Need help on groovy syntax

Question

I came across a groovy syntax that creates a link in gsp file like this:

class LoginTagLib {
def loginControl = {
out << """[${link(action:"login",controller:"user"){"Login"}}]"""
}}

I know that it will eventually turned into this in html:

<a href="/racetrack/user/login">Login</a>

---

However, there are 2 portion of the syntax that I don't understand:

1. I don't understand ${link(action:"login",controller:"user"){"Login"}} :

   • I get the $() , which is used for string interpolation.
   • I get the link(action:"login",controller:"user") too, just 2 arguments passed into link
   • but what is the {"Login"} doing behind?

2. I don't understand the """[ ]""" that is used to enclose the whole thing, I tried to take away a pair of " , but it wounldn't work anymore. So it proves to me it has it's significance.

Anybody help to shed some light?

Thanks

Answer 1

1. In groovy if the last argument of a function is a closure you can you change this syntax foo(arg1, arg2, ..., { ... }) to foo(arg1, arg2, ...) { ... } . this is what happens here, the last argument of link() is a closure that should evaluate to the textual representation of the link
2. ''' and ''' allow for multi-line string. """ """ are the same but also support variable substitution