CODEWITHSUNDEEP
smalltalk
user2871898
user2871898

Reputation: 93

Printing from an OrderedCollection in Smalltalk

I am fairly new to Smalltalk and I'm stuck on how to print elements from a stack. I have two classes, one which creates the stack using OrderedCollection, which works, and a second class (Object subclass). For the second class I have two instance variables name and weight(with set and get methods). I need to make two more methods print and printSpecial. Print output the name and weight to the Transcript on the same line using the get method from name but cannot use the get method from weight. PrintSpecial is similar to print but the weight must be < 100. I have tried doing print and printScpecial but cannot figure it out. Below is what I have so far. Any help would be appreciated.

name: a
     name := a

name
     ^name

print
     [ Transcript
        show: weight;
        show: name;
        cr ]

printSpecial
    [ weight <= 100 ]
        whileTrue: [ Transcript
            show: weight;
            show: name;
            cr ]

Upvotes: 1

Views: 353

Answers (1)

Leandro Caniglia
Leandro Caniglia

Reputation: 14858

Both your print and printSpecial methods enclose their bodies in squared brackets. You should remove them. Try:

print
  Transcript
    show: weight;
    show: name;
    cr

printSpecial
  weight <= 100 ifTrue: [
    Transcript
      show: weight;
      show: name;
      cr]

Notice that in printSpecial I've replaced whileTrue: with ifTrue:. The reason is that you don't want to keep printing for ever if the weight happens to meet the condition.

Another thing I would suggest is to avoid repeating code. So, I would propose this:

printSpecial
  weight <= 100 ifTrue: [self print]

This way, if you later decide to improve print you won't have to copy the improvement to printSpecial.

Finally, you say you have a collection of these objects. Therefore you should have some way of enumerating them (e.g., via do:). Thus, if the actual request consisted in printing them all you should implement print and printSpecial in the elements' class and then implement the same messages in your Stack class.

Stack >> print
  collection do: [:elem | elem print]

Stack >> printSpecial
  collection do: [:elem | elem printSpecial]

where I'm assuming that the instance variable that holds your elements is named collection.

Even better. You could implement do: in your Stack class and then use self do: instead of collection do: as I did above. Something on the lines of

Stack >> do: aBlock
  collection do: aBlock

and then

Stack >> print
  self do: [:elem | elem print]

Stack >> printSpecial
  self do: [:elem | elem printSpecial]

Upvotes: 4

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