How to do proper data binding in Grails - grails

Question

I'm trying to do standard flow with adding entity to DB. Flow should look like this:
User opens link example.co/connection/putForm
edit all fields
submit (POST) to example.co/connection/put
if no errors then he is redirected to ../conncetion/index otherwise he should see previous form with all fields filled (step 2) and error message
For now my code looks like this:
def putForm() {
[
providers: Provider.findAll(),
cities : City.findAll()
]
}
#Transactional
def put() {
// not important part of parsing fields from params
def provider = Provider.get(params.provider)
def startTime = parseStartTime(params)
def path = parsePath(params)
def departurePlace = params.departurePlace
def connection = new Connection(provider: provider, startTime: startTime, departurePlace: departurePlace, path: path)
if (connection.save()) {
redirect controller: 'connection', action: 'index', params: [addedConnection: connection.id] // this part is OK
} else {
render view: 'putForm', params: params, model: [connection: connection] // this sucks... look below
}
}
The problem is that I need to render view putForm but from link .../connection/put. This cause problem that after this render all text fields are empty (step 4 above). Also I have ugly link.
Does Grails has any pattern for this common situation?
PS I cannot use scaffolding.

Answer 1

You're not that far off.. try this:
def putForm() {
[
providers: Provider.findAll(),
cities : City.findAll(),
connection: new Connection() // everything defaulted to empty or whatever you want the default to be
]
}
#Transactional
def put( Connection connection ) {
// NOTE: by putting the connection as the parameter to this action,
// all params.X that match a property X in the connection will auto-
// populate, even the Provider, assuming the value of params.provider.id
// is the id of a provider or blank (in which case
// connection.provider will be null.
// Skip this now
//def provider = Provider.get(params.provider)
//def startTime = parseStartTime(params)
//def path = parsePath(params)
//def departurePlace = params.departurePlace
//def connection = new Connection(provider: provider,
// startTime: startTime, departurePlace: departurePlace, path: path)
if (connection.save()) {
redirect controller: 'connection', action: 'index',
params: [addedConnection: connection.id] // this part is OK
} else {
render view: 'putForm', model: [
providers: Provider.findAll(),
cities : City.findAll(),
connection: connection]
}
}
The thing you need now is to make sure your putForm.gsp actually uses the values you sent down. You should put in things like:
<g:input name="path" type="text"
value="${fieldValue( bean:connection, field:'path' )}" />
and
<g:select name="provider.id" from="${providers}" // note the .id in places here
value="${connection.provider?.id ?: ''}"
noSelection="['':'None']"/>
Note that these will populate with whatever is in the connection sent down each time the page is rendered. So the first time it'll just have the default values, and if it has to rerender due to errors, it'll have the connection values that failed validation.
Hope this helps.