Ruby-on-rails 检查属性是否存在并设置的最佳方法是什么？
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What is the best way to check if an attribute exists and is set?
提问by Eric Norcross
I have a common view that lists two different models. The only difference is that when setting the link_toaction, one of the models has a linkattribute and the other doesn't. I want to check if the linkattribute exists, and if it does, check if it's set. I have the following which works, but I was wondering if there was a better way.
我有一个共同的观点，其中列出了两种不同的模型。唯一的区别是在设置link_to动作时，一个模型有一个link属性，另一个没有。我想检查该link属性是否存在，如果存在，请检查它是否已设置。我有以下工作，但我想知道是否有更好的方法。
%li
- if @element.has_attribute?("link") && @element.link
= link_to @element.title, @element.link
- else
= link_to @element.title, @element
回答by ck3g
回答by ahnbizcad
I believe you can just do @element.attribute?(e.g. @element.link?)
(I suppose we could call it "magic attributes".)
我相信你可以做@element.attribute?（例如@element.link?）（我想我们可以称之为“魔法属性”。）
This checks for
这检查
- the attribute existing on the model
- the value not being nil
- 模型上存在的属性
- 值不为零
Exactly what you want.
正是你想要的。
回答by OneChillDude
Try using the attributes hash. This hash will return a key => valuemapping of all of an activerecord object's attributes.
尝试使用属性哈希。这个散列将返回一个活动记录key => value对象的所有属性的映射。
if @element.attributes['link']
# Here we are
else
# default
end
