Retrieve information using AngularJS only when it is not yet defined

Question

Retrieve information using AngularJS only when it is not yet defined

Currently, I am using $http in a controller to retrieve data and display it to the user. However, once the data is fetched for the first time, I do not want to fetch it again when moving between different tabs or controllers. My expertise lies in web development and AngularJS, but I am struggling to prevent the repeated fetching of data. The code snippet below was my attempt at achieving this, but unfortunately, the data is still being fetched every time.

// Check if data has already been retrieved
if (angular.isDefined($scope.data)) {
    console.log("Data already exists, no need to fetch again");
    return;
} else {
    console.log("Fetch data for the first time");
}

$http.post('/api/data'......

javascript angularjs http

Answer 1

Answer №1

It seems like the issue may be related to the different scopes of your tab controllers, causing $scope.data to not be defined for the second tab controller in the limited code example provided.

While you could consider placing the data on $rootScope, it is generally not recommended due to potential issues with global variables.

Additionally, there may be a race condition present where switching tabs before data arrival could trigger a duplicate request.

A more effective solution would involve utilizing a service that can cache the promise and provide it to subsequent callers:

.factory("fooSvc", function($http){
  var promise;
  return {
    getData: function(){
       if (promise) return promise;
       promise = $http.get("/some/url").then(function(response){
         // Optionally process the response
         return response.data;
       });

       return promise;
    }
  }
})

By employing this service in your controller, you can effortlessly retrieve the data without concerns about redundant requests:

.controller("TabCtrl1", function($scope, fooSvc){
   fooSvc.getData().then(function(data){
     $scope.data = data;
   })
}

Answer 2

It seems like the issue may be related to the different scopes of your tab controllers, causing $scope.data to not be defined for the second tab controller in the limited code example provided.

While you could consider placing the data on $rootScope, it is generally not recommended due to potential issues with global variables.

Additionally, there may be a race condition present where switching tabs before data arrival could trigger a duplicate request.

A more effective solution would involve utilizing a service that can cache the promise and provide it to subsequent callers:

.factory("fooSvc", function($http){
  var promise;
  return {
    getData: function(){
       if (promise) return promise;
       promise = $http.get("/some/url").then(function(response){
         // Optionally process the response
         return response.data;
       });

       return promise;
    }
  }
})

By employing this service in your controller, you can effortlessly retrieve the data without concerns about redundant requests:

.controller("TabCtrl1", function($scope, fooSvc){
   fooSvc.getData().then(function(data){
     $scope.data = data;
   })
}

Retrieve information using AngularJS only when it is not yet defined

Answer №1

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