- Introduction to Serialization 2:02
- Intro to Serialization 3 questions
- Soccer Player Data 3:40
- Using Json.NET 3:29
- Deserializing with Json.NET 4:44
- Deserializing with Json.NET 4 objectives
- Cleaning up the Player Class 5:00
- Cleaning up the Player Class 3 objectives
- Top Ten Scorers 8:54
- Serializing to a File 4:27
- Serializing to a File 4 objectives
Preview
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Top Ten Scorers
8:54We'll determine the top ten scoring players using List.Sort and the IComparer interface.
We're ready to do our analysis of
the top ten players in the MLS.
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Let's make a method that will calculate
the top ten players by points per game,
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and return them in a list.
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Public static Get TopTenPlayers, whoops.
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And we'll give it a list of
all the players, players.
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We'll need to first sort the players
by the points per game property in
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descending order.
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The list type has a method on
it called sort, players.sort.
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Let's check out the docs for
it by hitting F1, here it is.
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When you use the sort method with strings,
it'll just sort them alphanumerical.
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But since our list has objects,
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we'll need to tell the sort method
how to sort the elements in the list.
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We can do that by using a comparer.
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Let's click on that version here.
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Sorts the elements in the entire
list using the specified comparer.
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Let's click on IComparer here.
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Defines a method that a type
implements to compare two objects.
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IComparer is an interface which
you might not have seen before.
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An interface contains signatures
of properties and methods for
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which a class can implement.
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It's like a blueprint.
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It tells us how we
should create our class.
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So in order for us to implement this
IComparer interface to use in our method,
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we'd need to make sure that
it has this method compare.
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Let's check that one out,
this method has two parameters of type T,
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which in our case would be player and
returns in int.
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Back in our code,
we can create a new class for
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our comparer at Class and we'll call it
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PlayerComparer We'll
change this to public,
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and we'll need to inherit
from the IComparer interface,
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IComparer of Player.
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Notice that the IComparer of
Player has a red squiggly line.
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Visual Studio is telling
us that our PlayerComparer
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does not implement interface
member IComparer Player,
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because we haven't added the compare
method that the interface defines.
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So inside the class, we'll need
to create a method named Compare
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that matches the signature of
the method in the interface.
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We can use quick actions like we did
before with adding the namespace, but
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this time hitting Ctrl+period.
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Here it says Implement interface, and
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it even shows us a preview of the method,
we'll choose that.
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This method will return an integer based
on the comparison between player X and
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player Y.
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Now we need to add the logic inside
the method that determines which one is
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greater than the other based on
the points per game value of each player.
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Let's go back to the docs for
that compare method, so
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that we can figure out
what we need to return.
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A signed integer that indicates
the relative values of X and
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Y, as shown in the following table.
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If X is less than Y, we'd return a number
less than zero like negative one.
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If they're equal then we'd return zero.
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And then if x is greater than y,
then return something greater than zero,
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like one.
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Now back in our Compare method,
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let's start with the first
scenario where x is less than y.
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If X.pointspergame is less than
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y.pointspergame then
will return negative one.
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Then we'll do an else if x.pointspergame
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is equal to y.pointspergame
then return a zero
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and one more else if x.pointspergame
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is greater than y.pointspergame,
then return one.
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And down here at the end,
we'll just return a 0 to make it happy.
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This seems like it should work just fine,
but I think there's a cleaner,
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more concise way to
determine this comparison.
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All types at implement
Icomparable like string and
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and end in double have
a method called compared to.
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Our points per game property is a double,
ao should have that method on it.
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Let's check it out
xpointspergame.compareto,
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Compares this instance to
a specified object and
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returns an integer that indicates whether
the value of this instance is less than
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equal to or greater than
the value of the specified object.
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What a mouthful, but
that is exactly what we need.
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Now we can take out all of our logic and
replace it with one line of code.
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If
x,pointspergamecompareto(y.pointspergame),
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and not an if we just need to return
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the result of the compare to method.
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Let's get back to our top ten players and
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we can call the list.sort
with our new comparer.
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Sort(new PlayerComparer()); And
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return players; but we only want
to return the first ten players.
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So let's add a loop and a counter so
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we can break out of the loop
once we've printed out ten.
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We'll need a new list
to store our players.
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var top ten players = new list of player.
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We're missing a return type too.
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Then in here, we' ll make ourselves
a counter, int counter =0.
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And then, a foreach ( var player in
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players) then we'll add a player
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to topTenPlayers.Add, a player.
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Then we'll increment our counter,
and once the counter gets to ten,
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counter = 10 then we'll
just break out of the loop.
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Then we'll need to return topTenPlayers.
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All right now up in our main method, we
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can use this foreach loop to print all the
players from our get topTenPlayers method.
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var top ten players = get
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toptenplayers and pass it all the players
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then we'll need to copy/paste here for
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each player in top ten players, and
we'll right a little more to the console.
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Let's right out Name, FirstName and
then we'll print out the points.
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We'll say PPG, for points per game.
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Then the player.PointsPerGame.
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All right let's run it, F5.
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Uh-oh.
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Looks like we've got a bug.
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We sorted points per game ascending and
not descending, so
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we got the players with the least
amount of points per game.
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Why don't you take a moment after this
video to see if you can fix this bug?
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And in the next video I'll
show you how I would do it.
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