may not use http - so I've overlaid it with my own promise (see below for code)
控制器可以调用getMonitors（0）或getMonitors（1）。 0意味着，如果其已加载的显示器阵列由于previous电话，不要再加载它。 （1）指力重新从HTTP
Controllers can call getMonitors(0) or getMonitors(1). 0 means if its already loaded in the monitors array due to a previous call, don't load it again. (1) means force reload the array from HTTP
服务和相关getMonitors为codeD方式如下：
The service and associated getMonitors is coded the following way:
angular.module('zmApp.controllers').service('ZMDataModel', ['$http', '$q',
function($http, $q) {
// var deferred='';
var monitorsLoaded = 0;
var monitors = [];
getMonitors: function(forceReload) {
console.log("** Inside ZMData getMonitors with forceReload=" + forceReload);
var d = $q.defer();
if ((monitorsLoaded == 0) || (forceReload == 1)) // monitors are empty or force reload
{
console.log("ZMDataModel: Invoking HTTP Factory to load monitors");
var apiurl = loginData.apiurl;
var myurl = apiurl + "/monitors.json";
$http.get(myurl)
.success(function(data) {
// console.log ("HTTP success got " + JSON.stringify(data));
monitors = data.monitors;
console.log("promise resolved inside HTTP success");
monitorsLoaded = 1;
return d.resolve(monitors);
})
.error(function(err) {
console.log("HTTP Error " + err);
monitors = [];
console.log("promise resolved inside HTTP fail");
// I know I need to reject here, not resolve. I'll get to it. For now lets assume I need an empty monitors list if there was an error
return d.resolve(monitors);
});
console.log("promise deferred inside HTTP inside getMonitors");
return d.promise;
} else // monitors are loaded
{
console.log("Returning pre-loaded list of " + monitors.length + " monitors");
return d.resolve(monitors);
}
},
我已经设置了getMonitors像这样的依赖路线：
I have a route set up with getMonitors as a dependency like so:
.state('app.montage', {
data: {
requireLogin: false
},
resolve: {
message: function(ZMDataModel) {
console.log("Inside app.montage resolve");
return ZMDataModel.getMonitors(0);
}
},
url: "/montage",
views: {
'menuContent': {
templateUrl: "templates/montage.html",
controller: 'zmApp.MontageCtrl',
}
}
})
使用这个样本控制器是codeD，像这样：
A sample controller that uses this is coded like so:
angular.module('zmApp.controllers').controller('zmApp.MontageCtrl', function($scope, $rootScope, ZMDataModel, message) {
$scope.monitors = [];
console.log("Inside MontageCtrl waiting for monitors to load...");
$scope.monitors = message;
// this line returns undefined when getMonitors tries to return a preloaded monitor list
console.log("I have received the monitors inside Montage and there are " + $scope.monitors.length);
// console.log("***CALLING FACTORY");
//ZMHttpFactory.getMonitors().then(function(data) //{
// $scope.monitors = data;
// console.log("I GOT " + $scope.monitors);
// });
$scope.doRefresh = function() {
console.log("***Pull to Refresh");
$scope.monitors = [];
var refresh = ZMDataModel.getMonitors(1);
refresh.then(function(data) {
$scope.monitors = data;
$scope.$broadcast('scroll.refreshComplete');
});
};
});
我面临的问题是，这是第一次运行时，显示器列表是空的，所以ZMData从HTTP URL加载监视器和视图完美展现。当我切换到另外的看法，回到这个观点，我把它记录了ZMData正在恢复显示器的preloaded列表（我知道他们正在填充，因为我打印出在ZMData getMonitor其他部分的计数）。然而，被返回到控制器是不确定的，当getMonitors的else部分的打击。
The problem I am facing is that the first time this is run, the monitors list is empty so ZMData loads the monitors from the HTTP url and the view shows perfectly. When I switch to another view and back to this view, I see it logs that ZMData is returning the preloaded list of monitors (I know they are populated because I am printing out the count in ZMData getMonitor else section). However, what is being returned to the controller is undefined when the "else" part of getMonitors hit.
这可能意味着我不是getMonitors正确返回的承诺别人的一部分。
This likely means I am not returning the promise correctly in getMonitors "else" part.
任何帮助将AP preciated
Any help would be appreciated
推荐答案
嗯，我终于包裹着我身边的诺言的头。
我们不能回到d.resolve（）。这只是设置的状态。你总是需要返回d.promise，它如果得到解决，它将返回的决心。人。这驱使我mad.I想，我终于得到了承诺的基本窍门后3个不同的做题。我希望做更清楚的教程。每个人都只能回到d.promise，没有人真正解释清楚，d.promise返回承诺的状态 - 这是由决心改变或拒绝
Ah, I finally wrapped my head around promises. We can't return d.resolve(). That just sets a state. You always need to return d.promise and it if was resolved, it will return the resolve. Man. This drove me mad.I think I finally got the basic hang of promises after 3 different SO questions. I wish tutorials made this clearer. Everyone was only returning d.promise and no one really explained clearly that d.promise returns the state of the promise - which is changed by resolve or reject.
正确的code是：
getMonitors: function (forceReload) {
console.log ("** Inside ZMData getMonitors with forceReload="+forceReload);
var d = $q.defer();
if ((monitorsLoaded == 0) || (forceReload == 1)) // monitors are empty or force reload
{
console.log ("ZMDataModel: Invoking HTTP Factory to load monitors");
var apiurl = loginData.apiurl;
var myurl = apiurl+"/monitors.json";
$http.get(myurl)
.success(function(data)
{
// console.log ("HTTP success got " + JSON.stringify(data));
monitors = data.monitors;
console.log ("promise resolved inside HTTP success");
monitorsLoaded = 1;
d.resolve(monitors);
})
.error (function (err)
{
console.log ("HTTP Error " + err);
monitors = [];
console.log ("promise resolved inside HTTP fail");
d.resolve (monitors);
});
return d.promise;
}
else // monitors are loaded
{
console.log ("Returning pre-loaded list of "+monitors.length+" monitors");
d.resolve(monitors);
return d.promise;
}
}
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