angular-singleton-promise

An AngularJS service that protects your asynchronous code against multiple identical requests.

Basically, what it does is to help you avoid constructs like this:

var customerSearchDeferred = null;
var customerSearchInProgress = false;

function getCustomers(filter) {
    if (customerSearchInProgress) {
        return customerSearchDeferred.promise;
    }
    customerSearchDeferred = $q.defer();
    customerSearchInProgress = true;
    DataService.search('api/customers', filter)
        .then(function (data) {
            customerSearchDeferred.resolve(data.results);
        })
        .catch(function (data) {
            customerSearchDeferred.reject(data);
        })
        .finally(function () {
            customerSearchInProgress = false;
        });
    return customerSearchDeferred.promise;
}

...and instead use something like this:

function getCustomers(filter) {
    return SingletonPromise({
        context: "customers",
        varyBy: filter,
        fn: function () {
            return DataService.search('api/customers', filter);
        }
    });
}

##Installation Install via bower

bower install angular-singleton-promise --save

##Usage Make sure you have loaded the necessary scripts in the correct order. Add angular-singleton-promise as a module dependency, like so:

var app = angular('app', ['angular-singleton-promise']);

Then just inject the SingletonPromise service in your own service:

angular
    .module('app')
    .service('DataService', DataService);

DataService.$inject = ['SingletonPromise'];

##Configuration Behind the scenes, the SingletonPromise service caches the wrapped function using the string representation of the function itself as key. To make it more flexible (and to allow for identical functions in different contexts) the service provides a config object that takes two optional parameters:

• fn: the function you want to wrap
• context: a string value that gets prepended to the function signature to make the key unique
• varyBy: an object that gets serialized and appended to the key