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Wrapping Up
6:28In this video, we'll review the solution to the third and final challenge.
How did it go?
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Let's take a look at my solution.
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In the Album.cs file,
I added a constructor
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to the Album class, public Album.
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Remember, a constructor
should have the same name
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as the class that it's contained within.
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Then you follow the name with a set of
parentheses and a set of curly braces.
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Then I added a parameter for
each of the Album's required fields.
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I only have two fields, Title and
Artist, and both of them are required.
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So I added title and artist parameters,
both of type string.
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Notice that I used a lowercase letter for
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my parameter names,
just like I would for variable names.
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Then I set the fields to
the parameter values.
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So Title with a capital t =
title with a lowercase t.
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Then Artist with a capital
A = Artist with lowercase a.
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Because C# is case sensitive, the compiler
can understand that this Title
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with a capital T refers
to the title field,
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while this title with a lowercase
t refers to the title parameter.
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Then I moved on to adding constructors
to the Book and Movie classes.
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First, I'll save my file,
then open Book.cs.
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Public, to make sure that
we can call the constructor
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outside the class, Book,
parentheses, curly braces.
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Then my parameters,
string title and string author.
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Then initialize the field values
using the parameter values.
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Title, title, then author,
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oops, with a capital A, = author.
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Cmd+S to save the file,
then open Movie.cs.
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Public, again, Movie(), curly braces.
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Add my parameters.
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So string title and string director.
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Then initialize the field values
with the parameter values.
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Title with a capital T =
title with a lowercase t.
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And Director, with a capital D,
= director with a lowercase d.
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Command+S to save the file,
or Ctrl+S on Windows.
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In the Program.cs file Main method,
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I needed to pass the necessary arguments
to my immediate type class constructors
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If I don't do this,
I'll get errors when I compile my program.
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Since I already had the string literal
values here that I wanted to use,
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I just copied and pasted each into
the appropriate constructor call.
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Then I can remove these lines of code
that were setting the field values.
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And then the movie.
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First the title, Then the director.
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Going to remove some white space just
to tighten this up a little bit.
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There, that looks better.
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Lastly, I compiled and ran my program.
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And here's the expected output,
which is what we got last time.
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But this time, our code is using
our media type class constructors
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instead of setting
the field values directly.
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Adding constructors to our media type
classes helps to make our code clearer and
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more concise.
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It's worth noting though that an object's
field value can still be changed after
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its been instantiated.
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Let's take a look at that.
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After instantiating
this Album instance and
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writing its field values to the console,
let's make a change.
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Specifically, let's make
a change to the Title field.
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I'll change the field value to
Let It Be instead of Yellow Submarine.
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Then let's write the album field
values to the console again.
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Save and compile, and run our application.
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Here we can see the album
title Yellow Submarine,
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which is what we passed
to the class constructor.
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And here we can see the album title,
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Let It Be, which is what we
changed the field value to.
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As you saw in the C# objects course,
we can update our class field definitions
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in order to prevent a field value from
being changed after it's been initialized.
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To do that,
we just need to add the readonly keyword.
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This may or may not be something
that makes sense to do.
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Think about which object attributes
might change over time and
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those that shouldn't change.
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For my Album media type,
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these field values don't have
a reason to change over time.
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If they did change, it would more more
sense to create a new Album instance than
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to update an existing Album.
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The same logic applies to my
other media type classes,
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so I'll make the same change
to those classes too.
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And Movie.
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Great job completing
this practice session.
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Be sure to check out the next
session in this series
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after you've completed the second
stage in the C# objects course.
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Thanks for practicing with me,
and we'll see you next time.
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