- Welcome 1:30
- Object-Oriented Programming 2:29
- Object-Oriented Programming 5 questions
- Types 3:14
- Instantiation 6:28
- Types and Objects 5 questions
- Instantiation 2 objectives
- Fields 6:18
- Fields 1 objective
- Object Initialization 5:14
- Initialization 3 objectives
- Practice Writing Classes 3:40
- Wrap-up 4 questions
Preview
Video Player
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Practice Writing Classes
3:40Now you try. Write a class on your own, then we'll walk through it together.
Let's take another look at
a graphical representation of a map.
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We need to be able to specify where on
the map a tower or an invader is located.
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We can think of our map as being
divided up into a two-dimensional grid.
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Each grid square is a location where
an object can be placed on the map.
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This allows us to use Cartesian
coordinates to identify grid squares.
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Cartesian coordinates are used to identify
a point on a two-dimensional grid.
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Traditionally variables named X and
Y are used to specify a point.
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X is the distance from
the left-most grid square.
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Y is the distance from
the bottom-most grid square.
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A tower located at the bottom left corner
of the map would be located at x=0, y=0.
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And this tower is placed at point x=3 and
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y=1 or point 3, 1 for short.
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Where is this tower located at?
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That's right.
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It's at point 5,4.
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So a point on the map has both an X and
a Y coordinate.
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Let's model a point using a class.
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We'll need to create a new
file called Point.cs.
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We'll define this class inside
the Treehousedefense namespace.
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So our Point class is going to look
very similar to our map class.
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It will have two fields,
one called X and one called Y.
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Just like our Map class
needs both a width and
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a height, the Point class will
need both an X and a Y coordinate.
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You know everything you need to
know to write the Point class.
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I suggest you pause the video here,
and go ahead and
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do that on your own for practice.
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Then when you come back,
we'll work through it together.
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All right, how do you think you did?
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Let's take a look.
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We'll make a class and call it Point.
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Then we'll have two public fields in
our class, one for X, and one for Y.
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We'll make them both integers, and
they'll both be public because we'll need
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to be able to read them
from other classes.
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Points don't move, so
we need to make both X and Y readonly.
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We'll need to add a constructor
to initialize X and Y.
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It will need to be public and
take an x and y parameter.
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We'll use these parameters to set
the value of the X and Y fields.
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There we have it.
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As I said, the point class looks
almost identical to the Map class.
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Only the names are different.
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What it means to be a point and
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what it means to be a map are still
two very different things though.
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Remember to compile your code to
make sure that you're not getting
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any compiler errors.
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If you do get compiler errors, check
to make sure that your code looks like
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the code written in these videos and
that all of your files are saved.
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Way to go.
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You're writing classes and
you're making objects.
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Objects are a fun way to think about
designing software, don't you think?
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As we learn more about the capabilities
of C# to do object-oriented programming,
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it's going to get even
more interesting and fun.
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We are off to a great start,
but this is just the beginning.
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We've learned about classes and fields.
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Next we'll learn about methods and
their role in objects.
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