如何发出多个http请求？

Question

I have an HTTP request in my parent and child controller:

Parent controller

//Product is a $resource object that return http request as a promise.
Product.getItem()
   .then(function(items) {
      $scope.items = items
      //do something in the parent controller.
})

Child controller

Product.getItem()
   .then(function(items) {          
      $scope.items = items
      //do something in the child controller
})

Product Factory

angular.module('testApp').factory('Product', function($http,$q) {
    var service = {}
    service.getItem = function() {
        return http.$get('api/url');
    }
    return service; 
})

Child controller is launched when I am in certain pages. The problem is when I launch those pages, the codes will make double http request to api/url because parent and child controllers both make the requests. Although my app still works, I was wondering if there is a better way to solve it. thanks for the help!

Answer 1

EDIT: I investigated Phil's comments a bit, and fixed (rewrote) my example. The plunker at the bottom reflects these changes. Here is the updated code:

app.controller('MainCtrl', function($scope, getStore) {
  getStore.get().then(function(data) {
    $scope.data = data
  })
});
app.controller('ChildCtrl', function($scope, $timeout, getStore) {
  $timeout(function() {
    getStore.get().then(function(data) {
      $scope.test = data
    })
  },3000)

});

app.factory('getStore', function($http, $q) {
  var self = this;
  var data;
  return {
    get: function() {
      if (data) {
        console.log(data);
        console.log('already got data')
        return $q.when(data)
      } else {
        data = $http.get('test.json')
        .then(function(response) {
          console.log('fetched data')
          return response.data;
        })
        return data
      }
    }
  }
})

---

Here is one solution - separate your $http.get to a factory and store the value there. Factories are singletons, so both controllers can access and check the data.

JS:

app.controller('MainCtrl', function($scope, getStore) {
  $scope.data = getStore.get()
});
app.controller('ChildCtrl', function($scope, $timeout, getStore) {
  $timeout(function() {
    $scope.data = getStore.get()
    var check = getStore.checkData();
    console.log('Data in store: ' + angular.toJson(check));

  },1000)
  $scope.getData = function() {
    console.log(getStore.get());
  }
});

app.factory('getStore', function($http) {
  var self = this;
  return {
    data: undefined,
    get: function() {
      if (self.data) {
        console.log('already got data')
        return self.data
      } else {
        $http.get('test.json')
        .success(function(data) {
          console.log('no data found');
          self.data = data;
          console.log(self.data);
          return self.data;
        })
      }
    }
  }
})

It just runs a check to see whether the value is already stored or not, and then returns it if it is, and if not, it gets, stores, and returns it.

Plunker