Is there a way to get local state variables to be unique for different objects? See my example bank account: class Acc @@balance = 100 def withdraw( amount ) if @@balance >= amount @@balance = @@balance - amount else "Insufficient Funds" end end @@balance end irb(main):012:0> check1 = Acc.new => #<Acc:0xb7dc2f14> irb(main):013:0> check1.withdraw 50 => 50 irb(main):014:0> check1.withdraw 40 => 10 irb(main):015:0> check1.withdraw 25 => "Insufficient Funds" This is great - but if I create a new object 'check2' it doesn't start with a new balance of 100. What am I doing wrong here? irb(main):016:0> check2 = Acc.new => #<Acc:0xb7db08c8> irb(main):017:0> check2.withdraw 40 => "Insufficient Funds" I wanted this to return 60
on 2009-03-18 06:42
on 2009-03-18 06:58
Jason L. wrote: > end > end > @@balance > end @@balance is a _class_ variable, shared by all instances of the class (and potentially subclasses), you probably want an instance variable: class Acc def initialize bal @balance = bal end def withdraw( amount ) if @balance >= amount @balance = @balance - amount else "Insufficient Funds" end end end acc = Acc.new 100 puts acc.withdraw(12) puts acc.withdraw(120)
on 2009-03-18 07:14
ah, thank you. Interesting how in Lisp (Scheme) you have to do: (begin (set! balance (- balance amount)) balance) to decrement the balance and change it's state - using the set!