angularjs $provide service

Eyal VardiCEO E4D Solutions LTDMicrosoft MVP Visual

C#blog: www.eVardi.com

$provide Services

Agenda

AngularJS Service Overview

$provide functions:

Provider

Factory

Service

Value & Constant

Decorator

Angular Services Angular services are singletons

that carry out specific tasks.

All services in Angular are instantiated lazily.

There are three functions for creating generic services, with different levels of complexity and ability:

Service

Factory

Provider

Registering Services You can register the service with the module either via the

Module api or by using the $provide service in the module configuration function.

var myModule = angular.module('myModule', []);myModule.factory('serviceId', function () { var shinyNewServiceInstance; //factory function body that constructs shinyNewServiceInstance return shinyNewServiceInstance;});

angular.module('myModule', [], function ($provide) { $provide.factory('serviceId', function () { var shinyNewServiceInstance; //factory function body that constructs shinyNewServiceInstance return shinyNewServiceInstance; });});

Option I

Option II

$provide functions for creating generic services

service(name, constructor) you will be provided the actual function

reference passed to module.service.

factory(name, $getFn) you will be provided the value that is returned by invoking

the function reference passed to module.factory.

provider(name, provider) you will be provided the value that is returned by invoking

the $get method of the function reference passed to module.provider.

Provider Functionangular.module('myApp', [])

.provider('myPro', function() {

    console.log('myApp => Create provider => retrun object with $get

');

    return {         

isTrue: false,         

$get: function b($http) {             

var self = this;             

console.log('myApp => my Provider $get => retrun func');

      return function c(msg) {

console.log(msg + " isTrue: " + self.isTrue);

     };

        }

    };

});

Step 1: Invoke the function before the config stage. No args.

app.config(function (myProProvider) {               myProProvider.isTrue = true;               console.log('myApp --> config');});

Step 2: This object will be available in config stage as injectable service. The name is "myProProvider".

Step 3: $get func is a factory func for the service, invoke only if needed and only once. Available after the config stage.

Step 4: The injectable service.

Provider Service

Angular Provider Function Codefunction provider(name, provider_) {

if (isFunction(provider_) || isArray(provider_)) { provider_ = providerInjector.instantiate(provider_); }

if (!provider_.$get) { throw Error(...'must define $get factory method.'); }

return providerCache[name + providerSuffix] = provider_;}

// Register an object providermyApp.provider('awesome', { $get: function () { return 'awesome data'; }});

Step 1: Invoke the function before the config stage. No args.

Step 2: This object will be available in config stage as injectable service. The name is "[name + providerSuffix]".

Factory Function

angular.module('myApp', [])

  .factory('myfac', function ($http) {

      console.log('myApp -> Create factory');

      return function (msg) {

         console.log(msg);

      };

});

Step 2: The injectable service.

Step 1: factory func for the service, invoke only if needed and only once. Available after the config stage.

app.run(function ( myfac ){     console.log('myApp --> run');     myfac("test"); });

Angular Factory Function Codefunction factory(name, factoryFn) { return provider(name, { $get: factoryFn });}

// Sample Code

angular.module('myApp', [])

  .factory('myfac', function ($http) {

      console.log('myApp -> Create factory');

      return function (msg) {

         console.log(msg);

      };

});

Angular Factory Is Provider

function factory(name, factoryFn) { return provider(name, { $get: factoryFn });}

// Sample Code

angular.module('myApp', [])

  .provider('myfac', { $get : function ($http) {

      console.log('myApp -

> Create factory');

      return function (msg) {

         console.log(msg);

      };

}

}

);

Service Function

function MyService($http) {

    console.log('Create my Service => retrun object this.');

    this.msg = 'NAN';

}

MyService.prototype.log = function (val) {

    console.log(this.msg + val );

};

angular.module('myApp', []).service( 'myService', MyService );

Angular use the new operator to create

instance.

The return object (this) is the singleton

service.

Everything that uses the service will get the

same instance!

Angular Service Function Codefunction service(name, constructor) {

return factory(name, ['$injector', function ($injector) {

// instantiated with the new operator

return $injector.instantiate(constructor);

}]);

} Angular use the new operator to create

instance.

The return object (this) is the singleton

service.

Everything that uses the service will get the

same instance!

Angular Service Is Provider

function service(name, constructor) {

return provider(name, {

$get: ['$injector', function ($injector) {

// instantiated with the new operator

return

$injector.instantiate(constructor);

}]

});

}

Angular use the new operator to create

instance.

The return object (this) is the singleton

service.

Everything that uses the service will get the

same instance!

Value Function

function value(name, value) { return factory(name, valueFn(value));}

// Sample CodemyApp.value('awesome', 'awesome data');

function valueFn(value) {return function() {return value;};}

// Sample Code

angular.module('myApp', [])

.constant('PI', 3.14)

.config(function (PI)

{ ... });

Constant Function Constant differs from value in that it's

accessible during config.

Constant cannot be overridden by an Angular decorator.

// AngularJS Constant Codefunction constant(name, value) { providerCache[name] = value; instanceCache[name] = value;}

Angular $provide (Custom Service)

Decorator Function A service decorator intercepts the

creation of a service, allowing it to override or modify the behavior of the service.

Here we decorate the $log service to convert warnings to errors by intercepting calls to $log.warn(). $provider.decorator('$log', ['$delegate', function ($delegate) {

    $delegate.warn = $delegate.error;

    return $delegate;

}]);

$log

Angular Decorator Code

function decorator(serviceName, decorFn) {

    var origProvider = providerInjector.get(serviceName + providerSuffix),

        orig$get  = origProvider.$get;

    origProvider.$get = function() {

      var origInstance = instanceInjector.invoke(orig$get, origProvider);

      return instanceInjector.invoke(

decorFn, null, { $delegate: origInstance }

);

    };

  }

Override the $get function.

Invoke the decoFn with original service instance as argument.

Decorator

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Eyal VardiCEO E4D Solutions LTDMicrosoft MVP Visual C#blog: www.e4d.co.il