From: Robert Klemme <shortcutter@...>
Date: 2010-11-14T22:40:17+09:00
Subject: Re: more help with address book

On 14.11.2010 13:17, Aaron Haas wrote:
> I’m trying to create a simple address book in ruby.  It is made up from
> the following classes.  Address, Phone, Person, and AddressBook .  The
> Address, Phone, Person classes all work fine.  I’m having problems with
> several methods in my AddressBook class.
>
> Add(person) needs to check if that person already exists.  I tried using
> my query method but it only prints the name to the screen.  Can I make
> it also return an person object to use as a comparison?

You should remove the printing from the finding because this is a 
completely different aspect.  You basically have two options to improve 
this:

1. Change #query to return an Array of found items.

2. Change #query so that it yields every matching entry to a block 
passed to the method.

Advantage of both approaches is that you can reuse the query code in 
different situations.  I would go with version 2 but 1 might be easier 
to understand at first.  If you do 2 you could code like this

def print_query(name)
   query name do |person|
     puts person
   end
end

def query_first(name)
   query name do |person|
     return person
   end

   nil
end

def add(name, ...)
   raise "Person known already" if query_first(name)
   ...
end

> The prompt method should take a command (add, print, remove,  find,
> exit) then depending on which command ask the user for required
> information.   The command prompts should run continuously until “exit”
> is entered. The add command which is the most complicated of the five
> works fine for a single time.  I can’t figure out how to implement a
> while condition to keep it going without getting errors.

I would create a class per command.  This class can contain the prompt 
text as well as the evaluation logic.  You could then stuff instances of 
those classes in a Hash and just look them up via command.

But: I would remove the code from AddressBook.  Currently you are mixing 
model code (i.e. data management of address books) with user interface 
(output, prompting etc.).  That's usually considered bad because you mix 
logic with presentation.

> I’m also having problems with the remove method logic.  I built the
> remove method to take a variable name as a parameter, but the command
> prompt would require an first and last name instance fields from the
> person class.
>
> I'm getting close just a few tweaks here and there.
> This code is getting long one so I just attached the file.  If you think
> I should copy and paste let me know.

You could host this on github.  That way you also have version control 
and can look at the path of evolution later.

Kind regards

	robert

-- 
remember.guy do |as, often| as.you_can - without end
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