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Welcome back to the section 16 challenge solution.

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This is part one of the solution to this challenge.

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This was a very, very challenging exercise.

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I hope you're able to finish this, and I hope your solution worked.

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As usual, your solution could be different from mine, very likely it is.

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So let's get started.

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First thing we want to do is we want to make this account class and abstract class.

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And we know that we can do that with the pure virtual functions.

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So that's what I'm going to do right here.

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I'm coming down right here to my deposit withdrawal

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functions. And I'm going to say virtual,

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and I'm going to make it pure virtual, right there.

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My class is now abstract. I'm going to do for both of them.

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And again, I've got a pure virtual function here as well.

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Okay. So that was easy, right. That's cool.

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Eventually, we'll get rid of this guy, and we'll replace it with the printable

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interface, but we'll leave that for later.

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So we've got those two pure virtual functions.

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So if I try to create an account object, I won't be able to any longer.

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So let's take a look at the account implementation file

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and see if there's anything in here we need to change. Our constructors are fine.

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You might be thinking why do I need a constructor if I'm never going to create these things.

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Well, you are, right. You are through the derived classes.

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Remember, the constructor calling up the chain. So it's important that we have constructors here.

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There's our deposit, and there's a withdrawal.

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Now these are pure virtual functions, can we implement them?

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Absolutely, we can. In this case, it makes sense.

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We've got a really simple deposit, really simple withdrawal.

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In the case of the examples I gave you with the shape and you know how do you draw a shape in the

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in the base class, you really can't. But here, we can say that deposit and withdraw,

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this is the simplest case.

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And I'd argue that we would leave this in here. Now there's one little thing that's missing,

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that's our virtual destructor. That's really important. So let's do that.

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We'll say virtual. The destructor is the name of the class with utility in front,

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and we could implement this thing or we could just simply say equals default.

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And that's good enough. That tells the compiler hey just give me

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a default for destructor in this case, and that's fine.

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I don't need any special behavior in the destructor, so that would be just fine.

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All right. So now what are we going to do next.

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Let's look at one of the derived classes. So let's start with checking.

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So let's look at the header file for checking account.

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You see here it's derived from account, that's fine.

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So remember, I've got two pure virtual functions in my parent that I need to implement here.

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So I'm implementing one of them right here. So

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I want to make sure that this is virtual, and i want to be sure that I'm overwriting this

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that way the compiler is going to help me out if I rename something correctly or if I change

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one of the parameters or something.

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Now what about this guy, this deposit method.

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We want to implement this guy in here ourselves as well.

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So we'll just say virtual

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bool,

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and this is the deposit method.

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So we're going to implement this ourselves, and it expects to double.

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And again,

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I'm overwriting here. So I want to be sure that the compiler is helping me.

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Okay. Perfect. What else do I need here, you guessed it.

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I need a virtual destructor for a checking account.

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And I'm going to let the compiler give me a default version,

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which is fine. Okay. Now

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this guy wasn't here before, so we're definitely going to have to implement that in the

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cpp file.

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So let's go into our cpp file for checking account.

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And here's our withdrawal. We're calling our parents withdrawal, which is fine.

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Here's our constructor that looks good as well.

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Again, these output operators will get rid of them later.

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But we need to implement this guy,

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our deposit. And it's going to be a checking account deposit.

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That's the class we're in.

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We don't need the override here.

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We already have it in our header file.

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And we do need a name for this parameter.

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So what do we do here. Well,

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we're simply going to return and call our accounts

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deposit method and pass in the double.

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That's it, right. I have nothing special to do here so I'm just calling my parent.

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So that takes care of checking account.

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Now let's go down to savings account, and we did put the destructor in there right. Yes, we did.

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So let's go to savings account,

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same idea here. We've got

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a virtual function here that we're going to override,

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that's my deposit.

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And we'll say override right here, and then we've got the withdrawal. So I also want to

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take care of that one here. So I'll say bool. We'll call this withdraw,

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and it expects that double amount.

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And again, we're overriding.

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This is one we'll have to implement because we were not implementing it before.

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And then we also need a

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virtual destructor here,

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and the name of the class is savings account,

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let the compiler give us one by default.

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Okay. Now this withdraw method is the one we have to write.

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So let's go to our implementation. So I'm opening up savings cpp.

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My constructor looks fine. My deposit looks fine.

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We'll get rid of the insertion operator later. But

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let's implement this method here.

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So this is bool for a savings account.

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And all we are doing here -- again,

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we don't need the override here only in the declaration.

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And what we're doing here is we're just simply returning our parent, which is the account,

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and we're asking it to withdraw that amount.

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That's it.

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And then the last one we've got is the trust account. So let me go to its header file.

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And let's see what we've got here,

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we already have deposit and withdraw. That's good. We've already implemented them.

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So let's just be sure that we implemented them correctly. And we didn't just

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that we are overriding them and not redefining them.

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So we'll put override over here

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as well as on the withdrawal.

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Okay. That's it.

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Let's take a look at the cpp file.

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All that looks good.

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And the last thing we need here is our destructor.

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So we'll create a virtual destructor for our trust account.

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And let the compiler give us one.

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All right. So that's the first step. So now let's go to our main.

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And you'll notice I commented out all the driver code that I provided for you. So I just want to start

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really fresh here.

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And the first thing I want to do is let's just do this right here. Let's just create an account

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and call it Joe, real simple. Let's build and run.

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And we have an error.

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I forgot a semicolon there, so let's try that again.

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And I spelled the virtual wrong.

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Okay. Let's get all those errors out of the way.

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There's account Joe, finally.

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So now we have a clean compile, and it says variable Joe

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is abstract. You can't abstract. I can't do this. So this is good,

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right. This is a real good thing. We now know that our account class is abstract,

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we can't create any.

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So let's comment that out, and let's create a checking account.

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Remember, this is not using a base class pointer, this is just a regular old

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local variable.

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And we're going to create a checking account.And let's just use the default.

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So now let's test this out. We've created the c object, which is just a checking account.

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And let's display that and see what we get.

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Now this should still work because we overloaded those insertion operators

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when we did this previously.

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And as long as we're not coming at, this with a base class pointer. They should all still work.

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So let's try that out. And let's see what we get.

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There we go. We've got a checking account, unnamed checking account

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with a 0 balance. That's exactly what we expected.

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So let's create a savings account object,

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and we'll call it s. And we'll initialize it to Frank

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with 5000 dollar balance and

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2.6% interest.

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And let's display that and see what it looks like.

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All right. Let's try that out.

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Here we go. We've got a savings account object Frank 5000 2.6, perfect.

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So this all seems to be working perfectly.

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So now why don't we create a base class pointer.

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So the base class is the account class, right.

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So we'll create a pointer called ptr.

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And let's create a new trust account.

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So we'll create a new trust account on the heap, and that will be let's say Leo

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with 10000 dollar balance and 2.6% interest.

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So that should create that object on the heap, and the pointer will point to it.

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This was perfectly valid since a trust account is an account.

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Now let's display that and see what we get. Now we can't display ptr here

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because that will display the address of that pointer.We need to display the object.

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So we need to de-reference ptr. We need to go to where ptr is pointing and an endline here.

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and an endline here.

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Now this won't work as we expect.

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The reason is we haven't really handled

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the insertion operator to work with dynamic polymorphism.

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So as far as the compiler is concerned,

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that insertion operator -- compiler knows that ptr is a pointer to an account,

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it really doesn't care what type of account it's pointing to. So it's going to bind this statically,

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and it'll slice that object. It'll slice the trust account stuff away

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and just keep the account part.

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So this should still display Leo in 10000 though

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because all accounts have the name of their balance. So let's give that a try

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and see what our output is, and that's exactly what happens. You see right here,

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account Leo 10000.

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We're not getting the trust part of us, right.

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It's not even displaying trust account, it's just displaying your account.

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We'll fix that when we implement that i printable interface, that'll be pretty cool.

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So we can see that this seems to be working. Let's test this out.

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And let's just test it out with s right here. Let me comment out this Leo part here.

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And let's just say that we want to deposit,

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let's say,

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10000 dollars into s.

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And then I want to display s again.

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So let's try that out. And you can see here,

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I have my savings account Frank with 5000, and I just deposited 10000 into it.

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It's a savings account, so it's going to use that interest rate to give me a little bonus. And that's exactly what happened.

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So that looks correct. And then finally, let's withdraw.

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So now let's say we want to withdraw

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10000 dollars from s.

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And again, we'll display s.

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And we'll test out our withdrawal functionality here.

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We'll give it a run. And we can see that we have

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savings account 5000, then we deposited 10000,

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and then we withdrew 10000. So it's all looking good.

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So you see it wasn't too much work to get this to work with

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dynamic polymorphism. The next step now is

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let's get rid of all the overloaded insertion operators that's in this code.

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And let's create that printable interface and get that working.

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And then the last thing we'll do is

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we'll take care of those functions in the account util file

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and clean that up because there's a lot of duplicated code in there.