javascript - Typescript class.default 不是构造函数

Question

创建 Angular2 应用程序时，在第一类的构造函数中调用另一个类的构造函数时，我遇到了以下问题。

一级代码

import SecondClass from './second-class'

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

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

二等舱代码:

export class SecondClass {
    someOtherVar:string;

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

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

./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

这是 Typescript 编译器的编译输出

Answer 1

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

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