From: Jim Weirich <jim@...>
Date: 2004-02-04T06:48:32+09:00
Subject: Re: Newbie question


Stephen Taylor said:
> We are two grey-haired programmers studying Ruby and have a question so
> basic we can't believe we 're unable to find an answer in "The Ruby Way"
> and
> "Ruby in 21 Days" or the online material.

Perhaps another grey-haired programmer can answer :-)

>
> Our class Money holds pennies as Fixnum values and its to_s method returns
> a
> string with the currency symbol prefixed. (Leave commas and decimal point
> for later.)
[... code elided ...]

> Question: can we create and set in one move? We imagine
>
>     n = Money.new(1234)
>
>
> But if we:
>
>     def Method.new(amt)
>         initialize
>         @value = amt
>     end

Remember that new is a class method, therefore references to @value inside
of new will reference the value attribute of the *class* object Money, not
an instance of Money.

Fortunately, the built-in version of new calls initialize after the object
is allocated.  Initialize is an instance method, so you can do what you
need in it.

For example

  class Money
    def initialize(value)
      @value = value
    end
    # ... rest of class here ...
  end


  n = Money.new(1234)   # Should now work.

-- 
-- Jim Weirich     jim@weirichhouse.org    http://onestepback.org
-----------------------------------------------------------------
"Beware of bugs in the above code; I have only proved it correct,
not tried it." -- Donald Knuth (in a memo to Peter van Emde Boas)