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具有已定义类型的函数库

typescript

ThomasReggi · 技术社区 · 5 年前

我试图以一种方式组合函数,在这种方式中,我可以定义名称、输入和返回类型,然后从中心函数访问它们。但是,当我这样做时,我会丢失输入信息。

如果没有硬编码的值类型,如何构建这样的系统?

import * as fs from 'fs';
import { promisify } from 'util';
import * as lodash from 'lodash';

const libs = []

export enum Types {
    number,
    numbers,
    string,
    buffer,
}

export enum Actions {
    add,
    subtract,
    readFile,
}

libs.push({
    action: Actions.add,
    from: Types.numbers,
    get: Types.number,
    fn: (...n: number[]): number => n.reduce((a, b) => a + b, 0),
})

libs.push({
    action: Actions.subtract,
    from: Types.numbers,
    get: Types.number,
    fn: (...n: number[]): number => n.reduce((a, b) => a - b, 0),
})

libs.push({
    action: Actions.readFile,
    from: Types.string,
    get: Types.string,
    fn: async (s:string): Promise<string> => promisify(fs.readFile)(s, 'UTF8'),
})

libs.push({
    action: Actions.readFile,
    from: Types.string,
    get: Types.buffer,
    fn: async (s:string): Promise<Buffer> => promisify(fs.readFile)(s),
})

const library = (a: Actions, from: Types, get: Types, lib) => {
    const found = lodash.find(lib, fn => {
        return (
        lodash.isEqual(fn.from, from) &&
        lodash.isEqual(fn.get, get)
        );
    });
    if (!found) throw new Error('no conversion');
    return found.fn;
}

const { readFile } = Actions;
const { string: s } = Types;

const x = library(readFile, s, s, libs)

x('./tres.ts').then(console.log)

我如何保留的输入信息 x

1 回复 | 直到 5 年前

Titian Cernicova-Dragomir 5 年前

我们需要保护自己 libs 数组中实际项的类型。最简单的方法是借助一个额外的函数来推断 自由基 基于数组中的实际项(包括where的文本类型 Actions 和 Types

根据这些信息,我们可以键入 library 要从中提取函数类型的函数 自由基 那是一样的 action , get 和 from 作为传入类型:

import * as fs from 'fs';
import { promisify } from 'util';
import * as lodash from 'lodash';


export enum Types {
    number,
    numbers,
    string,
    buffer,
}

export enum Actions {
    add,
    subtract,
    readFile,
}

function makeLib<T extends Array<{action : A, from: F, get: G, fn: (...a: any[])=> any}>, A extends Actions, F extends Types, G extends Types>(...a:T){
    return a;
}
const libs = makeLib({
    action: Actions.add,
    from: Types.numbers,
    get: Types.number,
    fn: (...n: number[]): number => n.reduce((a, b) => a + b, 0),
}, {
    action: Actions.subtract,
    from: Types.numbers,
    get: Types.number,
    fn: (...n: number[]): number => n.reduce((a, b) => a - b, 0),
}, {
    action: Actions.readFile,
    from: Types.string,
    get: Types.string,
    fn: async (s:string): Promise<string> => promisify(fs.readFile)(s, 'UTF8'),
}, {
    action: Actions.readFile,
    from: Types.string,
    get: Types.buffer,
    fn: async (s:string): Promise<Buffer> => promisify(fs.readFile)(s),
})

const library = <T extends Array<{action : Actions, from: Types, get: Types, fn: (...a: any[])=> any}>, A extends Actions, F extends Types, G extends Types>(a: A, from: F, get: G, lib: T) => {
    const found = lodash.find(lib, fn => {
        return (
        lodash.isEqual(fn.from, from) &&
        lodash.isEqual(fn.get, get)
        );
    });
    if (!found) throw new Error('no conversion');
    return found.fn as Extract<T[number], {action : A, from: F, get: G }>['fn'];
}

const { readFile } = Actions;
const { string: s } = Types;

const x = library(readFile, s, s, libs) // x is (s: string) => Promise<string

x('./tres.ts').then(console.log)

const x2 = library(Actions.subtract, Types.string, Types.string, libs)  // never
const x3 = library(Actions.subtract, Types.numbers, Types.number, libs)  //  (...n: number[]) => number

strings 而不是枚举:

function makeLib<T extends Array<{action : V, from: V, get: V, fn: (...a: any[])=> any}>, V extends string>(...a:T){
    return a;
}
const libs = makeLib({
    action: "add",
    from: "numbers",
    get: "number",
    fn: (...n: number[]): number => n.reduce((a, b) => a + b, 0),
}, {
    action: "subtract",
    from: "numbers",
    get: "number",
    fn: (...n: number[]): number | null => n.reduce((a, b) => a - b, 0),
}, {
    action: "readFile",
    from: "string",
    get: "string",
    fn: async (s:string): Promise<string> => promisify(fs.readFile)(s, 'UTF8'),
}, {
    action: "readFile",
    from: "string",
    get: "buffer",
    fn: async (s:string): Promise<Buffer> => promisify(fs.readFile)(s),
})

const library = <T extends Array<{action : string, from: string, get: string, fn: (...a: any[])=> any}>, 
    A extends T[number]['action'], F extends T[number]['from'], G extends T[number]['get']>(a: A, from: F, get: G, lib: T) => {
    const found = lodash.find(lib, fn => {
        return (
        lodash.isEqual(fn.from, from) &&
        lodash.isEqual(fn.get, get)
        );
    });
    if (!found) throw new Error('no conversion');
    return found.fn as Extract<T[number], {action : A, from: F, get: G }>['fn'];
}

const { readFile } = Actions;
const { string: s } = Types;

const x = library("readFile", "string", "string", libs) // x is (s: string) => Promise<string

x('./tres.ts').then(console.log)

const x2 = library("subtract", "string", "string", libs)  // never
const x3 = library("subtract", "numbers", "number", libs)  //  (...n: number[]) => number