$injector
(service in module AUTO
)
$injector is used to retrieve object instances as defined by
provider, instantiate types, invoke methods,
and load modules.
The following always holds true:
var $injector = angular.injector();
expect($injector.get('$injector')).toBe($injector);
expect($injector.invoke(function($injector){
return $injector;
}).toBe($injector);
JavaScript does not have annotations, and annotations are needed for dependency injection. The following ways are all valid way of annotating function with injection arguments and are equivalent.
// inferred (only works if code not minified/obfuscated)
$inject.invoke(function(serviceA){});
// annotated
function explicit(serviceA) {};
explicit.$inject = ['serviceA'];
$inject.invoke(explicit);
// inline
$inject.invoke(['serviceA', function(serviceA){}]);
In JavaScript calling toString() on a function returns the function definition. The definition can then be
parsed and the function arguments can be extracted. NOTE: This does not work with minification, and obfuscation
tools since these tools change the argument names.
$inject AnnotationBy adding a $inject property onto a function the injection parameters can be specified.
As an array of injection names, where the last item in the array is the function to call.
Returns an array of service names which the function is requesting for injection. This API is used by the injector to determine which services need to be injected into the function when the function is invoked. There are three ways in which the function can be annotated with the needed dependencies.
The simplest form is to extract the dependencies from the arguments of the function. This is done by converting
the function into a string using toString() method and extracting the argument names.
// Given
function MyController($scope, $route) {
// ...
}
// Then
expect(injector.annotate(MyController)).toEqual(['$scope', '$route']);
This method does not work with code minfication / obfuscation. For this reason the following annotation strategies are supported.
$injector propertyIf a function has an $inject property and its value is an array of strings, then the strings represent names of
services to be injected into the function.
// Given
var MyController = function(obfuscatedScope, obfuscatedRoute) {
// ...
}
// Define function dependencies
MyController.$inject = ['$scope', '$route'];
// Then
expect(injector.annotate(MyController)).toEqual(['$scope', '$route']);
It is often desirable to inline Injected functions and that's when setting the $inject property is very
inconvenient. In these situations using the array notation to specify the dependencies in a way that survives
minification is a better choice:
// We wish to write this (not minification / obfuscation safe)
injector.invoke(function($compile, $rootScope) {
// ...
});
// We are forced to write break inlining
var tmpFn = function(obfuscatedCompile, obfuscatedRootScope) {
// ...
};
tmpFn.$inject = ['$compile', '$rootScope'];
injector.invoke(tempFn);
// To better support inline function the inline annotation is supported
injector.invoke(['$compile', '$rootScope', function(obfCompile, obfRootScope) {
// ...
}]);
// Therefore
expect(injector.annotate(
['$compile', '$rootScope', function(obfus_$compile, obfus_$rootScope) {}])
).toEqual(['$compile', '$rootScope']);
fn – {function|Array.<string|Function>} –
Function for which dependent service names need to be retrieved as described above.
{Array.<string>}
– The names of the services which the function requires.
Return an instance of the service.
name – {string} –
The name of the instance to retrieve.
{*}
– The instance.
Create a new instance of JS type. The method takes a constructor function invokes the new operator and supplies all of the arguments to the constructor function as specified by the constructor annotation.
Type – {function} –
Annotated constructor function.
locals(optional) – {Object=} –
Optional object. If preset then any argument names are read from this object first, before
the $injector is consulted.
{Object}
– new instance of Type.
Invoke the method and supply the method arguments from the $injector.
fn – {!function} –
The function to invoke. The function arguments come form the function annotation.
self(optional) – {Object=} –
The this for the invoked method.
locals(optional) – {Object=} –
Optional object. If preset then any argument names are read from this object first, before
the $injector is consulted.
{*}
– the value returned by the invoked fn function.