From: dblack@...
Date: 2007-08-04T03:21:43+09:00
Subject: Re: Beginner's tutorial and poor attempt at classes

Hi --

On Sat, 4 Aug 2007, Gabriel Dragffy wrote:

>
> On 2 Aug 2007, at 15:18, dblack@rubypal.com wrote:
>
>> Hi --
>> 
>> On Thu, 2 Aug 2007, Gabriel Dragffy wrote:
>> 
>>> Hi all
>>> 
>>> I just started with Ruby (yesterday actually). Have been reading the 
>>> amazing Poignant Guide, and also a couple of other very basic tutorials. 
>>> From one of these I wrote an example class, now my knowledge of Ruby has 
>>> expanded a little I tried to rewrite the class to be even better.  I 
>>> thought that the method "setme" would allow the @numberShowing to be 
>>> changed to any number between 1 and 6... but obviously not...?
>>> 
>>> 
>>> #/usr/bin/env ruby
>>> 
>>> class Die
>>> def initialize
>>>  roll
>>> end
>>> 
>>> def roll
>>>  @numberShowing = 1 + rand(6)
>>> end
>>> def showing
>>>  @numberShowing
>>> end
>>> 
>>> def setme value
>>>     if value === 1..6
>>>    @numberShowing = value
>>>  else
>>>    puts "A dice has only six sides!"
>>>  end
>>> end
>>> 
>>> end
>> 
>> You've got the === backwards; you want:
>>
>>  if (1..6) === value
>> 
>> or
>>
>>  if (1..6).include?(value)
>> 
>> Here's a little rewrite, using a reader attribute to streamline the
>> retrieval of the die's number:
>> 
>> class Die
>>  attr_reader :number
>>
>>  def initialize
>>    roll
>>  end
>>
>>  def roll
>>    self.number = rand(6) + 1
>>  end
>
>
> Have been rereading your example. Just wanted to ask why in the code just 
> above did you use  "self.number"  which you changed from @number?
>
>
>>
>>  def number=(value)
>>    if (1..6).include?(value)
>>      @number = value
>>    else
>>      puts "A die has only six sides!"
>>    end
>>  end
>> end
>
> and then here "@number" is used.. finding this a little confusing. Thanks 
> again, for all your help.

The number= method does some data checking, and if all is well it sets
@number.  I don't want to set @number directly, because the checking
won't happen.  I guess rand(6) + 1 is pretty safe, but still, since my
setter method does more than just set @number, it's "polite" to go
through that method instead of just setting @number.


David

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