在 Promise 链中调用异步方法时出现“TypeError：X 不是函数”答案

【问题标题】：Getting "TypeError: X is not a function" when calling async method in promises chain在 Promise 链中调用异步方法时出现“TypeError：X 不是函数”
【发布时间】：2019-08-25 07:47:12
【问题描述】：

我目前正在尝试创建一个从公共交通 API 获取信息的小应用。我创建了一些类来表示对象，其中一些（这里，Route）包含异步方法。我不知道如何正确调用它们并不断收到 TypeError。

这是我的测试脚本：

import { TagHelper } from './modules/TagHelper';

function testMod() {
    TagHelper.getRouteInfo("C1")
        .then(C1 => C1.loadPatterns())
        .then(C1 => C1.loadStops())
        .then(C1 => console.log(C1))
    ;
}

testMod();

这是我的辅助模块：

import requestPromise = require('request-promise');

class Route {
    readonly id: string;
    readonly shortName: string;
    readonly longName: string;
    readonly mode: string;
    readonly color: number;
    readonly agencyName: string;
    patterns: Pattern[];
    stops: Stop[];

    constructor(id: string, shortName: string, longName: string, mode: string, color: string, agencyName: string) {
        this.id = id;
        this.shortName = shortName;
        this.longName = longName;
        this.mode = mode;
        this.color = parseInt(color, 16);
        this.agencyName = agencyName;
    }

    async loadPatterns() {
        console.log("TEST");
        this.patterns = JSON.parse(await requestPromise("https://data.metromobilite.fr/otp/routers/default/index/routes/" + this.id + "/patterns"));
        return this;
    }

    async loadStops() {
        this.stops = JSON.parse(await requestPromise("https://data.metromobilite.fr/otp/routers/default/index/routes/" + this.id + "/stops"));
        return this;
    }
}

class Pattern {
    ...
}

class Stop {
    ...
}

const TagHelper = {

    getRouteInfo: async function(route_short_name: string, route_mode: string = null): Promise<Route> {
        const routes_data: Route[] = JSON.parse(await requestPromise("https://data.metromobilite.fr/otp/routers/default/index/routes"));
        for(let route of routes_data) {
            if (route.shortName.toUpperCase() === route_short_name.toUpperCase() && (route_mode === null || route_mode.toUpperCase() === route.mode.toLocaleUpperCase()))
                return route;
        }
        return null;
    }
};

export { TagHelper, Route, Pattern, Stop };

编辑：我刚刚意识到我没有包含错误，所以这里是：

(node:868) UnhandledPromiseRejectionWarning: TypeError: C1.loadPatterns is not a function
    at temp.ts:5:24

【问题讨论】：

routes_data 不是Route 的数组。您没有 Route 类的实例。

标签： node.js typescript promise

【解决方案1】：

原来我只是混淆了 JSON 对象和类实例。感谢 estus 指出这一点！

我通过修改 Route 类修复了我的错误：

class Route {
    ...
    patterns: Pattern[];
    stops: Stop[];

    constructor(id: string, shortName: string, longName: string, mode: string, color: string, agencyName: string) {
        ...
        this.patterns = [];
        this.stops = [];
    }

    async loadPatterns() {
        for (let pattern of JSON.parse(await requestPromise("https://data.metromobilite.fr/otp/routers/default/index/routes/" + this.id + "/patterns"))) {
            this.patterns.push(new Pattern(pattern.id, pattern.desc));
        }
        return this;
    }

    async loadStops() {
        for (let stop of JSON.parse(await requestPromise("https://data.metromobilite.fr/otp/routers/default/index/routes/" + this.id + "/stops"))) {
            this.stops.push(new Stop(stop.bind, stop.code, stop.name, stop.lat, stop.lon, stop.cluster));
        }
        return this;
    }
}

【讨论】：