角度依赖注入到导出函数中 [英] Angular dependency injection into an export function

问题描述

我正在使用apollo graphql，它具有一个内部带有功能的模块.

I am using apollo graphql, and it has a module with a function inside of it.

export function createApollo(httpLink: HttpLink, connectToDevTools: true){

在此函数中，您可以定义graphql端点的网址 const uri = http://127.0.0.1/graphql .

Inside this function you define the url for the graphql endpoint const uri = http://127.0.0.1/graphql for instance.

我想将此URL从服务导入(这样，我只需要在一个地方更改后端服务器URL)，但由于属性仍未定义，因此我无法注入该服务.

I would like to import this url form a service (so that I only have to change the backend server url in one place), but I can not inject the service, for the property stays undefined.

export function createApollo(httpLink: HttpLink, connectToDevTools: true, urlservice: UrlsService) {
    const uri = urlservice.graphqlAddress;

错误:无法读取未定义的属性'graphqlAddress'

我也尝试过将服务注入模块构造函数中，但这甚至在链的下游，具有相同的结果.

I have also tried injecting the service into the modules constructor, but this is even lower down the chain, with the same results.

如何将外部属性添加到函数 createApollo 中?

How do I get an outside property into the function createApollo?

我的服务基本上是这样的:

My service basically looks like this:

export class UrlsService {
    ...
    graphqlAddress = 'http://192.168.2.24:8000/graphql/';
    ...
}

GraphQLModule提供程序:

GraphQLModule providers:

@NgModule({
    exports: [ApolloModule, HttpLinkModule],
    providers: [
        UrlsService,
        {
            provide: APOLLO_OPTIONS,
            useFactory: createApollo,
            deps: [HttpLink],
        },
    ],
})
export class GraphQLModule {
}

推荐答案

在声明带有参数的工厂函数时，需要在提供程序配置的依赖项设置 deps 中声明这些参数.(这在角度文档中进行了说明).因此，在您的示例中，您需要添加 UrlsService

When declaring a factory function that takes parameters, you need to declare these parameters in the dependency setting deps , in the providers config. (This is explained in the angular doc). So in your example, you need to add UrlsService

@NgModule({
    exports: [ApolloModule, HttpLinkModule],
    providers: [
        UrlsService,
        {
            provide: APOLLO_OPTIONS,
            useFactory: createApollo,
            deps: [HttpLink, UrlsService],
        },
    ],
})
export class GraphQLModule {
}

此外， connectDevTools 参数看起来好像没有正确声明

Also, the connectDevTools argument does not look like it's declared properly

export function createApollo(httpLink: HttpLink, connectToDevTools: true, urlservice: UrlsService) 

这篇关于角度依赖注入到导出函数中的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！