CODEWITHSUNDEEP
oopinheritancetclincr-tcl
Vahagn
Vahagn

Reputation: 4830

How to check if one class is a base of another in [incr Tcl]?

Givetn two class names, className1 and className2, how can I check if className1 has className2 anywhere in its heritage?

Upvotes: 0

Views: 109

Answers (1)

Donal Fellows
Donal Fellows

Reputation: 137587

Alas, [incr Tcl] only supports introspection on objects and not on classes; you'll have to make an instance of className1, fetch its heritage with info heritage $theInstance, and check whether className2 is present in that list. Messy. (From 4.0 onwards you could use info class subclasses className2 className1 to check if className1 is a direct subclass of className2, but that doesn't work for indirect subclasses, i.e., with some subclasses in between.)

However, general principles of OO programming in Tcl would tend to indicate that you should use duck typing if you can: don't worry about whether the object is of the right class, worry about whether it can respond to the messages you want to send to it (i.e., the methods you want to invoke). Since any object can trap attempts to invoke unknown method calls, you can't really find out what it will actually do by introspection, and have to Just Try It. Or look for some documentation if you're lucky.

Upvotes: 4

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