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[MUSIC]

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Hi, I'm Jason, and welcome to
Build an Address Book with Ruby.

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We're going to be building a command
line program that will let someone

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put in the names and
information of all of their contacts.

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Then, we'll add in the ability to go
through, and search these contacts.

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We're going to create our own classes for

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each different part of
the address book program.

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This will encompass the address book
itself, contacts, and their information.

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What we're doing is
abstracting away the logic

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of these different parts of
the program into their own classes.

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This is a good example of
object oriented programming.

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The process of figuring out what
logic goes to what class or

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object is called domain modeling.

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But that's not really super
important to remember.

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Now, we have to start somewhere so
we'll go ahead and start with the user or

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contact class.

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Go ahead and launch a workspace, and

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we'll begin to create the class
which will hold our contact.

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Okay, so the first class that
we're going to create for

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our address book is the contact class.

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The contact is going to encompass the idea
of one of the people in your address book.

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So let's go ahead,
I've launched a new Ruby workspace here.

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And go ahead and hit File, and New File,
and we'll name this contact.rb.

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So here we are, and
now we can go ahead and create our class.

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Now let's think about what
the contact is going to have.

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The contact for our purposes will have
a first name, middle name and last name.

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Now we're going to want to refer
to those a little bit later,

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so for right now, let's go ahead and
create attribute writers for those.

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And since we have the writers, let's go
ahead and create methods to read them.

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So, the first_name method is going
to return the first_name variable.

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The middle_name method is going to
refer to the middle_name variable,

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and the last_name method is going
to refer to the last_name variable.

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Now, at the bottom of this file, let's
go ahead and just create a new contact,

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make sure everything is working okay,
and we'll say json.first_name is Jason.

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I don't have a middle name.

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And my last name is Seifer.

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And let's go ahead and
just print out that contact.

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Now I'm going to click down into
the bottom console here, and

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type ruby contact.rb.

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Okay, we have a contact.

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And let me just go ahead and put
the first_name, space, and a last_name.

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And just make sure that
this is working correctly.

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Okay, that looks good.

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Now when we think about our address book,

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we may want to refer to
a contact in different ways.

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Maybe we want to print out their
full name, like we did right here.

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So let's go ahead and
create a full_name method,

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that will print out
the contact's full name.

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And instead of actually printing it out,
let's just go ahead and

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return a string of the full name.

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Now if we were just returning this,

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we could do first_name,
middle_name, and last_name.

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Now watch what happens
if we print this out.

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We'll just print Jason.full_name.

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Now notice I don't have a middle initial.

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So when we print this out,
there's a little space right here.

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So let's go ahead and fix that.

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And instead of doing this, let's go ahead
and assemble this full name in parts.

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So we'll say the full_name
is equal to the first_name.

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Now right here full_name is just a local
variable inside the full_name method.

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It's okay to name variables the same thing
as methods when you are inside a method.

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You're not gonna have any conflict.

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So we've got full_name and
then we can say,

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if the middle_name is nil.

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If the middle name is not nil, what we'll
do is add a space to this full name.

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And then add the middle_name method which
returns the variable to that full_name.

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And now we can just add
the last_name onto it.

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And then we just return this variable.

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And we do an implicit return as
the last line of the method.

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Then when we run this,
we can see that works correctly.

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And let's go ahead and
try one with a middle_name.

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All right.

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And we run that again.

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And this works correctly.

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And that is a pretty good
start to our contact class.