“可见?"和“存在?"有什么区别? [英] What's the difference between `visible?` and `present?`?
问题描述
从 Watir API 中，我得出了两个断言(当然可能不正确):
From the Watir API, I've derived two assertions (which of course might not be correct):
- 如果我只想验证元素是否在 HTML 中，我可以使用
exists?.我不在乎它是否可见. - 如果我希望能够在页面上看到它，我可以使用
visible?.
- I can use
exists?if I simply want to verify that the element is in the HTML. I don't care if it's visible or not. - I can use
visible?if I want to be able to see it on the page.
那么，我什么时候使用present??
So, when do I use present??
在我看来，我可以这样回答我自己的问题:
It seems to me that I could answer my own question by saying:
- 如果我想在页面上看到它，我可以使用
present?，但我不希望它出现在 HTML 中.
- I can use
present?if I want to be able to see it on the page, but I don't want it to be in the HTML.
所以，如果我用记号笔在屏幕上写一些东西，它会出现吗??
So, if I write something on the screen using a marker pen, would that be present??
(对不起，如果我看起来不敬.)
(Sorry if I seem to be irreverent.)
那么 - 标题中提出问题的另一种方式 - 我什么时候应该使用 visible? 什么时候应该使用 present??
So - another way to ask the question in the title - when should I use visible? and when should I use present??
推荐答案
visible? 和 present? 的区别在于该元素不存在于 HTML 中.
The difference between visible? and present? is when the element does not exist in the HTML.
当元素不在 HTML 中时(即 exists? 为 false):
When the element is not in the HTML (ie exists? is false):
visible?会抛出异常.present?将返回 false.
visible?will throw an exception.present?will return false.
我倾向于使用 present? 因为我只关心用户是否可以看到该元素.我不在乎它是否因为通过样式隐藏而无法看到，例如 display:none;，或者不在 DOM 中，例如它被删除了.如果应用程序实际上将不在 DOM 中的元素视为不同于在 DOM 中但不可见的含义，我只会使用 visible?.
I tend to stick with present? since I only care if a user can see the element. I do not care if it cannot be seen due to it being hidden via style, eg display:none;, or not being in the DOM, eg it got deleted. I would only use visible? if the application actually treats the element not being in the DOM as a different meaning than being in the DOM but not visible.
例如，给定页面:
<html>
<body>
<div id="1" style="display:block;">This text is displayed</div>
<div id="2" style="display:none;">This text is not displayed</div>
</body>
</html>
查找不在页面上的 div 时可以看出区别:
You can see the difference when looking for a div that is not on the page:
browser.div(:id => '3').visible?
#=> Watir::Exception::UnknownObjectException
browser.div(:id => '3').present?
#=> false
对于页面上的元素，两种方法是一样的:
For elements on the page, the two methods will be the same:
browser.div(:id => '1').visible?
#=> true
browser.div(:id => '1').present?
#=> true
browser.div(:id => '2').visible?
#=> false
browser.div(:id => '2').present?
#=> false
这两种方法的比较以及 exists? 可以在 Watirways 书.
A comparison of these two methods along with exists? can be found in the Watirways book.
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