Re: tutorial: "doesNotUnderstand" instance variable

Cédrick Béler wrote:
> The error message says that #existSides: doesn't exist. So either you 
> create it (the accessor) or you directly affect the instance variable.
>
> BlankCell>>existSide: aDictionary
>        existSide := aDictionary
>
> or you replace in you initialize method "self exitSides: Dictionary" 
> new by:
> existSide := Dictionary new

Where are you getting "existSides"?  Everything I see in the stack 
screen shot and in my email says "exitSides"?



I'm going to assume that was a mistake, and you're suggesting the same 
thing Karl mentioned.

If I do this, it "doesNotUnderstand" the following line.  But I see the 
var is set, so I remove self from all the following lines.  The accessor 
complains similarly, and I remove self from it also.

It works, but I'm confused and concerned now.  Why does the tutorial ( 
http://squeak.preeminent.org/tut2007/html/021.html ) recommend the other 
form, and why does that form work for activeSegments (my other instance 
variable, which is also a Dictionary) but not exitSides:

initializeActiveSegments
   self activeSegments: Dictionary new.
   self activeSegments at: #north put: false.
   self activeSegments at: #east put: false.
   self activeSegments at: #south put: false.
   self activeSegments at: #west put: false.

In my mind, I now have two instance variables of Dictionarys that I have 
to initialize and reference in different ways.

I just realized activeSegments has an accessor / mutator pair.  So, is 
this an omission of the tutorial, forgetting to mention the those 
methods?  Am I correct in concluding methods calls are always prefixed 
by the class instance variable name (in this case "self) while instance 
variables of self are referenced directly?