Skip to main content


The @detached decorator is used to mark a method that is invoked when a certain critical property of the ConditionBlock is detached (set to undefined) and the ConditionBlock is therefore about to be removed from the form definition (since its state becomes invalid). The decorator can be useful to interfere in this process and gives an opportunity to convert the condition block to a new valid state.

Decorator type

Method ℹ️

Applies to

Decorator signature

@detached(property: string)

Decorator parameters

propertystringNoSpecifies the property of the ConditionBlock to observe.

Decorated method signature

(): (() => boolean) | void

Decorated method return value

The return value of the decorated method specifies what happens with the ConditionBlock. If you return nothing, the block will be removed. But if you return a function, that function is invoked just before the ConditionBlock will be removed. If that function, in turn, returns true the block is no longer deleted. This is useful for condition blocks that can be converted to a new valid state and therefore may remain in the form.