Is it considered a bad practice to request data from the server in a service constructor in Angular?

Question

I have an angular service that is responsible for representing a collection of employees (that happens to be stored on the database normally). I hear that it is bad code smell to do a $http.get request inside the service's class's constructor. What I have been told is that I am supposed to inject the dependency that allows you to collect the relevant data but isn't that what I'm doing by using $http, using dependency injection?

So is it bad form to simply do var employees = $http.get('employees') from the server?

Many thanks!

Answer 1

Service is your model, all call to your server should be centralized in services.

If i start from your example you should have an "EmployeeService" And in it a function like that : (don't forget to inject $q and $http services)

me = this;
me.cacheEmployee = null;
me.getEmployees = function(){
    var deferred = $q.defer();
    if(me.cacheEmployee != null){
        deferred.resolve(me.cacheEmployee);
    }else{
       $http.get('urlToEmployee').success(function(result){
           me.cacheEmployee = result;
           deferred.resolve(me.cacheEmployee);
       });
    }

    return deferred.promise;
};
me.forceLoadEmployee = function(){ // after each CreateUpdateDelete operations
    var deferred = $q.defer();
    $http.get('urlToEmployee').success(function(result){
        me.cacheEmployee = result;
        deferred.resolve(me.cacheEmployee);
    });
    return deferred.promise;
};

And in the controller of the page you want to display your employees (don't forget to inject EmployeeService)

EmployeeService.getEmployees().then(function(result){
   $scope.employees = result;
});

You use asynchronous call, you can't think in procedural way to resolve your problem.

A basic doc about promise : https://docs.angularjs.org/api/ng/service/$q

I hope my answer will fit you.

Have a nice day !

Edit : now you have a list of employee in cache, the call will be launched to the server only the first time.