You are mixing up class and instance side :)

#canUnderstand: is send to instances #includesSelector: is sent to classes

(Integer canUnderstand: #readFrom) ==> (Integer class includesSelector: #readFrom:)

The instance side equivalent of canUnderstand: is #respondsTo:.. #includesSelector: is class side too but does not look in superclasses. So you have: Integer respondsTo: #readFrom: --> true Integer class canUnderstand: #readFrom: --> true Integer class includesSelector: #readFrom: --> true

On 2013-04-20, at 20:01, Milan Mimica <milan.mimica@gmail.com> wrote:

...

How come this evaluates to false? Integer canUnderstand: #readFrom: --> false Integer includesSelector: #readFrom: --> false

However, it does implement the method. Integer readFrom: '1' readStream. --> 1

-- Milan Mimica http://sparklet.sf.net