TypeError：无法设置未定义的属性“ xxx”

Question

我是打字稿新手，我编写了这段代码来测试一个方法，

describe('book', () => {

    let hostelClient: HostelClient;


    it('should book', async () => {

        hostelClient.getRequestByIdAsync = jest.fn().mockReturnValue({});

        // Assert
        let exceptionThrown = false;
        expect(exceptionThrown).toBe(false);
     });

});

但是我有这个错误：

 TypeError: Cannot set property 'getRequestByIdAsync' of undefined

和

@Service()
export class HostelClient  {

    constructor() {
        throw new Error('not allowed);
    }
..
}

Answer 1

请尝试以下操作：

describe('book', () => {

let hostelClient: HostelClient = new HostelClient();


it('should book', async () => {

    hostelClient.getRequestByIdAsync = jest.fn().mockReturnValue({});

    // Assert
    let exceptionThrown = false;
    expect(exceptionThrown).toBe(false);
 });
});

在您的示例中，您定义，但没有将变量实例化为新的hostelClient。