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Can some one explain me how does $q.when work in AngularJS? I'm trying to analyse how $http work and found this:
var promise = $q.when(config); And here is config object from Chrome console:
Object {transformRequest: Array[1], transformResponse: Array[1], cache: Object, method: "GET", url: "/schedule/month_index.html"…} cache: Object headers: Object method: "GET" transformRequest: Array[1] transformResponse: Array[1] url: "/schedule/month_index.html" __proto__: Object What happens next? How this object get's resolved or rejected?
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$q is integrated with the $rootScope. Scope Scope model observation mechanism in AngularJS, which means faster propagation of resolution or rejection into your models and avoiding unnecessary browser repaints, which would result in flickering UI. Q has many more features than $q, but that comes at a cost of bytes.
Simply put you can use $q. defer() to create a Promise. A Promise is a function that returns a single value or error in the future. So whenever you have some asynchronous process that should return a value or an error, you can use $q. defer() to create a new Promise.
IPromise , basically if you are using vs and as a suggestion when you hover over a particular method it will tell you what type it returns and you can derive the return type from that.
$http is an AngularJS service for reading data from remote servers.
Calling $q.when takes a promise or any other type, if it is not a promise then it will wrap it in a promise and call resolve. If you pass a value to it then it is never going to be rejected.
From the docs:
Wraps an object that might be a value or a (3rd party) then-able promise into a $q promise. This is useful when you are dealing with an object that might or might not be a promise, or if the promise comes from a source that can't be trusted.
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