Best Practice Advise for a Total Ruby Beginner

ruby-talk
1

Hey, I've just started running through the first edition of
"Programming Ruby" and I'm already enjoying this language. I'm not the
best programmer in the world (self-taught) so I'm coming here to ask
for advise. Here's the situation (simplified for example):

class Ticket
  def initialize( id )
    @id = id
    @messages = Array.new(0)
  end

  def addMessage( message )
    @messages << message #push message
    @messages = @messages.sort { |a,b| a.created <=> b.created } #sort by
create time
  end
end

class Message
  def initialize( created )
    @created = created
  end

  def created
    @created
  end
end

ticket = Ticket.new( 1 )
ticket.addMessage( Message.new( 2005 ) )
ticket.addMessage( Message.new( 1999 ) )

I found I had to make a method to access the "created" instance var in
the Message class in the sort block. I tried using a.@created and
b.@created but it threw a syntax error. So, my question: Is making a
method simply to access a var as in this case "good programming"?

Paul

2

Basically, yes. It's generally referred to as 'encapsulation' in object-oriented circles. One big advantage that's often cited is that if you change the internal representation of 'created' in Message (say, to seconds since 1970 or something), you only change the accessor method to maintain compatibility. If you directly accessed the variable, you'd have to change every piece of code that used Message to keep it compatible.

As I'm sure will be pointed out before I manage to send this off, Ruby provides some shortcuts for making these methods:

class Message
   attr :created
   def initialize(created)
     @created = created
   end
end

'attr' is a method which adds accessor methods to the class for its arguments. The arguments are symbols which correspond to variable names you want the accessors for.

matt.

···

On Dec 8, 2005, at 15:17, cros wrote:

I found I had to make a method to access the "created" instance var in
the Message class in the sort block. I tried using a.@created and
b.@created but it threw a syntax error. So, my question: Is making a
method simply to access a var as in this case "good programming"?

Paul

3

crosone wrote:

Hey, I've just started running through the first edition of
"Programming Ruby" and I'm already enjoying this language. I'm not the
best programmer in the world (self-taught) so I'm coming here to ask
for advise. Here's the situation (simplified for example):

class Ticket
  def initialize( id )
    @id = id
    @messages = Array.new(0)
  end

  def addMessage( message )
    @messages << message #push message
    @messages = @messages.sort { |a,b| a.created <=> b.created } #sort by
create time
  end
end

class Message
  def initialize( created )
    @created = created
  end

  def created
    @created
  end
end

ticket = Ticket.new( 1 )
ticket.addMessage( Message.new( 2005 ) )
ticket.addMessage( Message.new( 1999 ) )

I found I had to make a method to access the "created" instance var in
the Message class in the sort block. I tried using a.@created and
b.@created but it threw a syntax error. So, my question: Is making a
method simply to access a var as in this case "good programming"?

Paul

Do you mean code like this:

class Man
  attr_accessor :name # use 'attr_accessor' to access a parameter

  def initialize(name)
    @name = name
  end
end

foo = Man.new('Foo')
puts "Foo's name: #{foo.name}"

···

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