On Fri, 01 Dec 2017 19:07:01 -0700 Larry Leszczynski <lar...@emailplus.org> wrote:
> Hi all - > > I have triggers set up on two attributes that check if their values > are consistent with each other. I'm worried that since triggers get > called during construction when the values are passed in, it will try > to do the check before both of those attributes have been set. I > kinda only want to do the check inside BUILD (at which point I know > everything has been set), or later on when one or the other of those > attributes changes. > > I know how to call my checking code both from inside BUILD and as a > trigger, what I don't know is how to make the trigger *not* fire > during the initial construction... which makes me wonder whether > there is a different/better way to do it without using triggers. > > For purposes of discussion assume I have an attribute "color" which > can be red/blue/green, and another attribute "size" which can be > small/medium/large, and that any combination of color and size is ok > except I want to croak if you try to use color "red" with size > "small". > > > Thanks! > Larry Howdy Larry L., Take a look at some old blog posts from nothingmuch: http://blog.woobling.org/2009/08/moose-triggers.html In a nutshell: consider doing the check only during BUILD, avoid mutable state, make a separate class to contain those attributes and rebuild it as needed, or make the attributes private and provide a more sophisticated method for altering them that does the check explicitly. HTH, nperez
