Exploring various data promises in AngularUI router

Question

Exploring various data promises in AngularUI router

I am attempting to utilize the $q service to resolve multiple promises using the $q.all() function with AngularUI router. However, I am encountering issues where it is failing or not functioning as expected.

This snippet is from my configuration file that includes the $stateProvider:

.state('home.team',
{
    url : '^/team',
    views : {
        'main' : {
            templateUrl : ConfigProvider.path.views + '/segment/home/team.html',
            controller : 'SegmentHomeTeamCtrl',
            resolve : {
                promiseData : function(ResolveService) { return ResolveService.resolveHomeTeam(); }
            }
        },
        'subMenu' : {
            templateUrl : ConfigProvider.path.views + '/menu/home/team.html'
        }
    }
});

Here is the resolveHomeTeam function found in the Resolve service:

function resolveHomeTeam()
{
    var promises = [];
    promises.push($q.defer());
    UserService.team('me', function(data)
    {
        promises[0].resolve(data);
    }, function()
    {
        promises[0].reject();
    });

    return $q.all(promises);
}

In this scenario, only one promise is being added to the array and it is known to be resolved.

If the single promise is resolved, shouldn't the promise returned by $q.all() also be resolved? And should the data from promiseData be injected into the SegmentHomeTeamCtrl controller?

When trying to display promiseData within the SegmentHomeTeamCtrl controller, the entire promise is received back along with the actual server data, but there are difficulties in accessing it.

javascript angularjs angular-ui-router

Answer 1

Answer №1

Your code is facing an issue because you are inserting a deferred into your array instead of a promise.

It's worth noting that deferreds are becoming less popular. It is now recommended to create a promise (which aligns with ES6 APIs) using a promise constructor:

function resolveHomeTeam() {
    var promises = [];

    promises.push($q(function (resolve, reject) {
        UserService.team('me', resolve, reject);
    }));

    return $q.all(promises);
}

This approach also helps in making your code more concise and readable.

If desired, you can combine all of this into a single statement:

function resolveHomeTeam() {
    return $q.all([
        $q(function (resolve, reject) {
            UserService.team('me', resolve, reject);
        })
    ]);
}

Answer 2

Your code is facing an issue because you are inserting a deferred into your array instead of a promise.

It's worth noting that deferreds are becoming less popular. It is now recommended to create a promise (which aligns with ES6 APIs) using a promise constructor:

function resolveHomeTeam() {
    var promises = [];

    promises.push($q(function (resolve, reject) {
        UserService.team('me', resolve, reject);
    }));

    return $q.all(promises);
}

This approach also helps in making your code more concise and readable.

If desired, you can combine all of this into a single statement:

function resolveHomeTeam() {
    return $q.all([
        $q(function (resolve, reject) {
            UserService.team('me', resolve, reject);
        })
    ]);
}

Answer 3

Answer №2

You're on the right track with your approach, returning a promise generated by $q.all and resolving it as needed.

The issue lies in the fact that you are not creating an array of promises, but instead, you are pushing a deferred object into the array.

To fix this, modify your code as follows:

var promises = [];
var teamDefer = $q.defer();
promises.push(teamDefer.promise);

UserService.team('me', function(data)
{
   teamDefer.resolve(data);
}, function()
{
   teamDefer.reject();
});

Then proceed to return $q.all() (as previously done):

return $q.all(promises);

Slightly off-topic:

The variable name promiseData may be misleading and could lead to confusion. It's advisable to name it after the result you expect to receive. This is what will be used in your controller, regardless of whether it originates from a promise or not. Consider renaming it to something like team.

Answer 4

You're on the right track with your approach, returning a promise generated by $q.all and resolving it as needed.

The issue lies in the fact that you are not creating an array of promises, but instead, you are pushing a deferred object into the array.

To fix this, modify your code as follows:

var promises = [];
var teamDefer = $q.defer();
promises.push(teamDefer.promise);

UserService.team('me', function(data)
{
   teamDefer.resolve(data);
}, function()
{
   teamDefer.reject();
});

Then proceed to return $q.all() (as previously done):

return $q.all(promises);

Slightly off-topic:

The variable name promiseData may be misleading and could lead to confusion. It's advisable to name it after the result you expect to receive. This is what will be used in your controller, regardless of whether it originates from a promise or not. Consider renaming it to something like team.

Exploring various data promises in AngularUI router

Answer №1

Answer №2

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