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Let's get back to our
Widget Store program.

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We're still working on asking the user
how many widgets they want to order and

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storing the number they enter.

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Now that we know how to write methods and
pass arguments to them,

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we know most of what we
need to add this feature.

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Let's give it a try now.

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We'll define a new ask
method that takes a question

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parameter in the form of a string.

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Make sure to type an end keyword
to end your method definition.

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And for now let's simply call the print
method within the ask method body and

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pass it the question,
we got as a parameter.

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And following our welcome
to the widget store method,

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let's make a call to this new ask method.

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We'll call ask and then here in
parentheses we'll pass a string.

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And in that string, we'll say,
how many widgets are you ordering?

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Let's save that and
try running it with ruby widgets.rb.

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And we can see our output
down here in the terminal.

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As before we've got our welcome
message welcome at the widget store.

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And then here's the results of our
call to the ask method up here.

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We pass it the string how many
widgets are you ordering?

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And that gets printed down here.

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Notice that it's not skipping to a new
line after printing the question that's

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because we're calling the print
method instead of put S method.

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The reason for
that will become clear shortly.

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Now we need to get the text that
the user enters at the keyboard,

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the gets method can do that for us.

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When we call gets it waits for
the user to type something and

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press enter and
then returns what the user types.

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In this version of ask,

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we'll just assign the value the user
typed to a variable answer.

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We'll name our variable answer and we'll
assign it the return value from gets.

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And then we'll simply print that value.

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So we'll save that and try running it.

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And as before, it'll print out
the question that it's asking us.

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How many widgets are you ordering?

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And now it's waiting for
us to type some input in the keyboard.

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And that's why we used a print method to
print the question instead of puts which

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would skip down to the next line.

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Our input is going to appear here
on the same line as the question.

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So now we can type whatever
we want here at the prompt.

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So I'll use a value of 8 and
press Enter when I'm done.

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And the value that I typed will
get returned from the gets method,

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assigned to the answer variable,
and then that will get passed to

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the puts method called down here,
and printed out to the console.

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So we typed 8, and it prints 8.

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So how does this work exactly?

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Well, Ruby methods have a return value,

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a value that they send back
to the code that called them.

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Here, the return value from gets is
getting assigned to the variable answer.

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Let's take a look at return
values in another context though.

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Here are our add and
subtract methods from before.

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First I'm going to get rid of this first
line here, which prints out the parameters

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that they receive cuz we don't
really need that code anymore.

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Now currently the add and subtract methods
just print the result of adding or

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subtracting their first and
second parameters.

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But let's modify these methods so
that they use a return value instead.

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I'm going to remove the call to puts and
then in its place,

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I'm going to use the return keyword.

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Following the return keyword is
an argument that you want to

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return to the method caller.

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So in this case, we'll just use the exact
same code that we did previously.

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We'll add the first and
second parameters and return that value.

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Down here I'll remove the call to puts and
I'll use a return keyword there as well.

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Let's try running this.

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Ruby parameters.rb and we don't get
any output right at first that's

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because the return keyword
doesn't print a value or

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do anything besides pass it back
to the code that called it.

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In order to actually see the output again
we're going to need to do something with

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those return values down here in the place
that we're calling these methods.

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So this call to the add method here is
actually returning a value right now.

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It's calling the result of adding
its first and second parameters.

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But we're not actually doing
anything with that return value.

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So I'm going to take the return value and
pass it to puts method down here.

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If we save that and try running it,

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this time we'll see output.

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We'll see the return value that we're
getting from the add function, 150.

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Let's do the same for
the remaining method calls.

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So puts subtract, puts add, puts subtract.

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Try running it again.

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And this time you can see that all four of
our method calls are returning values and

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then we're printing them out down here.

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We don't actually need
the return keywords here though.

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The last expression evaluated in a method
becomes that method's return value.

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So if we were to remove the return
keyword here, first plus second would be

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the last expression evaluated
within the add method's body, and

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that would become the 
method's return value.

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So let's remove the return
keyword from add, and

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we can remove the return
keyword from subtract as well

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because this expression will be the return
value of the subtract method.

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And if we try running this, it'll behave
in just the same way it did before.

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There's a variety of things you
can do with Ruby return values.

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You can either take the return value and
pass it directly to another

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method as we're doing with puts in
our add and subtract methods here.

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Or you can assign a return value to
a variable first, if you prefer.

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So for example, we can assign
the return value from add here to

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a total variable, and
then print that out if we want.

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Save that, try running it.

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And you can see that the end
result is the same here.

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We take our first call to add.

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Its return value is going to be 150.

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We assign that to the total variable and
then print that out here.

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And you can see a 150 in
our results down here.

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We can also use method return values
as arguments for our own methods.

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So for example, I can take the return
value from calling add 1 and

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2, and I can pass that back to
the add method as an argument.

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So add 1 and 2 will give us three,
we can add 3 and 4 like this.

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Let's try saving that, and running it.

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Whoops, I forgot to call
puts with that return value.

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Let me go back up into the code and
have that there.

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And that's we had no output.

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Let's see if we get output this time.

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There we go.

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The result of adding 1 and 2 is 3, and
the result of adding that to 4 is 7.

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You can see that in the output down here.

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Let's try making another call to add.

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And this time we'll take the number 3 and
we'll add the results of subtracting.

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11 and 7,

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try running that.

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And the results of subtracting 7
from 11 is 4 if we add that to 3,

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the result is 7 again.

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It's very important not to confuse
a method returning a value

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with if printing a value using puts.

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So let's take our subtract method
here and let's pass a variable to it.

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We'll declare a variable named number and
we'll assign it a value of 9.

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We'll print out of the value it contains.

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And then we'll reassign to that variable
the result of calling the subtract method.

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A little typo there, let me correct that.

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And we'll call the subtract method
with the value currently in number.

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And the number 1, which will subtract
1 from whatever's in number and

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assign that back to number.

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So number should contain 8 after this,
and let's copy and

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paste that code so
that we do it again a second time.

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And then with printing the final
value in the number variable.

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Okay, let's try running this.

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And we see 9, 8, 7 as our output.

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We start with 9, subtract 1 and
get 8, subtract 1 again and get 7.

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But suppose that instead of returning
a value, the subtract method

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printed the result of subtracting
its second argument from its first.

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This will actually return an empty
value from the subtract method.

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So lets try running this, and
it appears to work correctly at first.

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It prints out the value and
our number variable 9, and

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then it appears to subtract 1 from it
giving us 8 and printing that out.

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But what's actually happening here,

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is that the call to puts is
returning an empty value.

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And that's what gets assigned to
the number variable down here.

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Then when we try to call subtract with
number, which now contains this empty

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value, we get an undefined method minus
for NilClass, that is an empty value.

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So make sure not to confuse a method
calling puts with returning a value.

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In many cases a method will only work
correctly if it actually returns a value.

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So now that we actually understand
method return values a bit better,

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let's update our ask method to use them.

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Instead of taking the value
return from gets and

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assigning it to a variable and
then printing that variable out,

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let's simply return the user's
input from the ask method.

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We'll assign that return value to
a variable named answer down here.

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And then after that we'll print the value
that the answer variable holds.

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This way we'll be able to do other
things with the user's response out

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here in the main code.

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Let's save then and try running it.

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Ruby widets.rb and it'll ask us
how many widgets are you ordering?

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Let's say 8.

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And as before it will print
the value that we input of 8.

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We've completed the second feature for
our program.

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We ask the user which quantity of widgets
they want, call the gets method to get

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their keyboard entry, and store
the return value from gets in a variable.

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Learning the call methods was the key
to getting this far in your program.

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Practicing your new skills is
important to making them stick.

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So be sure to check the teacher's notes
on this video for some practice ideas.

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You're off to a great start learning Ruby.

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You've learned the call methods and
to use their return values.

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You've even learned to
write your own methods.

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Those skills would be useful in
pretty much every program you write.

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And now, you can also store values
in variables when you need to,

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that's another skill
you'll be using a lot.

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There's just one minor
issue with the program.

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When we ask the user how many
widgets they want to buy,

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our question runs right up against
the place their keyboard input is shown.

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That looks a little
less than professional.

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To fix this, we're going to need
to learn more about strings.

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Just like most other
programming languages,

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Ruby uses strings to store text.

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We'll learn all about
them in the next stage.

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See you there.