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Part 1: Create the Class
4:01We're going to be creating a class that will approximate a bank account. In this first video, we'll lay the groundwork for our program and define the class and an internal variable.
[MUSIC]
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So far we've learned about how to write
classes and methods.
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We've also learned about the different
kinds of variables we can use in
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our classes.
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Let's put it all together and write the
simple bank account class.
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We're going to be using all of the classes
we've learned about so far.
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String, numbers, arrays and more.
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We'll be doing all of this inside
workspaces, so let's get to it.
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Okay, so let's go ahead and create our
bank account class.
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So, let's go to the File > New File.
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We're going to call this bank_account.rb.
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Conventionally, we use all lowercase
letters and
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where there would be a space, we put an
underscore.
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So now, let's write our bank account
class.
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We start out by defining a class using the
class keyword.
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And then, we type the name of the class
that we want.
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In this case, it's BankAccount.
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[BLANK_AUDIO]
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When naming classes, we have to
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have a capital letter as the first part of
the class name.
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And then, if we have more than one word in
the class name,
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like we do with BankAccount, we make that
second word have a capital letter as well.
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This isn't strictly necessary, but
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it is how a lot of Ruby programmers write
Ruby code.
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So it's important to follow these
conventions.
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Now, let's go ahead and define the
initialize method,
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which gets called when we instantiate our
class.
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Now let's think a little bit about what we
need inside of a bank account.
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We need to know who the account belongs
to.
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So, let's go ahead and have a name
attribute in our bank account.
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And we'll send that in when we create the
account.
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[SOUND] Now, our bank account is
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also going to have transactions.
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The transactions are going to be all of
the debits and
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credits that occur on the account.
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We can use an array to take care of
holding that information.
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Therefore, when we start this bank
account,
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let's go ahead and create an empty array
of transactions.
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Now let's go ahead and initialize our bank
account and see what it looks like.
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[SOUND] And let's go ahead and
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print out the bank account instance now.
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And run inspect on it just to see what it
looks like.
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[SOUND] Okay, we can see we have a new
BankAccount class,
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has a name, and an empty array of
transactions.
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So what we've done here, is we instantiate
a new instance of
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the BankAccount class and assign it
to this bank_account variable.
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When we define this method,
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the initialize method, this gets called
when we instantiate the instance.
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So calling new will instantiate an
instance of the bank account and
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run this method.
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We defined an argument called name here
which we set to an instance variable.
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Therefore, we have to send in a name when
we
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instantiate the new instance of the bank
account.
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We then have an empty array of
transactions which we will begin to
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fill out in the next video.
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