I need two instances of AngularJS $http service or what? - http

Question

I want add a response interceptor to my $http service for error handling purposes. The interceptor logic include send errors messages to server using $http in case necessary, BUT I don't want send errors messages to the server about errors messages, I mean, I want disable my interceptor while sending error message to the server.
My idea was create a service named 'remote_log' and put inside it all the code needed to send error to server. That service of course will use the $http service and have it in its dependency list.
Then add as dependency of the interceptor to the 'remote_log' service, and use the 'remote_log' inside the interceptor when need send errors to the server. The problems is that:
Interceptors must be defined using the $httpProvider when the $http service still is not instantiated/accessible, so, inside the interceptor code can't be a dependency to that the $http service because a "Circular dependency" error happen.
I think my only option is create a separate instance of the $http service inside my 'remote_log', an instance that don't uses the $httpProvider configuration I set while creating the interceptor. My question is: How can I do that? Any other ideas?

Answer 1

1. Circular dependency problem.
So, why does the error appear? Here is a quick overview of the process:
$http service is requested.
$httpProvider is asked to construct it.
During construction you register interceptor, that requests $http service not existing yet.
You get "Circular dependency" error.
First solution.
Create your dependency using angular.injector(). Notice, that you will create another $http service, independent from your app.
$httpProvider.interceptors.push(function($q) {
$injector = angular.injector();
return {
response: function(response) {
$injector.invoke(function($http) {
// This is the exterior $http service!
// This interceptor will not affect it.
});
}
};
});
Second solution (better).
Inject $injector in your interceptor and use it to retrieve dependencies after $http initialization, right at the time you need them. These dependencies are registered services of your app and will not be created anew!
$httpProvider.interceptors.push(function($q, $injector) {
return {
response: function(response) {
$injector.invoke(function($http, someService) {
// $http is already constructed at the time and you may
// use it, just as any other service registered in your
// app module and modules on which app depends on.
});
}
};
});
2. Interception prevention problem.
If you use the second solution, there are actually two problems:
If you utilize $http service inside your
interceptor, you may end up with infinite interceptions: you send
request, interceptor catches it, sends another, catches another,
send again, and so on.
Sometimes you want just prevent request from being intercepted.
The 'config' parameter of $http service is just an object. You may create a convention, providing custom parameters and recognizing them in your interceptors.
For example, let's add "nointercept" property to config and try duplicate every user request. This is a silly application, but useful example to understand the behavior:
$httpProvider.interceptors.push(function($q, $injector) {
return {
response: function(response) {
if (response.config.nointercept) {
return $q.when(response); // let it pass
} else {
var defer = $q.defer();
$injector.invoke(function($http) {
// This modification prevents interception:
response.config.nointercept = true;
// Reuse modified config and send the same request again:
$http(response.config)
.then(function(resp) { defer.resolve(resp); },
function(resp) { defer.reject(resp); });
});
return defer.promise;
}
}
};
});
Having the testing for property in interceptor, you may prevent the interception in controllers and services:
app.controller('myController', function($http) {
// The second parameter is actually 'config', see API docs.
// This query will not be duplicated by the interceptor.
$http.get('/foo/bar', {nointercept: true})
.success(function(data) {
// ...
});
});

Answer 2

I used what is described in the answer but I used the syntax with a factory because with the anonymous function it didn't work, I don't really know why:
(function(angular){
angular.module('app', [])
.config([
'$httpProvider',
function($httpProvider) {
$httpProvider.interceptors.push('Interceptor');
}
])
.factory('Interceptor', [
'$injector',
InterceptorFactory
]);
function InterceptorFactory($injector){
return {
request: function(config) {
var ServiceWithHttp = $injector.get('ServiceWithHttp');
// Use ServiceWithHttp
return config;
}
};
}
}(window.angular));