WebdriverIO -在异步模式下按索引单击元素不起作用

Question

WebdriverIO不再支持同步模式，我目前正在过渡到异步模式。到目前为止，一切正常，但我注意到我的按索引点击/选择元素的方法停止了工作，例如，这在同步模式下可以很好地工作：

get expandButtons()  {return $$(faqLocators.expandButton)};

clickOnExpandButtonByIndex(index: number) {
    const expandButton = this.expandButtons[index]
    expandButton.waitForExist()
    expandButton.click()
}

但是相同的方法重写为异步模式会抛出一个错误，所以在我当前的实现中，上面的方法看起来是这样的：

async clickOnExpandButtonByIndex(index: number) {
    const expandButton = await this.expandButtons[index]
    await expandButton.waitForExist()
    await expandButton.click()
}

测试中的用法如下：

it('My test', async () => {
        await expect(faqPage.arrowDownIcon).toBeDisplayed();
        await faqPage.clickOnExpandButtonByIndex(0)
        await expect(faqPage.arrowUpIcon).toBeDisplayed();
    });

上面的代码抛出了以下错误：

 Cannot read property 'waitForExist' of undefined
 TypeError: Cannot read property 'waitForExist' of undefined
    at FAQPo.<anonymous> (/Users/badb/IdeaProjects/my-test-project/project/apps/retail-app-e2e/src/pages/FAQ/FAQ.po.ts:23:28)
     at step (/Users/badb/IdeaProjects/my-test-project/project/apps/retail-app-e2e/src/pages/FAQ/FAQ.po.ts:33:23)
    at Object.next (/Users/badb/IdeaProjects/my-test-project/project/apps/retail-app-e2e/src/pages/FAQ/FAQ.po.ts:14:53)
     at fulfilled (/Users/badb/IdeaProjects/my-test-project/project/apps/retail-app-e2e/src/pages/FAQ/FAQ.po.ts:5:58)
     at processTicksAndRejections (internal/process/task_queues.js:97:5)

 Cannot read property 'click' of undefined
 TypeError: Cannot read property 'click' of undefined
    at FAQPo.<anonymous> (/Users/badb/IdeaProjects/my-test-project/project/apps/retail-app-e2e/src/pages/FAQ/FAQ.po.ts:23:28)
     at step (/Users/badb/IdeaProjects/my-test-project/project/apps/retail-app-e2e/src/pages/FAQ/FAQ.po.ts:33:23)
    at Object.next (/Users/badb/IdeaProjects/my-test-project/project/apps/retail-app-e2e/src/pages/FAQ/FAQ.po.ts:14:53)
     at fulfilled (/Users/badb/IdeaProjects/my-test-project/project/apps/retail-app-e2e/src/pages/FAQ/FAQ.po.ts:5:58)
     at processTicksAndRejections (internal/process/task_queues.js:97:5)

我还有以下警告：

TS2532: Object is possibly 'undefined'.
TS2684: The 'this' context of type 'Element | undefined' is not assignable to method's 'this' of type 'Element'.   Type 'undefined' is not assignable to type 'Element'.

我在文档中读到，这是异步模式下的常见问题，但建议的解决方案在我的情况下不起作用。并且我无法单击按索引与多个元素交互。有人能解释一下如何在异步模式下实现上述方法吗？我参考了这篇文章https://webdriver.io/docs/sync-vs-async/

Answer 1

   const expandButtons = await this.expandButtons()

    const expandButton = await this.expandButtons[index]

Expand按钮是一个函数而不是数组，所以等待函数给元素数组，然后在其中调用index