使用InversifyJS注入函数的最佳方法

Question

有一个正式配方可以使用InversifyJS注入一个函数。基本上，我们定义了一个助手函数，它将返回一个给定函数func的匆匆版本，并使用container.get(...)解析其所有依赖项。

import { container } from "./inversify.config"

function bindDependencies(func, dependencies) {
    let injections = dependencies.map((dependency) => {
        return container.get(dependency);
    });

    return func.bind(func, ...injections);
}

export { bindDependencies };

我们就这样用它：

import { bindDependencies } from "./utils/bindDependencies";
import { TYPES } from "./constants/types";

function testFunc(something, somethingElse) {
    console.log(`Injected! ${something}`);
    console.log(`Injected! ${somethingElse}`);
}

testFunc = bindDependencies(testFunc, [TYPES.something, TYPES.somethingElse]);

export { testFunc };

我想自动注入函数，而不显式地将它的依赖项提供给bindDependencies，可能是基于函数的参数名称。就像这样：

import { default as express, Router } from 'express';

import { bindDependencies } from '../injector/injector.utils';

import { AuthenticationMiddleware } from './authentication/authentication.middleware';
import { UsersMiddleware } from './users/users.middleware';

import { ENDPOINTS } from '../../../../common/endpoints/endpoints.constants';


function getRouter(
    authenticationMiddleware: AuthenticationMiddleware,
    usersMiddleware: UsersMiddleware,
): express.Router {
    const router: express.Router = Router();

    const requireAnonymity: express.Handler = authenticationMiddleware.requireAnonymity.bind(authenticationMiddleware);
    const requireAuthentication: express.Handler = authenticationMiddleware.requireAuthentication.bind(authenticationMiddleware);

    router.route(ENDPOINTS.AUTHENTICATION)
        .put(requireAnonymity, authenticationMiddleware.login.bind(authenticationMiddleware))
        .delete(requireAuthentication, authenticationMiddleware.logout.bind(authenticationMiddleware));

    router.route(ENDPOINTS.USER)
        .put(requireAnonymity, usersMiddleware.register.bind(usersMiddleware))
        .post(requireAuthentication, usersMiddleware.update.bind(usersMiddleware))
        .delete(requireAuthentication, usersMiddleware.remove.bind(usersMiddleware));

    return router;
}

const router: express.Router = invoke(getRouter);

export { router as Router };

注意，在这种情况下，我只想调用注入的函数一次，并得到它的返回值，这就是我要导出的，所以也许有一个更好的方法来完成这个任务，而不需要将代码包装在函数中，但是我认为直接在复合根之外使用container.get(...)并不是一个好主意，因为这个模块的依赖关系不清楚，并且可能分布在它的所有行中。此外，导出该函数将简化测试。

回到我的问题上，我的invoke函数如下所示：

function invoke<T>(fn: Function): T {
    const paramNames: string[] = getParamNames(fn);

    return fn.apply(null, paramNames.map((paramName: string)
        => container.get( (<any>container).map[paramName.toUpperCase()] ))) as T;
}

对于getParamNames，我使用这里提出的解决方案之一：如何从javascript动态获取函数参数名称/值

(<any>container).map是我在创建容器之后在inversify.config.ts中创建的一个对象，它链接了所有依赖项的键和真正的键的字符串表示形式，而不管它的类型(在本例中，只有symbol或Function)：

const container: Container = new Container();

container.bind<FooClass>(FooClass).toSelf();

...

const map: ObjectOf<any> = {};

(<any>container)._bindingDictionary._map
    .forEach((value: any, key: Function | symbol) => {
        map[(typeof key === 'symbol'
            ? Symbol.keyFor(key) : key.name).toUpperCase()] = key;
    });

(<any>container).map = map;

有人知道是否有更好的方法来做这件事，或者有什么重要的理由不去做？

Answer 1

使用函数参数名称的主要问题是压缩代码时可能出现的问题：

function test(foo, bar) {
    console.log(foo, bar);
}

变成：

function test(a,b){console.log(a,b)}

，因为您在Node.js应用程序中工作，所以您可能没有使用压缩，所以这对您的来说不应该是个问题。

我认为你的解决方案是一个很好的时间解决方案。如果您查看TypeScript地图，在“未来”一节中我们可以看到：

• 函数表达式/箭头函数的装饰器

这意味着今后InversifyJS将允许您执行以下操作：

注意:假设AuthenticationMiddleware和UsersMiddleware是类。

@injectable()
function getRouter(
    authenticationMiddleware: AuthenticationMiddleware,
    usersMiddleware: UsersMiddleware,
): express.Router {
    const router: express.Router = Router();

    const requireAnonymity: express.Handler = authenticationMiddleware.requireAnonymity.bind(authenticationMiddleware);
    const requireAuthentication: express.Handler = authenticationMiddleware.requireAuthentication.bind(authenticationMiddleware);

    router.route(ENDPOINTS.AUTHENTICATION)
        .put(requireAnonymity, authenticationMiddleware.login.bind(authenticationMiddleware))
        .delete(requireAuthentication, authenticationMiddleware.logout.bind(authenticationMiddleware));

    router.route(ENDPOINTS.USER)
        .put(requireAnonymity, usersMiddleware.register.bind(usersMiddleware))
        .post(requireAuthentication, usersMiddleware.update.bind(usersMiddleware))
        .delete(requireAuthentication, usersMiddleware.remove.bind(usersMiddleware));

    return router;
}

或如下：

注意:假设AuthenticationMiddleware和UsersMiddleware是接口。

@injectable()
function getRouter(
    @inject("AuthenticationMiddleware") authenticationMiddleware: AuthenticationMiddleware,
    @inject("UsersMiddleware") usersMiddleware: UsersMiddleware,
): express.Router {
    const router: express.Router = Router();

    const requireAnonymity: express.Handler = authenticationMiddleware.requireAnonymity.bind(authenticationMiddleware);
    const requireAuthentication: express.Handler = authenticationMiddleware.requireAuthentication.bind(authenticationMiddleware);

    router.route(ENDPOINTS.AUTHENTICATION)
        .put(requireAnonymity, authenticationMiddleware.login.bind(authenticationMiddleware))
        .delete(requireAuthentication, authenticationMiddleware.logout.bind(authenticationMiddleware));

    router.route(ENDPOINTS.USER)
        .put(requireAnonymity, usersMiddleware.register.bind(usersMiddleware))
        .post(requireAuthentication, usersMiddleware.update.bind(usersMiddleware))
        .delete(requireAuthentication, usersMiddleware.remove.bind(usersMiddleware));

    return router;
}