Typescript class.default 不是构造函数

Typescript class.default is not a constructor

提问by Nandan Phadke

Creating an Angular2 app, I am facing the following problem, when calling the constructor of another class inside the constructor of first class.

创建一个 Angular2 应用程序，当在第一类的构造函数中调用另一个类的构造函数时，我面临以下问题。

First Class code

一级代码

import SecondClass from './second-class'

export class FirstClass {
    someVar:string;
    secondClass:SecondClass;

    constructor(firstClass?: FirstClass) {
        someVar='test';
        secondClass= new SecondClass;
    }
}

Second Class code:

二级代码：

export class SecondClass {
    someOtherVar:string;

    constructor(secondClass?:SecondClass) {
        someOtherVar='test';
    }
}

Would give me the error: ORIGINAL EXCEPTION: TypeError: second_class_1.default is not a constructor

会给我错误：ORIGINAL EXCEPTION: TypeError: second_class_1.default is not a constructor

Content of ./second-class

./second-class 的内容

System.register([], function(exports_1, context_1) {
    "use strict";
    var __moduleName = context_1 && context_1.id;
    var SecondClass;
    return {
        setters:[],
        execute: function() {
            SecondClass = (function () {
                function SecondClass(secondClass) {
                    this.someOtherVar='test';
                }
                return SecondClass;
            }());
            exports_1("SecondClass", SecondClass);
        }
    }
});
//# sourceMappingURL=second-class.js.map

This is the compiled output from Typescript compiler

这是 Typescript 编译器的编译输出

回答by dfsq

Error message implies that you used named export (export class SecondClass {}) in ./second-class(not default). So it means that your import should looks something like

错误消息暗示您export class SecondClass {}在./second-class（非默认）中使用了命名导出 ( )。所以这意味着你的导入应该看起来像

import {SecondClass} from './second-class'

回答by tibbus

There are some errors in the code :

代码中有一些错误：

• missing {}from import

• missing ()from calling the constructor

• missing thisfrom accessing Class members

• {}导入时丢失

• 缺少()调用构造函数

• 缺少this访问类成员

First Class code

一级代码

import {SecondClass} from './second-class'

export class FirstClass {
    someVar:string;
    secondClass:SecondClass;

    constructor(firstClass?: FirstClass) {
        this.someVar='test';
        this.secondClass= new SecondClass();
    }
}

Second Class code:

二级代码：

export class SecondClass {
    someOtherVar:string;

    constructor(secondClass?:SecondClass) {
        this.someOtherVar='test';
    }
}

回答by Timo

this is too late, but I just got the same error right now. Solution is export SecondClassas default so Second Class code will be:

这太晚了，但我现在遇到了同样的错误。解决方案是SecondClass默认导出，因此二等代码将是：

export default class SecondClass {
    someOtherVar:string;

    constructor(secondClass?:SecondClass) {
        this.someOtherVar='test';
    }
}

and import in other class with import SecondClass from './second-class'

并在其他类中导入 import SecondClass from './second-class'