自定义ViewResolver和依赖项注入

Question

我试图创建一个自定义ViewResolver类（扩展角度的内置类）以增强我的系统样式元数据与自定义服务（我从外部系统加载我的样式）。但是，我遇到了依赖注入系统和ViewResolver的问题。

我有我的系统设置类似如下：

Boot.ts：

bootstrap(App, [ 
    MyStyleService, // my custom service 
    SomeOtherService, // another custom service used by MyStyleService 
    { 
     provide: ViewResolver, 
     useClass: MyViewResolver // my custom ViewResolver 
    } 
]) 

MyViewResolver.ts：

@Injectable() 
export class MyViewResolover extends ViewResolver { 

    constructor(
     private _reflector: ReflectorReader, 
     // I want to reference 'StyleService' from the providers array in boot.ts 
     private _styleService: StyleService 
    ) { 
     super(_reflector); 
    } 

    public resolve(comopnent: Type) { 
     let meta: ViewMetadata = super.resolve(component); 

     let styles = this._styleService.someMethod(meta); 
    } 
} 

然而在MyViewResolver里面，this._styleService还没有被注入，现在是undefined。应该注意的是，MyStyleService也取决于另一个注入服务SomeOtherService，所以我需要确保该提供者也被定义并可用于注入器。

我希望所有这些服务都由bootstrap“提供”，以便将来我可以在每个系统的基础上提供我的任何服务的备用版本。

供参考，这是角的核心ViewResolver：

view_resolver.ts（Angular2核心）：

import {Injectable, ViewMetadata, ComponentMetadata,} from '@angular/core'; 
import {ReflectorReader, reflector} from '../core_private'; 
import {Type, stringify, isBlank, isPresent} from '../src/facade/lang'; 
import {BaseException} from '../src/facade/exceptions'; 
import {Map} from '../src/facade/collection'; 

@Injectable() 
export class ViewResolver { 
    constructor(private _reflector: ReflectorReader = reflector) {} 

    resolve(component: Type): ViewMetadata { 
     ... stuff here ... 
    } 
} 

Answer 1

你可以尝试用useFactory配置类：

bootstrap(App, [ 
    MyStyleService, 
    SomeOtherService, 
    { 
    provide: ViewResolver, 
    useFactory: (_reflector: ReflectorReader, styleService: StyleService) => { 
     return MyViewResolver(_reflector, _styleService); 
    }, 
    deps: [ ReflectorReader, StyleService ] 
    } 
]);