templates - Play Framework 2.0 template condition - when

Question

I can't find any documentation of what "when" means in scala template. I've seen it on multiple places like scala samples - forms application. What is the meaning of when, what it's suppose to do when it's true and respectively when it's false? Are there any restriction for this construct? Is there a place where I can see the description of this and others scala template constructs?

Sample code snippet:

<li class="@("active".when(nav == "signup"))">

Thank you

Answer 1

可以看到 when 2.0.4 / 2.1.0的定义。

它是 RichString 的成员，它按名称接受一个布尔谓词。String 被隐式转换为 RichString。

这意味着您只能在字符串上使用 when，并且您必须将其传递给布尔类型的参数。

谓词为真时返回字符串，假时返回空字符串。