CODEWITHSUNDEEP
grails
Farkas István
Farkas István

Reputation: 564

How to use Grails bindData when using collections in entity fields and properties

I have the following domain classes:

Airport:

class Airport {

  String airportName
  List<Flight> flights

  static hasMany = [flights: Flight]
  static mappedBy = [flights: "departureAirport"]

}

Flight:

class Flight {

  String flightName

  Integer numOfStaff

  Airport departureAirport

}

I have in a form the following input fields which is correctly prints the saved airport and it's flights:

<input name="airportName" value="${airportInstance.airportName}" />
<input name="id" value="${airportInstance.id}" />
<input name="version" value="${airportInstance.version}" />

<g:set var="counter" value="${0}" />
<g:each in="${airportInstance?.flights?}" var="f">

  <div>
    name : <input name="flights[${counter}].flightName" value="${f.flightName}" />

    id : <input name="flights[${counter}].id" value="${f.id}" />

    numOfStaff : <input name="flights[${counter}].numOfStaff" value="${f.numOfStaff}" />

    <g:set var="counter" value="${counter + 1}" />
  </div>

</g:each>

I post the form to the following controller action:

@Transactional
def update() {

  Airport airportInstance = Airport.get(params.id)

  // doesn't work as well
  // airportInstance.properties = params

  bindData(airportInstance, params)

  airportInstance.save flush:true

  request.withFormat {
    form multipartForm {
      flash.message = message(
                        code: 'default.updated.message', 
                          args: [
                            message(
                              code: 'Airport.label', 
                              default: 'Airport'
                            ), 
                            airportInstance.id
                          ]
                       )
      redirect airportInstance
    }
    '*'{ respond airportInstance, [status: OK] }
  }
}

When I modify airportName or some of the flights properties (e.g.: numOfStaff) and I click update (post it to the controller action), Grails does his work correctly and updates my changes.

But if I manually add a new instance in the view e.g.: if there were two flights flights[0] and flights[1] listed by g:each and I add flights[2] it doesn't create a new instance of Flight and doesn't save it. The same if I try to delete an existing flight from the view and post it to the controllers update action.

I'm using grails version 2.3.9

My questions are:

Am I doing something wrong? Is it a Grails bug or Grails developers implemented bindData method like this for some reason? What is the best way in Grails to implement issue like above (I mean giving the name attributes like foo[index].prop where foo is a collection in the entity).

Sorry for the junk html. Thank you guys, for the answers.

Upvotes: 2

Views: 1267

Answers (1)

Farkas Istv&#225;n
Farkas Istv&#225;n

Reputation: 564

I found the solution. If I declare a controller action like:

def update(Airport airport) {
  // ...
}

In this case before the controller action is executed Grails will automatically create an instance of the Airport class and populate its properties by binding the request parameters.

If there is an id request parameter then instead of invoking the domain class constructor to create a new instance a call will be made to the static get method on the domain class and the value of the id parameter will be passed as an argument. Whatever is returned from that call to get is what will be passed into the controller action. This means that if there is an id request parameter and no corresponding record is found in the database then the value of the command object will be null.

See Grails Reference Documentation: http://grails.org/doc/latest/guide/theWebLayer.html#commandObjects

Upvotes: 0

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