Question

我正在查看async库，但我似乎无法找到处理管道的控制流程。我只是想知道我在这里是否遗漏了什么。

我想实现一个管道。例如：

let pipeline = [];
pipeline.push((input, next) => { next(null, input); });
pipeline.push((input, next) => { next(null, input); });
var pipelineResult = pipelineRunner.run(pipeline, 'sample input', (error, result) => {});

说明：调用一系列函数。每个函数都会收到input和next函数。每个函数处理input并将其作为参数传递给next函数。作为管道执行的结果，我获得了已处理的input，或者，如果任何函数调用next并出现错误，则管道停止并调用回调。

我想这是一个非常常见的用例，所以我认为async可以做到，但我无法找到它。如果您知道任何其他可以实现此类结果的库，那也是可以接受的。

Answer 1

您正在寻找async.waterfall function。

如果您需要一个可以将初始input传递给的函数，则可以apply asyc.seq或async.compose使用多个参数。

Answer 2

我最终自己实现了它，尽管如@Bergi所示，/** * Runs asynchronous pipelines */ class PipelineRunner { /** * Runs the given pipeline * @param pipeline - The array of functions that should be executed (middleware) * @param middlewareArgs - The array of arguments that should be passed in to the middleware * @param input * @param next */ run(pipeline, middlewareArgs, input, next) { if (!pipeline) throw Error('\'pipeline\' should be truthy'); if (!context) throw Error('\'context\' should be truthy'); if (!input) throw Error('\'input\' should be truthy'); if (!next) throw Error('\'next\' should be truthy'); if (!pipeline.length) throw Error('\'pipeline.length\' should be truthy'); let index = 0; // the link function "binds" every function in the pipeline array together let link = (error, result) => { if (error) { next(error); return; } let nextIndex = index++; if (nextIndex < pipeline.length) { let args = [result].concat(middlewareArgs).concat(link); pipeline[nextIndex].apply(null, args); } else { next(null, result); } }; let args = [input].concat(middlewareArgs).concat(link); pipeline[index++].apply(null, args); } } export default new PipelineRunner();确实支持它。

import chai from 'chai';
import pipelineRunner from '../src/server/lib/pipelines/pipelineRunner';
let assert = chai.assert;


describe('PipelineRunner', () => {
    describe('run', function() {
        it('Happy path', () => {
            let pipeline = [];
            pipeline.push((input, next) => { next(null, input); });
            pipeline.push((input, next) => { next(null, input); });

            pipelineRunner.run(pipeline, [], 'happy', (error, result) => {
                assert.strictEqual(result, "happy");
            });
        });

        it('Happy path - with arguments', () => {
            let pipeline = [];
            pipeline.push((input, someArgument, next) => {
                assert.strictEqual(someArgument, 'something that should be passed in');
                next(null, input);
            });
            pipeline.push((input, someArgument, next) => { next(null, input); });

            pipelineRunner.run(pipeline, ['something that should be passed in'], 'happy', (error, result) => {
                assert.strictEqual(result, "happy");
            });
        });

        it('When something goes wrong', () => {
            let pipeline = [];
            pipeline.push((input, next) => { next(null, input); });
            pipeline.push((input, next) => { next('something went wrong'); });

            pipelineRunner.run(pipeline, [], 'happy', (error, result) => {
                assert.strictEqual(error, 'something went wrong');
            });
        });
    });
});

单元测试：

Collections.sort(Comparator<? super Customer>...)

异步库是否有任何用于处理管道的控制流？

2 个答案: