Ruby on Rails

Hi all,

In Rails console (just doing a general exercise in ruby design
patterns), I create two classes:

ruby-1.9.2-p136 :023 > class A
ruby-1.9.2-p136 :024?> attr_accessor :name, :balance
ruby-1.9.2-p136 :025?> def initialize(name, balance)
ruby-1.9.2-p136 :026?> @name = name
ruby-1.9.2-p136 :027?> @balance = balance
ruby-1.9.2-p136 :028?> end
ruby-1.9.2-p136 :029?> def <=>(other)
ruby-1.9.2-p136 :030?> balance <=> other.balance
ruby-1.9.2-p136 :031?> end
ruby-1.9.2-p136 :032?> end
=> nil
ruby-1.9.2-p136 :033 > class Portfolio
ruby-1.9.2-p136 :034?> include Enumerable
ruby-1.9.2-p136 :035?> def initialize
ruby-1.9.2-p136 :036?> @accounts = []
ruby-1.9.2-p136 :037?> end
ruby-1.9.2-p136 :038?> def each(&block)
ruby-1.9.2-p136 :039?> @accounts.each(&block)
ruby-1.9.2-p136 :040?> end
ruby-1.9.2-p136 :041?> def add_account(account)
ruby-1.9.2-p136 :042?> @accounts << account
ruby-1.9.2-p136 :043?> end
ruby-1.9.2-p136 :044?> end
=> nil

client code:
ruby-1.9.2-p136 :045 > portfolio = Portfolio.new
=> #<Portfolio:0x00000105d47118 @accounts=[]>
ruby-1.9.2-p136 :091 > a = A.new('n',1000)
=> #<A:0x00000105fdc478 @name="n", @balance=1000>
ruby-1.9.2-p136 :092 > portfolio.add_account(a)
=> [#<A:0x00000105fdc478 @name="n", @balance=1000>]
ruby-1.9.2-p136 :093 > b = A.new('b',2000)
=> #<A:0x00000105fd0ba0 @name="b", @balance=2000>
ruby-1.9.2-p136 :094 > portfolio.add_account(b)
=> [#<A:0x00000105fdc478 @name="n", @balance=1000>, #<A:
0x00000105fd0ba0 @name="b", @balance=2000>]
ruby-1.9.2-p136 :095 > portfolio.each {|n, b| n <=> b }
NoMethodError: undefined method `balance' for nil:NilClass

It appears that the each iterator does not support passing in two
arguments? because I expect n to be object 0x00000105fdc478 and I
expect b to be object 0x00000105fd0ba0. Then I expect once the each
iterator of portfolio is called and executed, we in turn call each on
the array of accounts, passing in our block. When that call occurs, we
invoke the defined <=> instance method of A class, passing in the two
objects stored in @accounts. This in turn will call the <=> method of
enumerable and perform comparison operation. However, what I just
described above does not occur.

thanks for response

--
You received this message because you are subscribed to the Google Groups "Ruby on Rails: Talk" group.
To post to this group, send email to rubyonrails-talk@googlegroups.com.
To unsubscribe from this group, send email to rubyonrails-talk+unsubscribe@googlegroups.com.
For more options, visit this group at http://groups.google.com/group/rubyonrails-talk?hl=en.