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AngularJS: API: auto/service/$injector
$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);Injection Function Annotation
JavaScript does not have annotations, and annotations are needed for 依赖注入. The following are all valid ways of annotating function with injection arguments and are equivalent.
// inferred (only works if code not minified/obfuscated)
$injector.invoke(Function(serviceA){});
// annotated
Function explicit(serviceA) {};
explicit.$inject = ['serviceA'];
$injector.invoke(explicit);
// inline
$injector.invoke(['serviceA', Function(serviceA){}]);Inference
In JavaScript calling toString() on a function returns the function definition. The definition
can then be parsed and the function arguments can be extracted. 注意： This does not work with
minification, and obfuscation tools since these tools change the argument names.
$inject Annotation
By adding an $inject property onto a function the injection parameters can be specified.
Inline
As an array of injection names, where the last item in the array is the function to call.
用法
$injector();
方法
-
get(名称);Return an instance of the service.
参数
参数 类型 详述 name string The name of the instance to retrieve.
返回值
* The instance.
-
invoke(fn, [self], [locals]);Invoke the method and supply the method arguments from the
$injector.参数
参数 类型 详述 fn !Function The function to invoke. Function parameters are injected according to the $inject Annotation rules.
self (可选)Object The
thisfor the invoked method.locals (可选)Object Optional object. If preset then any argument names are read from this object first, before the
$injectoris consulted.返回值
* the value returned by the invoked
fnfunction. -
has(名称);Allows the user to query if the particular service exists.
参数
参数 类型 详述 Name string of the service to query.
返回值
boolean returns true if injector has given service.
-
instantiate(Type, [locals]);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.
参数
参数 类型 详述 Type Function Annotated constructor function.
locals (可选)Object Optional object. If preset then any argument names are read from this object first, before the
$injectoris consulted.返回值
Object new instance of
Type. -
annotate(fn);Returns an array of service names which the function is requesting for injection. This API is used by the injector to determine which services need to be injected into the function when the function is invoked. There are three ways in which the function can be annotated with the needed dependencies.
Argument names
The simplest form is to extract the dependencies from the arguments of the function. This is done by converting the function into a string using
toString()method and extracting the argument names.// Given Function MyController($scope, $route) { // ... } // Then expect(injector.annotate(MyController)).toEqual(['$scope', '$route']);This method does not work with code minification / obfuscation. For this reason the following annotation strategies are supported.
The
$injectpropertyIf a function has an
$injectproperty and its value is an array of strings, then the strings represent names of services to be injected into the function.// Given var MyController = Function(obfuscatedScope, obfuscatedRoute) { // ... } // Define function dependencies MyController['$inject'] = ['$scope', '$route']; // Then expect(injector.annotate(MyController)).toEqual(['$scope', '$route']);The array notation
It is often desirable to inline Injected functions and that's when setting the
$injectproperty is very inconvenient. In these situations using the array notation to specify the dependencies in a way that survives minification is a better choice:// We wish to write this (not minification / obfuscation safe) injector.invoke(Function($compile, $rootScope) { // ... }); // We are forced to write break inlining var tmpFn = Function(obfuscatedCompile, obfuscatedRootScope) { // ... }; tmpFn.$inject = ['$compile', '$rootScope']; injector.invoke(tmpFn); // 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']);参数
参数 类型 详述 fn function()Array.<(string|function())> Function for which dependent service names need to be retrieved as described above.
返回值
Array.<string> The names of the services which the function requires.