I have a class called 'AStack'
Object subclass: #AStack
instanceVariableNames: 'elements'
...
It contains an OrderedCollection Object that holds it's 'element objects'
initialize
super initialize.
elements := OrderedCollection new
It's member classes push and pop, respectively:
push: anObject
self elements addFirst: anObject
pop
^self elements removeFirst
I am trying to write a print method that uses timesRepeat to print the contents of the stack as well as empty it simultaneously. It calls the child class print method for each 'element' (print ^self name) and outputs it on the screen using 'Transcript'.
print
self size timesRepeat: [ Transcript show: elements print. self pop ]
Workspace code:
| o1 o2 stk |
o1 := Object new.
o1 name: 'object1'.
o2 := Object new.
o2 name: 'object2'.
stk := AStack new.
stk push: o1.
stk push: o2.
stk print.
Upon running the above code I get an error within Pharo that says MessageNotUnderstood: AStack>>elements.
If you need more code on my part don't hesitate to ask.
As far as I can guess, error occurs in stk push: o1. as #push: uses self elements and probably you don't have #elements method in AStack.
Also for emptying your stack it will be more logical not to use self size timesRepeat: but [ self notEmpty ] whileTrue: [ … ] or other variations like [ self isEmpty ] whileFalse: [ … ]. It makes code more understandable.
And as we talk about understandability, usually people do not expect that #print method will destroy their collection :)