Question

I’ve created 2 domain classes called Asset and Tag. Asset can have many Tags

// Asset.groovy
class Asset {
    static hasMany = [tags: Tag]
}

// Tag.groovy
class Tag {
    static belongsTo = Asset
    String word
}

The tags are entered into a textfield in the View, each separated by commas.

When the Asset form is submitted, the AssetController will use Tag.findOrSaveWhere to either create a new Tag or Asset.addToTag

def tags_list = params?.tags?.split(",")
tags_list.each {
    def tag = Tag.findOrSaveWhere(word: it.trim())
    assetInstance.addToTags(tag)
}

All that works very well, but I’m trying to essentially remove Tags from an Asset if the user updates and deleted a Tag.

How can I remove Tags on update?

EDIT I’ve gotten a little further with this by taking an old approach of deleting all the tags then attempting to save the Asset instance.

assetInstance.tags.clear()
def tags_list = params?.tags?.split(",")
tags_list.each {
    def tag = Tag.findOrSaveWhere(word: it.trim())
    assetInstance.addToTags(tag)
}

However, this will throw an exception if the Tags are null. In other words, if I delete all tags, saving fails.

Answer 1

Solved my issue. Clearing the tags in the update action was the right move, but I had to be mindful of the empty tags string from the form.

My end result was the following block in my AssetController

assetInstance.tags.clear()
def tags_list = params?.tags?.split(",")
tags_list.each {
def tag = Tag.findOrSaveWhere(word: it.trim())
if (tag.id != null) // to prevent null id exceptions
    assetInstance.addToTags(tag)
}