如何使用 Inject 获取一次服务实例

Question

如何使用 Injector 获得相同的一次单例服务实例：

我在 bootstrap 应用程序上定义了此服务的提供者（对于所有应用程序的一个实例）

示例：

Bootstrap申请

//Init application
bootstrap(AppComponent, [ROUTER_PROVIDERS, HTTP_PROVIDERS, SessionService]);

会话服务

单例 - 这只是示例，但实际上可以是会话或 acl 服务

@Injectable()
export class SessionService {
    constructor() {
        console.warn("INSTANCE OF SESSION SERVICE-a");
    }
    public getInstance(instanceName: string){
        console.warn("Injected service come from component name: " + instanceName);
    }
}

SecuredHomeComponent

当我在构造函数上注入服务时，只有一次服务实例（好）

@Component()
@CanActivate(AccessService.checkSession)
export class SecuredHomeComponent {
    public constructor(private testSessionService: SessionService) {
        this.testSessionService.getInstance('Component1:1'); //Test 1 - get the same instance when service is inject into contructor
    }
}

MyStaticService

我这样尝试，注入服务但总是得到新的服务实例但是我需要使用 "Injector.resolveAndCreate" 直接注入例如静态方法，然后 NG2 创建新的服务实例 (bad)

@Injectable()
export class MyStaticService {
    public static getDataFromService() {
        //That two ways is bad, bcs create new instance of my test SessionService
        //Test4
        let providers = Injector.resolve([ SessionService ]);
        let injectorFirst = Injector.fromResolvedProviders(providers);
        let testServFirst = injectorFirst.get(SessionService);
        testServFirst.getInstance('StaticService1:1');
        //Test 5
        let injectorSecond = Injector.resolveAndCreate([SessionService]);
        let testServSecond = injectorSecond.get(SessionService);
        testServSecond.getInstance('StaticService1:2');
    }
}

静态服务

对于真实示例，我需要使用静态方法的静态 class 如果我很好地理解文档，当想要覆盖注释的方法时 canActivate 必须提供带有静态方法的服务

行：我的"SecuredHomeComponent"

中的@CanActivate(AccessService.checkSession)

//Static Service - ACCESS
@Injectable()
export class AccessService {
    public static checkAccess = (next: ComponentInstruction, prev: ComponentInstruction): boolean => {        
        return AccessService.checkSession() && AccessService.checkAcl(res, priv);
    }
    public static checkSession(): boolean {
        let injectedSessionServices: SessionService; //How to inject the same instance of my SessionService?
        return injectedSessionServices.getDataFromService(); //for real service he get back checkSession from sessionService
    }
    public static checkAcl(aclResource: AclResources, aclPrivilege: AclPrivileges): boolean {
        let injectedAclServices: SessionService; //How to inject the same instance of my SessionService?
        return injectedAclServices.checkAcl(aclResource, aclPrivilege);
    }
}

Answer 1

Angulars DI 为每个提供者保留一个实例。如果从同一个提供者请求一个实例，则每次都返回同一个实例。

你可以做的是，提供一个工厂并调用工厂来获取新的实例。

bootstrap(AppComponent, [provide(CommonTestService, {useFactory: () => {
  return () => {
    new CommonTestService();
  }
})]);

如果服务本身有依赖项（构造函数参数），那么您也需要提供它们

bootstrap(AppComponent, [MyServiceDependency, provide(CommonTestService, {useFactory: () => {
  return () => {
    new CommonTestService(dep);
  },
  deps: [MyServiceDependency]
})]);

那你就可以像这样使用了

@Component()
export class HomeComponent {
  public constructor(@Inject(CommonTestService) private testService:any) {
    let s1 = testService(); // new instance
    let s2 = testService(); // new instance
    ..
  }
}

Answer 2

我找到了使用一个全局服务实例的解决方案 injector 实现了标准单例 class getInstance() 到 bootstrap申请。然后可以在所有级别的应用程序上获得注入服务的简单实例。如果有时间有人找到不同的解决方案，或者 NG2 解决了这个不同的问题，请告诉我。

非常简单的示例代码：

Bootstrap 应用

//Init application
bootstrap(AppComponent, [ROUTER_PROVIDERS, MY_PROVIDERS, HTTP_PROVIDERS])
    .then((appRef) => MainInjectorService.getInstance().setInjector(appRef.injector));

我的帮手主喷油器

import { Injector, Injectable } from 'angular2/src/core/di';

@Injectable()
export class MainInjectorService
{
    static instance:MainInjectorService;    
    static isCreating:Boolean = false;
    private _injector: Injector;

    constructor() {
        if (!MainInjectorService.isCreating) {
            throw new Error("You can't call new in Singleton instances!");
        }
    }

    public static getInstance() {
        if (MainInjectorService.instance == null) {
            MainInjectorService.isCreating = true;
            MainInjectorService.instance = new MainInjectorService();
            MainInjectorService.isCreating = false;
        }

        return MainInjectorService.instance;
    }

    public setInjector(injector: Injector) {
        this._injector = injector;
    }

    public getInjector(): Injector {
        return this._injector;
    }
}

我的静态 class

// Access - static service 
@Injectable()
export class StaticAccessService {

    // Get service instance from global provides service
    private static _getService<T>(serviceName: any) {
        let injector: Injector = MainInjectorService.getInstance().getInjector();
        return injector.get(serviceName);
    }

    //Check access to session and acl
    public static checkAccess = (next: ComponentInstruction, prev: ComponentInstruction): boolean => {
        return StaticAccessService.checkSession() && StaticAccessService.checkAcl(next.routeData.data['res'], next.routeData.data['priv']);
    }

    // Check session access
    public static checkSession(): boolean {
        return StaticAccessService._getService(MySessionService).checkSession();
    }

    // Check session access
    public static checkAccess(res, priv): boolean {
        return StaticAccessService._getService(MyAclService).checkAccess(res, priv);
    }
}

以及如何在组件中使用

@Component()
@CanActivate(StaticAccessService.checkAccess)
export class SecuredComponent {
}

如何使用 Inject 获取一次服务实例

How to get once instance of service with Inject

angular2-services

angular

Bootstrap申请

会话服务

SecuredHomeComponent

MyStaticService

静态服务