The oo::configurable class is a part of TclOO in Tcl 8.7. It is a metaclass, i.e., it modifies how you create classes, adding the capability to define properties on the class. It also modifies the class to add a configure method (via a mixin). The configure method is aware of the properties defined across the inheritance hierarchy for the class.
In particular, this means that if one does:
oo::configurable create Point {
property x y
constructor args {
my configure -x 0 -y 0 {*}$args
}
variable x y
method print {} {
puts "x=$x, y=$y"
}
}You can then do:
set pt [Point new -x 27]
$pt print; # x=27, y=0
$pt configure -y 42
$pt print; # x=27, y=42
puts "distance from origin: [expr {
hypot([$pt configure -x], [$pt configure -y])
}]"; # distance from origin: 49.92995093127971
puts [$pt configure]
# -x 27 -y 42That can then be extended with more properties by a subclass:
oo::configurable create Point3D {
superclass Point
property z
constructor args {
next -z 0 {*}$args
}
}
set pt2 [Point3D new -x 2 -y 3 -z 4]
puts [$pt2 configure]
# -x 2 -y 3 -z 4