Angular - returning promise.then from function

Question

I have never looked at angular before and I am working on a project that uses it extensively, I am quite confused by the promise api code.

If a function returns promise.then (which I gather is called when the promise is fulfilled) is this the result of the promise function? Is there any blocking when you do this as the result isnt immediately available?

A crude example:

$scope.refreshFilters = function (filters) {
    var promise;
    promise = getConfig(filters);
    return promise.then(function (data) {
        return data.availableContent;
    });
};

Do calls to the refreshFilters function need to block now because the result isnt available immediately?

mikefrey · Accepted Answer · 2016-03-07 14:42:43Z

2

Correct, promise.then(...) itself returns a promise. You can find the Promise A+ spec, which $q mostly follows here: https://promisesaplus.com/

A promise is a way of handling asynchronous work. In your example, getConfig(filters) returns a promise, which is handled with the .then(...) call. And refreshFilters returns a promise because getConfig(filters).then(...) also returns a promise. If getConfig executes asynchronously, then refreshFilters will as well.

answered Mar 7, 2016 at 14:42

mikefrey

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Eyescream · Accepted Answer · 2016-03-07 14:43:18Z

2

The return inside the "then" returns a promise not the plain value, so

return promise.then(function (data) {                    
                return data.availableContent;
            });
};

is actually returning a promise.

answered Mar 7, 2016 at 14:43

Eyescream

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1 Comment

billc.cn Over a year ago

... which resolves to the value returned by the function supplied to then()

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