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Ruby gives us shortcuts to write common pieces of code. The process of accessing and writing attributes in a class can be done using `attr_writer` and `attr_accessor` to ease repeating code.
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In addition to the attr_reader method,
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Ruby gives us some other shortcut methods
for reading and writing attributes.
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Let's take a look at how those work now,
using workspaces.
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Now Ruby gives us some other methods like
attr_reader, that we can use in our code.
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And let's go ahead and see how this works
right now.
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If I open up IRB, I can load in this file
to work with,
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by typing the word load and the name of
the file.
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And what that will do, will be to load
this class into our IRB session.
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As if we had written it inside of IRB.
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So type load, and then a space, a quote,
and
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then the path to the file, which is this
directory,
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which is the dot, and a slash, the name of
the file, which is name.rb.
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Now you will notice that this gets
printed, but we don't quite have access
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to the instance variable name just yet, so
let's go ahead and create one.
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We will say name equals Name.new,
"Mr.", "Jason", "", "Seifer".
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Okay.
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Now we have this little name object that
we're working with.
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Since we put the attr_readers in here
that's going to
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allow us to read these different
attributes.
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So we could say name.title and it would
give us back the title.
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But we can't change that.
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For example, if I somehow became a doctor,
Ruby tells us there's an undefined
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method `title=' for this particular Name object.
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So, how would we do that?
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Let's go ahead and exit IRB here.
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And let's go back to this particular file.
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If I wanted to be able to reset the title
later,
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I would have to define a method to do it.
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[SOUND] And we do that by calling define,
and
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then the name of the method, which is
going
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to be the same as the instance variable
name.
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title, and then the equals sign.
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[SOUND] And then we pass in a new title.
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So now we type instance variable title
equals.
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This new title that's being called on the
method.
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So I'm gonna do a scroll down here.
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And just print out the title, put
name.title.
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And now we saw before when we were working
with this, we could not call name.title.
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Let's try it again.
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[SOUND] And we're just gonna print this
out twice,
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and let's be a little bit more thorough
here.
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[SOUND] And we can call that.
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[SOUND] Now the same code that didn't work
before.
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[SOUND].
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Go ahead and clear my screen.
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Now, if I run name.rb, we can see that the
title was changed.
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So, let's look at this.
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What we're doing is setting this title
instance variable to a new value which we
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send in to this method.
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Now this is a really common pattern,
again, in Ruby.
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So, Ruby gives us another way to work with
that and
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that is by defining a writer in addition
to a reader.
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And then Ruby will automatically take care
of this for us.
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[SOUND] So if I run this again, the same
thing
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is printed out, and Ruby is actually so
nice.
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That it wraps both of these patterns into
one different method call,
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which is called attr_accessor.
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[NOISE] So I could now take out that
[NOISE] and
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remove the title from the list of readers.
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[SOUND] And if I run this again the same
thing should print out.
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Now you might be wondering why you would
ever use attr_reader and
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attr_writer instead of just using
attr_accessor.
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The difference is thinking about it in
terms of readability of your code.
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You may only ever be reading certain
attributes, like a first name,
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middle name and last name, and only
writing certain attributes.
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Be as explicit as possible.
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If you know you're only going to be
reading certain attributes,
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only set those as a reader.
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And the same thing with writing
attributes.
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