使用安全的殿堂操作员，然后比较结果
我真的不知道该如何为自己想做的事情留下明确的标题。
我正在与ROR合作，在一个控制器中，我有此声明：
recipe.cover_image.attach(data: params[:recipe][:cover_image]) if params[:recipe][:cover_image] && params[:recipe][:cover_image].length > 255
因此，我试图使用安全的导航操作员进行更紧凑和易于阅读的内容，类似的事情：
recipe.cover_image.attach(data: params[:recipe][:cover_image]) if params[:recipe][:cover_image]&.length > 255
但是它不起作用。我明白了：
undefined method `\u003e' for nil:NilClass
问题是当零是什么时候，它会做类似的事情：nil＆gt; 255？
有办法这样做吗？安全导航操作员之后的另一个动作？
I really don't know how to put a clear title for what I am trying to do.
I am working with RoR and in a controller I have this statement:
recipe.cover_image.attach(data: params[:recipe][:cover_image]) if params[:recipe][:cover_image] && params[:recipe][:cover_image].length > 255
So I was trying to use the safe navigation operator for doing it a bit more compact and easy to read, something like this:
recipe.cover_image.attach(data: params[:recipe][:cover_image]) if params[:recipe][:cover_image]&.length > 255
But It doesn't work. I got this:
undefined method `\u003e' for nil:NilClass
The problem is that when is nil, it does something like: nil > 255 ?
Is there a way to do this? Another action after the safe navigation operator?
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简而言之，您可以将
.to_i添加到.length的末尾，以确保您比较类型。例如，您遇到该错误的原因是
nilclass没有一种称为＆gt;的方法。但是，nilclass确实具有.to_i方法，该方法总是返回0。由于＆gt;是Integer和0的方法是Integer，因此比较将 just just join 。In short, you can add
.to_ito the end of.lengthto ensure you're comparing like types. E.g.The reason you're getting that error is that
NilClassdoes not have a method called>. However,NilClassdoes have a.to_imethod, which always returns0. Since>is a method onIntegerand0is anInteger, the comparison will just work.