自定义 ViewResolver 和依赖注入

Question

我正在尝试创建自定义 ViewResolver class（扩展 angular 的内置 class）以使用定制服务（我正在从外部系统加载我的样式）。然而，我运行遇到了依赖注入系统和 ViewResolver 的问题。

我的系统设置如下：

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);
    }
}

但是在 MyViewResolver 中，this._styleService 还没有被注入，目前是 undefined。应该注意 MyStyleService 还依赖于另一个注入服务 SomeOtherService，因此我需要确保该提供程序也已定义并且可用于注入器。

我希望 bootstrap 将所有这些服务 "provided"，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替代版本。

作为参考，这是 angular 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

您可以尝试将 class 配置为 useFactory:

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

自定义 ViewResolver 和依赖注入

Custom ViewResolver and dependency injection

dependency-injection

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angular2-services