From: "Steve P." <stevepauly@...>
Date: 2010-07-31T09:06:21+09:00
Subject: Re: Beginner help needed: use a class def to create new instance

Jes��s Gabriel y Gal��n,

I was able to accomplish (at least crudely) moving code from the main 
body to the class. I felt this was worth doing because I want as much 
logic as possible in the class. (Is this a worthy thing??)

As you advised, I was able to create my new instance using a method that 
returned an object.

Could you please take a look at how I implemented these two methods? 
Account.setupaccount, Account.report

Is this how you would have structured it?
Any tips or comments greatly appreciated.
Steve.

#!/usr/bin/ruby
class Account
  attr_reader :nbr, :name, :coa
  def initialize(nbr,name,coa)
    @nbr=nbr
    @name=name
    setcoa(coa)
  end
  def setcoa(coa)
    if ["income", "expense", "asset", "liability",
     "capital"].include?(coa) then
      @coa=coa
    else
      puts "Error, defaulted to expense"
      @coa="expense"
    end
  end
  def Account.setupaccount
  #data entry routine inside class, not in main code body.
    print "enter acct nbr: ";nbr=gets.chomp
    print "enter name: ";name=gets.chomp
    print "enter presen: ";coa=gets.chomp
    return Account.new(nbr,name,coa)
  end
  def Account.report(acct)
  #reporting code inside class, not in main body.
    puts "===Account Number Listing==="
    puts "Account Nbr:         #{acct.nbr}"
    puts "Account Name:        #{acct.name}"
    puts "Account CofA:        #{acct.coa}"
  end
end
##Start of main code body ##
newacct=Account.setupaccount
Account.report(newacct)
##End of Main code body ##

When I clear my confusion about this, I will do something like
class Ledger < Account
  ##code to make an array of the Account objects and add more 
functionality
end



Jes��s Gabriel y Gal��n wrote:
> On Tue, Jul 27, 2010 at 6:36 AM, Steve P. <stevepauly@comcast.net> 
> wrote:
>> PS: I realize I can instantiate newchar=Character.new(da da da) from the
>> body of the code but that would require the prompting code be there
>> also. that would defeat my purpose. I hope I have given this enough
>> thought before posting! :-)
> 
> Two considerations:
> 
> - I tend to separate the domain objects from the code that interacts
> with the outside world to gather the data to populate that domain
> object (user typing, DB, etc). This way you gain flexibility, being
> able to add ways of loading or creating the object without modifying
> that class
> 
> - If, in any case, you want the interaction with the user in that
> class, I would use a class method that returns an instance. If you
> have other ways of creating that instance you can add new methods for
> each case. For example:
> 
> 
> #!/usr/bin/ruby -w
> 
> class Character
>   attr_reader :chname, :chnick, :chquote
>   def initialize(chname,chnick)
> ���   @chname=chname
> ��� ��� @chnick=chnick
> ��� ��� @chquote=String.new
>   end
> ��� def addquote(quote)
> ���   @chquote=quote if quote.length > 10
> ��� end
> ��� def self.from_prompted_input
> ��� ��� print "Char name: ��� ���";chname=gets.chomp
> ��� ��� print "Char Nick: ��� ���";chnick=gets.chomp
> ��� ��� print "Char Quote: ��� ��� ��� ��� ���";chquote=gets.chomp
>     Character.new chname, chnick,chquote
>   end
> end
> 
> puts Character.from_prompted_input.inspect
> 
> What you had in mind couldn't work, because your method was an
> instance method, so from the outside you still needed someone to call
> Character.new(x,y,z).promptedinput.
> 
> Having class methods to instantiate objects of the class in different
> ways is a pretty typical idiom, check for example the Date class in
> core:
> 
> http://ruby-doc.org/core/classes/Date.html
> 
> The methods civil, commercial, etc are class methods that return an
> instance, constructed in a different way.
> 
> Jesus.

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