Retrieving data efficiently: utilizing caching in an AngularJS service to store data fetched from a single $http request

Question

Retrieving data efficiently: utilizing caching in an AngularJS service to store data fetched from a single $http request

Forgive me if this question seems simple or silly, but I find myself in a new scenario and need some guidance. In my AngularJS app, I have a service with 4 methods that share about 80% of the same functionality and code. I want to optimize this and make it more efficient. Here is a simplified version of my service:

    .factory('townDataService', function ($http) {

        var townList = {};

        townList.getTownList = function () {

            return $http({method: 'GET', url: '/api/country/cities'})
                .then(function (response) {

                    // Formatting the response data here...
                    var returnArray = [];
                    // Looping through the countries
                    var JsonData = response.data;

                    for (key in JsonData['countries']) {
                         // Formatting code...
                    }
                    // End of repeated code

                    return returnArray;

                });
        };


     townList.getCurrentTown = function (place) {

            return $http({method: 'GET', url: '/api/country/cities'})
                .then(function (response) {

                    // Formatting the response data here...
                    var returnArray = [];
                    // Looping through the countries
                    var JsonData = response.data;

                    for (key in JsonData['countries']) {
                         // Formatting code...
                    }
                    // End of repeated code

                    // Further working with the returnArray...
                    for (var i = 0; i < returnArray.length; i++) {
                        // Do something
                    }
                    return currentTown;

                });
        };


        townList.getCurrentCountry = function (place) {

            return $http({method: 'GET', url: '/api/country/cities'})
                .then(function (response) {

                    // Formatting the response data here...
                    var returnArray = [];
                    // Looping through the countries
                    var JsonData = response.data;

                    for (key in JsonData['countries']) {
                         // Formatting code...
                    }
                    // End of repeated code

                    // Further working with the returnArray...
                    for (var i = 0; i < returnArray.length; i++) {
                        // Do something
                    }
                    return currentCountry;

                });
        };

        return townList;

    }
);

I realize that I am repeating the same $http 'GET' request and formatting code in each method, which is not efficient. What is the best approach to centralize this functionality in its own function so that the GET request is only made once, but each method still returns a promise? Should I store the results of the $http request in a variable and inject it into each method before formatting the data? Or should I utilize a $cacheFactory?

I apologize if my question is unclear, and I appreciate any help you can provide.

Thank you.

javascript angularjs angularjs-service

Answer 1

Answer №1

As you mentioned, there are several ways to refactor this code for better organization and efficiency. One approach could involve separating the HTTP handling and caching into a dedicated service, while the formatting logic could be placed in a separate method:

The HTTP handling service:

.service('townHttpService', function($http, $q) {
    var cache;

    function getCities() {
        var d = $q.defer();
        if( cache ) {
            d.resolve(cache);
        }
        else {
            $http({method: 'GET', url: '/api/country/cities'}).then(
                function success(response) {
                    cache = response.data;
                    d.resolve(cache);
                },
                function failure(reason) {
                    d.reject(reason);
                }
            });
        }
        return d.promise;
    }

    function clearCache() {
        cache = null;
    }

    return {
        getCities: getCities,
        clearCache: clearCache
    };
})

The formatter:

.service('townFormatter', function() {
    return function townFormatter(jsonData) {
        // Code for formatting the response...
        var returnArray = [], key;
        // Loop through the countries
        for (key in jsonData['countries']) {
             // Formatting logic...
        }
        return returnArray; // The formatted array
    };
})

Refactoring your townDataService using the above services:

.factory('townDataService', function (townHttpService, townFormatter) {

    var townList = {};

    townList.getTownList = function () {
        return townHttpService.getCities().then(townFormatter);
    };

    townList.getCurrentTown = function (place) {
        return townHttpService.getCities().then(townFormatter).then(function(cityList) {
            var currentTown;
            for (var i = 0; i < cityList.length; i++) {
                // Perform operations
            }
            return currentTown; // Resulting string
        });
    };

    townList.getCurrentCountry = function (place) {
        return townHttpService.getCities().then(townFormatter).then(function(cityList) {
            var currentCountry;
            for (var i = 0; i < cityList.length; i++) {
                // Perform operations
            }
            return currentCountry; // Resulting string
        });

    return townList;
})

Answer 2

As you mentioned, there are several ways to refactor this code for better organization and efficiency. One approach could involve separating the HTTP handling and caching into a dedicated service, while the formatting logic could be placed in a separate method:

The HTTP handling service:

.service('townHttpService', function($http, $q) {
    var cache;

    function getCities() {
        var d = $q.defer();
        if( cache ) {
            d.resolve(cache);
        }
        else {
            $http({method: 'GET', url: '/api/country/cities'}).then(
                function success(response) {
                    cache = response.data;
                    d.resolve(cache);
                },
                function failure(reason) {
                    d.reject(reason);
                }
            });
        }
        return d.promise;
    }

    function clearCache() {
        cache = null;
    }

    return {
        getCities: getCities,
        clearCache: clearCache
    };
})

The formatter:

.service('townFormatter', function() {
    return function townFormatter(jsonData) {
        // Code for formatting the response...
        var returnArray = [], key;
        // Loop through the countries
        for (key in jsonData['countries']) {
             // Formatting logic...
        }
        return returnArray; // The formatted array
    };
})

Refactoring your townDataService using the above services:

.factory('townDataService', function (townHttpService, townFormatter) {

    var townList = {};

    townList.getTownList = function () {
        return townHttpService.getCities().then(townFormatter);
    };

    townList.getCurrentTown = function (place) {
        return townHttpService.getCities().then(townFormatter).then(function(cityList) {
            var currentTown;
            for (var i = 0; i < cityList.length; i++) {
                // Perform operations
            }
            return currentTown; // Resulting string
        });
    };

    townList.getCurrentCountry = function (place) {
        return townHttpService.getCities().then(townFormatter).then(function(cityList) {
            var currentCountry;
            for (var i = 0; i < cityList.length; i++) {
                // Perform operations
            }
            return currentCountry; // Resulting string
        });

    return townList;
})

Answer 3

Answer №2

It seems like you have two inquiries regarding streamlining code and implementing an efficient caching strategy.

Streamlining code: The method townList.getTownList appears to be a central function, with the other two methods serving as extensions of it. In order to eliminate duplicate code,

townList.getCurrentTown = function(place) {
  var towns = townList.getTownList();
  for (var i = 0; i < returnArray.length; i++) { //additional stuff
  }
  return currentTown;
};


townList.getCurrentCountry = function(place) {
  var towns = townList.getTownList();
  for (var i = 0; i < returnArray.length; i++) { //additional stuff
  }
  return currentCountry;
};

Implementing caching: Currently, the http call is only made in townList.getTownList, making it a suitable place to incorporate a caching mechanism. The decision to cache data depends on whether it is a one-time fetch or requires periodic refresh. One-time fetch: Simply enable caching in the http call

$http({method: 'GET', url: '/api/country/cities', cache:true});

Refresh based on request: One approach is to introduce a refresh parameter to trigger data refresh when necessary. If the refresh flag is true or the townList is empty, new data will be fetched.

var srvc = this;
var townList;
townList.getTownList = function(refresh ) {
  if (refresh || !townList) {
    srvc.townList = $http({
      method: 'GET',
      url: '/api/country/cities'
    })
      .then(function(response) {
        var returnArray = [];
        var JsonData = response.data;
        for (var key in JsonData.countries) {}
        return returnArray; // the data is returned as an array without any formatting
      });
  }

  return townList;
};

Answer 4

It seems like you have two inquiries regarding streamlining code and implementing an efficient caching strategy.

Streamlining code: The method townList.getTownList appears to be a central function, with the other two methods serving as extensions of it. In order to eliminate duplicate code,

townList.getCurrentTown = function(place) {
  var towns = townList.getTownList();
  for (var i = 0; i < returnArray.length; i++) { //additional stuff
  }
  return currentTown;
};


townList.getCurrentCountry = function(place) {
  var towns = townList.getTownList();
  for (var i = 0; i < returnArray.length; i++) { //additional stuff
  }
  return currentCountry;
};

Implementing caching: Currently, the http call is only made in townList.getTownList, making it a suitable place to incorporate a caching mechanism. The decision to cache data depends on whether it is a one-time fetch or requires periodic refresh. One-time fetch: Simply enable caching in the http call

$http({method: 'GET', url: '/api/country/cities', cache:true});

Refresh based on request: One approach is to introduce a refresh parameter to trigger data refresh when necessary. If the refresh flag is true or the townList is empty, new data will be fetched.

var srvc = this;
var townList;
townList.getTownList = function(refresh ) {
  if (refresh || !townList) {
    srvc.townList = $http({
      method: 'GET',
      url: '/api/country/cities'
    })
      .then(function(response) {
        var returnArray = [];
        var JsonData = response.data;
        for (var key in JsonData.countries) {}
        return returnArray; // the data is returned as an array without any formatting
      });
  }

  return townList;
};

Answer 5

Answer №3

To optimize your code and streamline its performance, consider caching your GET response and refactoring to eliminate redundancy. Here is an example of how you can achieve this:

.factory('cityDataService', function ($http) {
    var getCitiesAsync = function(){
        return $http({method: 'GET', url: '/api/country/cities', cache:true});
    };

    var cityList = {};

    cityList.getCityList = function () {
        return getCitiesAsync().then(prepareCityList);
    };

    var prepareCityList = function(response){
        //extract cities and customize as needed
        return result;
    };

    ...

Using $cacheFactory might be unnecessary in this context, as the built-in cache option can suffice for simpler scenarios.

Answer 6

To optimize your code and streamline its performance, consider caching your GET response and refactoring to eliminate redundancy. Here is an example of how you can achieve this:

.factory('cityDataService', function ($http) {
    var getCitiesAsync = function(){
        return $http({method: 'GET', url: '/api/country/cities', cache:true});
    };

    var cityList = {};

    cityList.getCityList = function () {
        return getCitiesAsync().then(prepareCityList);
    };

    var prepareCityList = function(response){
        //extract cities and customize as needed
        return result;
    };

    ...

Using $cacheFactory might be unnecessary in this context, as the built-in cache option can suffice for simpler scenarios.

Answer 7

Answer №4

To prevent potential timing issues, it may be advantageous to enhance the solution by extending it slightly:

function retrieveCities() {
        var deferred = $q.defer();
        if( cityCache ) {
            deferred.resolve(cityCache);
        }
        else {
            $http({method: 'GET', url: '/api/country/cities'}).then(
                function success(response) {
                    if (!cityCache) {
                        cityCache = response.data;
                    }
                    deferred.resolve(cityCache);
                },
                function failure(reason) {
                    deferred.reject(reason);
                }
            });
        }
        return deferred.promise;
    }

Upon subsequent calls to the webservice that result in success, it is important to check if the cityCache variable was set while awaiting the server response. If the cache has been populated, we can simply return the existing value. This approach ensures that the variable cityCache is not overwritten with new data if multiple requests are made:

function success(response) {
    if (!cityCache) {
        cityCache = response.data;

While this may not always pose an issue, it can be especially beneficial in scenarios where identical object instances are required (such as in data binding) to guarantee that data is fetched only once!

Answer 8

To prevent potential timing issues, it may be advantageous to enhance the solution by extending it slightly:

function retrieveCities() {
        var deferred = $q.defer();
        if( cityCache ) {
            deferred.resolve(cityCache);
        }
        else {
            $http({method: 'GET', url: '/api/country/cities'}).then(
                function success(response) {
                    if (!cityCache) {
                        cityCache = response.data;
                    }
                    deferred.resolve(cityCache);
                },
                function failure(reason) {
                    deferred.reject(reason);
                }
            });
        }
        return deferred.promise;
    }

Upon subsequent calls to the webservice that result in success, it is important to check if the cityCache variable was set while awaiting the server response. If the cache has been populated, we can simply return the existing value. This approach ensures that the variable cityCache is not overwritten with new data if multiple requests are made:

function success(response) {
    if (!cityCache) {
        cityCache = response.data;

While this may not always pose an issue, it can be especially beneficial in scenarios where identical object instances are required (such as in data binding) to guarantee that data is fetched only once!

Retrieving data efficiently: utilizing caching in an AngularJS service to store data fetched from a single $http request

Answer №1

Answer №2

Answer №3

Answer №4

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