Griffon Tip: Silly SwingBuilder Tricks

Here's two quick tips for working with radio buttons in SwingBuilder.  Radio buttons are created using SwingBuilder's radioButton() method.  To ensure only one is selected at a time, you must also associate them with a button group.   Ideally SwingBuilder would allow you to nest your radioButton()s inside a buttonGroup(), e.g.

buttonGroup() {
    // doesn't work
    radioButton(text: 'Option 1')
    radioButton(text: 'Option 2')
}

Unfortunately this doesn't work as buttonGroup() does not support nesting.  Marc Hedlund stumbled across this same issue and offers up one solution.  I like his solution but it means creating a separate variable to hold the button group.  I've found a bit nicer way to do it using Groovy's with keyword:

buttonGroup().with {
    add radioButton(text: 'Option 1')
    add radioButton(text: 'Option 2')
}

The advantage of this approach is that it conveys our intention better and we don't have to instance extra variables.

EDIT: the 'with' also passes in the created object so you could take it a step further and replace the add as well:

buttonGroup().with { group ->
    radioButton(text: 'Option 1', buttonGroup: group)
    radioButton(text: 'Option 2', buttonGroup: group)
}

As a bonus, here's how you can use mutual binding to keep a boolean in your model in sync with the radio buttons.  Let's say your model looks something like so:

class DemoModel {
    ...
    @Bindable boolean option1 = true
    ...
}

Using mutual binding, you can keep the model synced up without any explicit management code:

buttonGroup().with {
    add radioButton(text: 'Option 1', selected: bind(source: model, sourceProperty: 'option1', mutual:true))
    add radioButton(text: 'Option 2', selected: bind { !model.option1 })
}

Obviously this will only work for cases where you have an either-or choice.