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# Error: error:unpr
Unknown Provider

    Unknown provider: {0}

## Description

This error results from the `$injector` being unable to resolve a required dependency. To fix this, make sure the dependency is defined and spelled correctly. For example:

    angular.module('myApp', [])
    .controller('MyController', ['myService', function (myService) {
      // Do something with myService
    }]);

The above code will fail with `$injector:unpr` if `myService` is not defined.

Making sure each dependency is defined will fix the problem, as noted below.

    angular.module('myApp', [])
    .service('myService', function () { /* ... */ })
    .controller('MyController', ['myService', function (myService) {
      // Do something with myService
    }]);

An unknown provider error can also be caused by accidentally redefining a module using the `angular.module` API, as shown in the following example.

    angular.module('myModule', [])
    .service('myCoolService', function () { /* ... */ });

    angular.module('myModule', [])
    // myModule has already been created! This is not what you want!
    .directive('myDirective', ['myCoolService', function (myCoolService) {
      // This directive definition throws unknown provider, because myCoolService
      // has been destroyed.
    }]);

To fix this problem, make sure you only define each module with the `angular.module(name, [requires])` syntax once across your entire project. Retrieve it for subsequent use with `angular.module(name)`. The fixed example is shown below.

    angular.module('myModule', [])
    .service('myCoolService', function () { /* ... */ });

    angular.module('myModule')
    .directive('myDirective', ['myCoolService', function (myCoolService) {
      // This directive definition does not throw unknown provider.
    }]);

Attempting to inject one controller into another will also throw an `Unknown provider` error:

    angular.module('myModule', [])
    .controller('MyFirstController', function() { /* ... */ });
    .controller('MySecondController', ['MyFirstController', function(MyFirstController) {
      // This controller throws an unknown provider error because
      // MyFirstController cannot be injected.
    }]);

Use the `$controller` service if you want to instantiate controllers yourself.