GNU Smalltalk - Inheritance and Multiple Parameter Methods/Constructors

Question

Say I\'m trying to translate the below Java classes to GNU Smalltalk:

public abstract class Account {

    protected String number;
    protected Customer cu         


        

Answer 1

1. You shouldn't bother with some kind of "making class abstract" :). But the closest solution to your question is

   abstractMethod [
       self subclassResponsibility
   ]
   

   Now when someone sends a message to your class he'll get an error that this method should be implemented, and you must override it in subclasses.

2. Yes. All instance vars can be accessed by a subclass.

3. Ok, so the keyword messages like withdraw: amount can actually have multiple parameters like: withdraw: amount becauseOf: reason. So first of all you make an initialiser:

   initWithBalance: aBalance customer: aCustomer number: aNumber [ 
       self init.
       balance := aBalance.
       customer := aCustomer.
       number := aNumber
   ]
   

   You can keep interest := 0. in main init. Then, to make your life better, you make a parameterised new and call parameterised init from there.

   SavingsAccount class [
       newWithBalance: aBalance customer: aCustomer number: aNumber [
          ^ self new initWithBalance: aBalance customer: aCustomer number: aNumber
       ]
   ]