3.3 Traits

Slate objects, from the root objects down, all respond to the message traits, which is conceptually shared behavior but is not as binding as a class is. It returns an object which is, by convention, the location to place shared behavior. Most Slate method definitions are defined upon some object's Traits object. This is significant because cloning an object with a traits delegation slot will result in a new object with the same object delegated-to, so all methods defined on that traits object apply to the new clone.

Traits objects also have their own traits object, which is Traits traits. This has the important methods defined on it for deriving new prototypes with new traits objects:

myObject derive

will return a new clone of the object with a traits object which is cloned from the original's traits object, and a delegation slot set between the traits objects.

myObject deriveWith: mixinsArray

will perform the same operation, adding more delegation links to the traits of the array's objects, in the given order, which achieves a structured, shared behavior of multiple delegation. Note that the delegation link addition order makes the right-most delegation target override the former ones in that order. One interesting property of this method is that the elements of mixinsArray do not have to be Derivable.

As with any method in Slate, these may be overridden to provide additional automation and safety in line with their semantics.