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We need to define the
init method for our Account
objects, so that our
new method defined above will work.
Here's the Smalltalk code:
!Account methodsFor: 'instance initialization'! init balance := 0 ! !
It looks quite a bit like the previous method definition,
except that the first one said
Account class methodsFor:..., and ours says
The difference is that the first one defined a method for
messages sent directly to
Account, but the second one is
for messages which are sent to Account objects once they are
The method named
init has only one line,
balance := 0.
This initializes the hidden variable
called an instance variable) to zero, which makes
sense for an account balance. Notice that the method
doesn't end with
^r or anything like it: this method
doesn't return a value to the message sender. When you do
not specify a return value, Smalltalk defaults the return
value to the object currently executing. For clarity of
programming, you might consider explicitly returning
in cases where you intend the return value to be used.(25)
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