TypeError：类扩展值undefined不是函数或null [英] TypeError: Class extends value undefined is not a function or null

问题描述

尝试创建这些实体时出现以下错误。

I am getting the following error when trying to create these entities.

TypeError：类扩展值undefined不是函数或null

我假设这与循环依赖有关，但是当使用表继承和一对多关系时应该如何避免这种情况？

I am assuming this has something to do with circular dependencies, but how is that supposed to be avoided when using table inheritance and one to many relationships?

在 BaseComic_1.BaseComic 中抱怨以下javascript。

It is complaining about the following javascript at BaseComic_1.BaseComic.

让Variant = class Variant扩展BaseComic_1.BaseComic {

let Variant = class Variant extends BaseComic_1.BaseComic {

这是完整的文件。

"use strict";
var __decorate = (this && this.__decorate) || function (decorators, target, key, desc) {
    var c = arguments.length, r = c < 3 ? target : desc === null ? desc = Object.getOwnPropertyDescriptor(target, key) : desc, d;
    if (typeof Reflect === "object" && typeof Reflect.decorate === "function") r = Reflect.decorate(decorators, target, key, desc);
    else for (var i = decorators.length - 1; i >= 0; i--) if (d = decorators[i]) r = (c < 3 ? d(r) : c > 3 ? d(target, key, r) : d(target, key)) || r;
    return c > 3 && r && Object.defineProperty(target, key, r), r;
};
var __metadata = (this && this.__metadata) || function (k, v) {
    if (typeof Reflect === "object" && typeof Reflect.metadata === "function") return Reflect.metadata(k, v);
};
Object.defineProperty(exports, "__esModule", { value: true });
const typeorm_1 = require("typeorm");
const Comic_1 = require("./Comic");
const BaseComic_1 = require("./BaseComic");
let Variant = class Variant extends BaseComic_1.BaseComic {
};
__decorate([
    typeorm_1.ManyToOne(type => Comic_1.Comic, comic => comic.variants),
    __metadata("design:type", Comic_1.Comic)
], Variant.prototype, "comic", void 0);
Variant = __decorate([
    typeorm_1.ClassEntityChild()
], Variant);
exports.Variant = Variant;
//# sourceMappingURL=Variant.js.map

---

---

import {Entity, Column, PrimaryGeneratedColumn, OneToMany} from "typeorm";
import {Comic} from "./Comic";

@Entity()
export class Series {

    @PrimaryGeneratedColumn()
    public id: number;

    @Column("text", {
        length: 30
    })
    public copyright: string;

    @Column("text", {
        length: 100
    })
    public attributionText: string;

    @Column("text", {
        length: 150
    })
    public attributionHTML: string;

    @Column("text", {
        length: 50
    })
    public etag: string;

    @Column("text", {
        length: 200
    })
    public title: string;

    @Column("text")
    public description: string;

    @Column("number", {
        length: 4
    })
    public startYear: number;

    @Column("number", {
        length: 4
    })
    public endYear: number;

    @Column("text", {
        length: 20
    })
    public rating: string;

    @Column("text", {
        length: 20
    })
    public type: string;

    @Column("text")
    public thumbnail: string;

    @OneToMany(type => Comic, comic => comic.series)
    public comics: Array<Comic>;
}

---

---

import {Entity, TableInheritance, PrimaryGeneratedColumn, Column, ManyToOne, DiscriminatorColumn} from "typeorm";
import {Series} from "./Series";

@Entity()
@TableInheritance("class-table")
@DiscriminatorColumn({ name: "type", type: "string"})
export class BaseComic {

    @PrimaryGeneratedColumn()
    public id: number;

    @Column("text", {
        length: 30
    })
    public copyright: string;

    @Column("text", {
        length: 100
    })
    public attributionText: string;

    @Column("text", {
        length: 150
    })
    public attributionHTML: string;

    @Column("text", {
        length: 50
    })
    public etag: string;

    @Column("text", {
        length: 200
    })
    public title: string;

    @Column("int")
    public issue: number;

    @Column("text")
    public variantDescription: string;

    @Column("boolean")
    public variant: boolean;

    @Column("text")
    public description: string;

    @Column("int")
    public pageCount: number;

    @Column("date")
    public onSaleDate: Date;

    @Column("date")
    public unlimitedDate: Date;

    @Column("text")
    public thumbnail: string;

    @ManyToOne(type => Series, series => series.comics)
    public series: Series;
}

---

---

import {OneToMany, ClassEntityChild} from "typeorm";
import {Variant} from "./Variant";
import {BaseComic} from "./BaseComic";

@ClassEntityChild()
export class Comic extends BaseComic {

    @OneToMany(type => Variant, variant => variant.comic)
    public variants: Variant[];
}

---

---

import {ManyToOne, ClassEntityChild} from "typeorm";
import {Comic} from "./Comic";
import {BaseComic} from "./BaseComic";

@ClassEntityChild()
export class Variant extends BaseComic {

    @ManyToOne(type => Comic, comic => comic.variants)
    public comic: Comic;
}

推荐答案

我遇到了同样的问题。事实证明我是循环导入类，这显然是一个限制。 （请参阅以下GitHub问题：＃20361 ，＃4149 ，＃10712 ）

I was having the same issue. It turns out I was circularly importing classes, which is apparently a limitation. (See these GitHub issues: #20361, #4149, #10712)

请注意，循环引用似乎也限制在文件之间，而不仅仅是类型。

Note that it seems that the circular reference is also limited between files, not simply types.

请参阅此其他答案

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