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Welcome back, I hope you enjoyed
the section 15 challenge.

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I'm going to give you my solution
here, and we'll walk through it.

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As always, there's a lot of
different ways to do this.

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So if your solution is different
from mine, it's probably just fine.

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So I'm in the section 15 workspace
in the ChallengeSolution project.

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So I didn't change the account or
the savings account classes at all.

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So why don't we start with
the checking account class.

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This is one of the new
classes that we added.

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So let me open up the checking
account header file, and let's

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go through this real quickly.

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Now in this case, the checking account
doesn't add any new attributes, right.

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So a checking account is an account.

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I chose to derive this from account
because the checking account has

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the name and it's got a balance.

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The only difference here is that
when we withdraw, we're doing

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a $1.50 flat fee, check fee.

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Okay, so other than that it's
really, really very similar.

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We've got our const expressions
here, which are just our

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compile time constants.

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Here we've got our constructor
that expects a name.

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And if it's not supplied, we'll
use our default here, a balance.

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And that's it, right.

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The per check fee is
not a per object thing.

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This is a class thing.

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So this is why it's a
static cost expression.

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If it was on a per account basis
and obviously you'd want that to

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be an attribute and you'd want
to pass it into a constructor.

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So we've got that.

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We've got our withdraw method
because we need to override

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the behavior for withdraw to
deal with the per check fee.

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The deposit method is fine.

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We don't need to change that
at all because the way we do

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deposits is the same way that
an account does a deposit.

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Hopefully, one of the things that you
notice when you derive these classes

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from existing classes is the amount
of code you have to write is really

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minimal in many cases, right, because
all you're doing is specializing.

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The other thing we did here
was we created that overloaded

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insertion operator that works with
a checking account that just makes

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it really easy to display those.

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Okay, so that's it.

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Let’s take a look at
the implementation.

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And as you can see, there's
really very little code here.

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First of all, let's
look at the constructor.

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So there's my checking
account constructor.

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It expects the name and the balance.

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And I need to initialize the
account part of me, right

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because I'm derived from account.

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So here I'm invoking my base
classes constructor and it's the

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one that takes care of name and
balance I'm just passing it over.

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And when this comes back,
we're initialized, right.

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At that point, that's all.

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That's all we need for
a constructor here.

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Now what about the withdraw method.

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Well, here we're definitely
overriding the withdraw method.

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So here's the withdraw method for the
new class my checking account class.

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It still expects an
amount to withdraw.

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And all we're doing is we're saying
okay whatever that amount is I'm

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just adding the per check fee to it,
which is a 1.50 dollar in this case.

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So whatever, I want to withdraw
I'm just adding the 1.50 dollar.

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And then I'm letting the
account class do the withdrawal,

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just like we've done before.

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And again, I'm returning
what it returns.

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So if it fails, I'll return false.

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If it succeeds, I'll return true.

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And then the last thing we'll
do is our output operator

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here, our insertion operator.

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This time it expects
a checking account.

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And actually we could have used
used a regular account here,

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right because we're not really
adding anything in this class.

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So even if it got sliced,
it's okay because we're

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not adding anything at all.

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So that's it.

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That's a pretty simple implementation
of that checking account.

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Now let's take a look
at the trust account.

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So here we have our trust account.

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And you can see that the trust
account is derived publicly

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from a savings account.

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And that's because a trust
account has a name, a

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balance and an interest rate.

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So a lot of the savings account
behavior will be perfect for that.

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I'm overloading the insertion operator
here for a trust account as usual.

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And now this code looks
a little lengthier.

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And the reason for that is
all these constants here.

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They're handy, right.

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Here's our default balance,
here's a default interest rate.

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You probably could make that
2 or 3% or something just

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to get some more interesting
results, but I'll leave it at 0.

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There's the bonus amount for a
deposit that's over 5000 dollars.

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There's the threshold that's 5000.

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The maximum withdrawals is 3,
and the most we can withdraw

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is 20% of the accounts value.

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So all that information is right
in here in these constants.

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And the only thing that the
trust account really adds is

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besides the business logic, of
course, is this attribute right

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here the number of withdrawals.

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So it will set that to 0 when we
create a trust account object.

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And then every time we do a
withdrawal, that's successful,

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we'll bump it up by 1.

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And then when we do a withdrawal
and it's greater than 3, we'll just

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fail right there, pretty simple.

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Okay, so here's my constructor.

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It expects as usual, a name, a
balance and an interest rate.

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You can see that right there.

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And it's got these defaults right
up here that it defaults to.

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Here's my deposit, which I
obviously need to override

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because I've get a 50 dollar
whenever I deposit 5000 or more.

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And here's my withdrawal which
again I need to override because our

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business logic says I'm only allowed
maximum of 3 withdrawals per year,

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and each one is up to a maximum of
20% of the accounts value or balance.

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Okay, so that's it.

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Let's take a look at the
implementation file now.

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And here's the implementation
file for the trust account.

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You can see our
constructor is up here.

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Again, we're receiving the name,
the balance and the interest rate.

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And all of those guys are really
in my savings account part, right.

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So I'm invoking my base
class constructor right here,

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and I'm passing in name,
balance and interest rate.

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Let it take care of
initializing itself.

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When I come back, I do need
to take care of my attribute,

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which is number of withdrawals.

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So this is my responsibility, and
I'm setting that to 0 right here.

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Okay, so now let's take
a look at the deposit.

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So here's the trust
account deposit method.

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Again, it expects an amount.

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And all I'm looking for is that bonus
threshold which is 5000 dollars.

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So if the amount deposited is greater
than or equal to that bonus threshold,

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which in again in this case is
5000, then we're just incrementing

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the amount to deposit by the bonus
amount which is the 50 dollars.

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Simple as that, I invoke my base
classes deposit method because the

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savings account knows how to deal with
the interest rate and the deposit.

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And I'm returning right
here what it returns to me.

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And then the last thing we'll
do is our withdraw method.

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Again, the withdraw method's
important because it's got

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some business logic here.

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So I want to check -- and
again, here's the amount

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that I want to withdraw.

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So if the number of withdrawals
is greater than or equal to the

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max withdrawals, which was that
constant, which was 3 or the amount

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to withdraw is greater than the
balance times the threshold, right,

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so that's the 20% right here.

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If either one of those guys
is true, we don't do the

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withdrawal, we return false.

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Otherwise, we increment the number
of withdrawals, and we call our

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savings account withdraw method
and pass in the account -- and

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pass in the amount to withdraw.

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So that's it.

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You can see that we really
aren't writing a lot of new code.

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We're specializing, we're tweaking,
we're refining if you will our

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behavior based on our business logic.

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And then the last thing is
this overloaded insertion

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operator for trust account.

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In this case, I'm also displaying
the number of withdrawals just

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so that we have that information.

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Okay, so that's the trust account.

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So we've got our two new
accounts in the hierarchy now.

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So the next thing I want to show you
is that account util file and the

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functions that I modified in there.

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So let's look at the changes I
made to the account util files.

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And you can see that right here
I've added the function prototypes

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for the checking account class
and the trust account class.

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You can see that all this code is
really, really, really similar.

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And you're going to love what's
going to happen in the next section.

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We're going to be able to get
rid of all of this and just

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create one version that works
for all of the accounts once

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we use polymorphic functions.

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But for now, let's just do
it this way so that we really

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understand what's going on.

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Again, remember, we're doing
static binding right now.

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So the compiler is binding
the method calls to the actual

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types of the objects that
it sees in at compile time.

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So there are the function
prototypes for these guys.

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It's very similar to
what we did before.

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And the implementation
file right here, same idea.

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I'll just scroll down
just a little bit.

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And you can see here are the helper
functions for the checking account

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class right here on line 64.

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And if we scroll down a little
bit further, we've got the helper

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functions for the trust account class.

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And as I said, they're all exactly the
same except what's inside that vector.

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Okay, so now let's look at the main.

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Finally, here's the main and
the beginning is exactly the

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same as it was before, right.

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You remember we had the accounts tests
right here, so we put in some account objects

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into a vector of accounts
and then we call display,

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deposit and withdraw for those accounts.

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We did that both for a regular
account and a savings account here.

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And now we're just going
to do the same thing again

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for a checking account.

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So you can see here I'm
creating a vector of checking

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account objects, right.

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That's my template argument
right here, checking account,

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and it's check accounts.

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And I'm creating an empty checking
account, one for Kirk, one for

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Spock and, one for Bones, let's say.

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I don't want to give
Spock two accounts.

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And that's it.

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Then we're going to call display
for check accounts, deposit a 1000

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into each one of those accounts and
withdraw from those accounts 2000.

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And then finally, we're going
to do the trust account.

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And the trust account, same idea.

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I'm going to have a vector
of trust account objects.

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And I'm going to create
four of them again.

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I'm going to construct this
one with no initialization,

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just like I've done before.

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And then we'll create Athos, Porthos
and Aramis, the three musketeers.

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And we'll create some
accounts for them.

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We'll display them, deposit
into them and withdraw from

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them, just like we did before.

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And then the last thing I'm
doing is I'm simply calling

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withdrawal five times.

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So I'm looping five times,
and I'm calling withdraw

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on those trust accounts.

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So I expect those to fail,
right because I'm only allowed

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to withdraw 3 times maximum.

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And I can only withdraw
20% of the balance.

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So I should see a
lot of failures here.

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So let's run this.

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And there's going to be a
lot of output to go through.

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And you can see we have a clean
compile, no errors, no warnings.

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And I'll scroll up here because
there's a lot of output to go through.

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And this is what we
had earlier, right.

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When we created just the regular
accounts here, we created four

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of them: Larry, Moe Curly and
an unnamed account right up top.

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We're going to display them.

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That's what you're seeing right here.

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Then we're going to
deposit a 1000 into them.

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And that's this piece you see right
here, depositing two accounts.

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And then we're withdrawing
2000 from them that's the

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piece you see right here.

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The first two fail because
there's insufficient funds.

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So that's pretty straightforward.

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That's exactly what the default
code was in the challenge.

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So is this.

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Here's my savings accounts.

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Let me just scroll up to so
we can see that right here.

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So we're creating those four
savings accounts for superman,

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batman and wonderwoman.

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There they are.

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When we display them, we're depositing
a 1000 dollars into them here,

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and then we're withdrawing 2000.

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So of course, the first two will
fail because there's insufficient

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00:11:36,440 --> 00:11:37,520
funds, just like before.

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00:11:38,150 --> 00:11:39,300
Now here's the checking.

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The checking is a little different
now because our withdraw methods

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add a $1.50 service fee
or a per check fee, right.

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00:11:46,070 --> 00:11:50,959
So here we've got a checking account
for an unnamed checking account.

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We've got Kirk, Spock and Bones.

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And you can see them right here.

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00:11:56,589 --> 00:11:59,069
Right here is our display, right.

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There's our unnamed checking
account with 0 balance.

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There's Kirk, 0 balance, Spock
and Bones 2000 5000, respectively.

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I'm depositing a $1000
into each account.

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And then I'm going to withdraw 2000
from each account, exactly the

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same we've - as we've done before.

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00:12:16,529 --> 00:12:17,929
So the first two are going to fail.

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00:12:18,199 --> 00:12:20,720
And you can see that the numbers
now are a little different right

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because we are subtracting the
$1.50 per check fee here.

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And these two don't because
the withdrawal failed.

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But in this case, we did withdraw so
we're assessing the $1.50 fee.

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So you can see that indeed
the specialized withdraw

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method is being called.

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00:12:37,140 --> 00:12:39,090
Now finally, we've got
the trust accounts.

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So there's our code for the
trust account, and I'll scroll

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00:12:41,780 --> 00:12:42,920
that up right about there.

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So here I'm creating Athos Porthos
and Aramis and an unnamed trust

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account, right here at the beginning.

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And we're creating some different
balances as well as interest rates.

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And then we're just displaying
the accounts and that's what

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00:12:57,140 --> 00:12:58,080
you're seeing here, right.

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00:12:58,080 --> 00:13:01,530
The unnamed trust account with
0 balance 0% interest rate.

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It has no withdrawals yet.

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00:13:03,450 --> 00:13:04,959
Here's Athos Porthos and Aramis.

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00:13:04,959 --> 00:13:07,120
And you can see their
information right here.

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00:13:07,440 --> 00:13:10,080
Notice how all of them have
0 withdrawals because we

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00:13:10,080 --> 00:13:11,960
set that in our constructor.

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00:13:12,389 --> 00:13:14,479
Now we're going to call
deposit on each one of them

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00:13:14,479 --> 00:13:15,880
and deposit a 1000 dollars.

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00:13:16,310 --> 00:13:18,470
You can see that that's
successful all the way through.

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00:13:19,630 --> 00:13:23,630
You can also see that we've
got the bonus coming in here.

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00:13:23,630 --> 00:13:25,900
So finally, we withdraw 3000
dollars from each account.

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00:13:26,330 --> 00:13:29,319
The first two will fail
the first one because we

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00:13:29,319 --> 00:13:30,564
don't have sufficient funds.

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00:13:31,060 --> 00:13:34,840
The second one because we
are exceeding our 20% limit.

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00:13:35,640 --> 00:13:37,900
But the third and fourth
one are no problem at all.

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00:13:37,900 --> 00:13:41,389
You notice the withdrawals here
are now one whereas the withdrawals

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00:13:41,400 --> 00:13:42,900
on the failed ones are 0.

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00:13:44,440 --> 00:13:47,220
And then what I'm doing is
I'm just calling that same

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00:13:47,220 --> 00:13:49,240
withdraw function 5 times.

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00:13:49,530 --> 00:13:51,550
So there's 1's right here.

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00:13:51,690 --> 00:13:54,709
You can see the number of withdrawals
increasing and increasing and

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00:13:54,710 --> 00:13:58,500
finally, everything fails as we
expect right here

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00:13:58,500 --> 00:14:02,500
because we've exceeded the 3 withdrawals.

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00:14:02,900 --> 00:14:04,230
Okay, so that's it.

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00:14:04,340 --> 00:14:07,520
I'm sure your solution is different
from mine, and that's okay.

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00:14:08,250 --> 00:14:10,290
Take a look at my solution,
maybe yours is better.

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00:14:10,290 --> 00:14:11,349
If it's better, post it.

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00:14:11,660 --> 00:14:15,300
If you find a bug in mine, let me know
please, and I'll be glad to fix it.

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00:14:15,510 --> 00:14:17,310
So I hope you enjoyed this challenge.

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00:14:17,310 --> 00:14:19,180
I hope you understand a
lot about inheritance.

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00:14:19,820 --> 00:14:23,300
In the next section, we're going to
crank up the level in inheritance, and

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we're going to talk about polymorphic
functions with inheritance and that's

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00:14:27,660 --> 00:14:29,400
going to make all of this even easier.

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So stay tuned for that.