withFormat

Purpose

Used to execute different responses based on the incoming request Accept header, format parameter or URI extension. See content negotiation for more information.

Examples

import grails.converters.*
class BookController {
	def books
	def list = {
		this.books = Book.list()
		withFormat {
			html bookList:books
			js { render "alert('hello')" } 
			xml { render books as XML }
		}
	}
}

Description

The withFormat method takes a block within the scope of which you can execute different methods whose names match the content type you want to respond to. For example:

withFormat {
	html bookList:books
	js { render "alert('hello')" } 
	xml { render books as XML }
}

Here we invoke three methods called html, js and xml that use mime type names configured in grails-app/conf/Config.groovy (See content negotiation for more information). The call to html accepts a model (a map) which is passed on to the view. Grails will first search for a view called grails-app/views/book/list.html.gsp and if that is not found fallback to grails-app/views/book/list.gsp.

If you require the model the be lazily executed you can pass a closure or block instead of a map:

withFormat {
	html { [bookList:Book.list()] }
    …
}

The block will only get executed if the html format is matched.