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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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00:00:39,080 --> 00:00:42,821
Y is the distance from
the bottom-most grid square.

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00:00:42,821 --> 00:00:48,561
A tower located at the bottom left corner
of the map would be located at x=0, y=0.

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00:00:48,561 --> 00:00:53,356
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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00:00:59,741 --> 00:01:00,741
That's right.

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00:01:00,741 --> 00:01:03,301
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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00:01:07,480 --> 00:01:10,150
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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00:01:24,764 --> 00:01:28,904
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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00:01:33,480 --> 00:01:35,800
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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00:01:40,710 --> 00:01:44,680
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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00:02:04,801 --> 00:02:09,762
Then we'll have two public fields in
our class, one for X, and one for Y.

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00:02:09,762 --> 00:02:13,848
We'll make them both integers, and
they'll both be public because we'll need

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00:02:13,848 --> 00:02:16,560
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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00:02:25,132 --> 00:02:28,850
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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00:02:45,243 --> 00:02:46,503
There we have it.

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00:02:46,503 --> 00:02:52,620
As I said, the point class looks
almost identical to the Map class.

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Only the names are different.

41
00:02:55,210 --> 00:02:56,960
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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00:03:01,520 --> 00:03:04,350
Remember to compile your code to
make sure that you're not getting

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00:03:04,350 --> 00:03:05,930
any compiler errors.

45
00:03:05,930 --> 00:03:09,380
If you do get compiler errors, check
to make sure that your code looks like

46
00:03:09,380 --> 00:03:12,680
the code written in these videos and
that all of your files are saved.

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00:03:14,200 --> 00:03:15,270
Way to go.

48
00:03:15,270 --> 00:03:18,460
You're writing classes and
you're making objects.

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00:03:18,460 --> 00:03:22,422
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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00:03:30,282 --> 00:03:32,880
We are off to a great start,
but this is just the beginning.

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00:03:34,170 --> 00:03:36,420
We've learned about classes and fields.

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00:03:36,420 --> 00:03:39,530
Next we'll learn about methods and
their role in objects.