A $once constraint is evaluated once at construct time. It will be
evaluated when the attribute is given its default value. If the
constraint depends on other attributes in the same class, there will
be a problem, because there is no particular order of initialization
specified. In the case where you have mutually dependent attributes
that you want to initialize once, you would be better off using an
onconstruct method.
On 2007-01-31, at 13:18 EST, Antun Karlovac wrote:
Maybe I should rephrase that last question: "is there a situation
where you would have to worry about init order with $once{}
constraints?
-Antun
Antun Karlovac wrote:
Yes usually I'd use $once{}, but I'm sure that there have been
times when I've had to use a $always{} (i.e. ${}) constraint
because of init order issues.
Do $once{} constraints do the same checking-for-init that normal
constraints do?
-Antun
