validate_holder_change


Description:

public virtual signal Error validate_holder_change (Holder holder, Value new_value)

Gets emitted when a Holder's in set is going to change its value.

One can connect to this signal to control which values holder can have (for example to implement some business rules)

Parameters:

holder

the Holder which is going to change

new_value

the proposed new value for holder

Returns:

NULL if holder is allowed to change its value to new_value, or a Error otherwise.