如何在Grails 3的编辑视图中修改ID列的值？

Question

How do you allow the values of the ID columns to be modified at runtime in Grails 3? In my case, I have a table with a composite primary key consisting of three columns. I manually specified them to appear in the edit view and my update() method code looks like this:

@Transactional
def update(AliasFrequencyDict aliasFrequencyDict) {

    aliasFrequencyDict = AliasFrequencyDict.get( new AliasFrequencyDict(params) )

    if (aliasFrequencyDict == null) {
        notFound()
        return
    }

    aliasFrequencyDict.properties = params

    try {
        aliasFrequencyDict.save(insert: false, flush: true)
    } catch (ValidationException e) {
        respond aliasFrequencyDict.errors, view:'edit'
        return
    }

    request.withFormat {
        form multipartForm {
            flash.message = message(code: 'default.updated.message', args: [message(code: 'aliasFrequencyDict.label', default: 'AliasFrequencyDict'), aliasFrequencyDict.getPK()])
            redirect(action: 'show', params: params)
        }
        '*'{ respond aliasFrequencyDict, [status: OK] }
    }
}

...and when I go into edit view and edit the property not being part of the key, it saves correctly but as soon as I change one of the other ones, I get a message reading that Grails could not found an AliasFreuqencyDict instance of ID null. I guess the problem is that, once you change one of such columns, the ID changes too and Grails somehow doesn't know how to switch from the primary key that the object used to have to the new ones.

How should I modify the controller to allow for editing the part-of-key columns too, then?

Answer 1

The (most obvious) problem here is the way you're looking up the one you want to update. If you share your domain model for AliasFrequencyDict I can be more specific, but say you have a composite key of First and Last and an instance where [first:"John", last:"Doe"] .

Now you update that to set first=Jane and press update... you are creating a new AliasFrequencyDict for "Jane Doe" and using that in the lookup of .get() , of course that's not going to return an instance of AliasFrequencyDict . If you're changing the value of a PK field, you'll need to pass in the old values to look up the object, and then set the new values accordingly.