Issue 144  3rd December 2018

Map with Default

I found the withDefault operator while migrating a Grails plugin to Grails 4. I was not aware of it.

def m = [:].withDefault { key ->
    new Date().toString()
}
String firstAccess = m['foo']
String secondAccess = m['foo']
assert firstAccess != null
assert firstAccess == secondAccess

Create a List with Default Values

Yes, there is a withDefaultfor List to.

Since Groovy 1.8.7 we can create a list and use the withDefault() method to define a default value for elements that are not yet in the list. We use a closure as argument of the method, which returns the default value. We can even access the index of the element in the closure as an argument.