(Quick Reference)

Tag Library Usage

A tag library fulfills role of "view helper" in the Model View Controller (MVC) pattern and helps with GSP rendering. In Grails a tag library is a class with a name that ends in the convention "TagLib" and lives in the grails-app/taglib directory. Use the create-taglib command to create a tag library:

grails create-taglib format

or with your favourite IDE or text editor make a new file with the name FormatTagLib in grails-app/taglib as given below

import java.text.SimpleDateFormat

class FormatTagLib {
    def dateFormat = { attrs, body ->
        out << new SimpleDateFormat(attrs.format).format(attrs.value)

Each Closure property in a tag library that takes one or two arguments is considered a tag. The first argument (typically named attrs) will contain the attributes of the tag whilst the optional second argument (typically named body) is Closure that represents the inner HTML of the tag declaration from the GSP.