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If the condition of an if statement is
false, the code in its body won't run.

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00:00:05,160 --> 00:00:09,980
Here, we set the if_condition variable
to equal the false Boolean value.

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00:00:09,980 --> 00:00:13,620
And since that's our condition for
this if statement, and

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that's false, the code here doesn't run,
and we have no output down below.

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If you have some code that you want to
run when the if statement doesn't run,

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you can add an else clause.

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You add the keyword else between if and
end, followed by one or

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more lines of code that you want to run
instead of the if statement's code.

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So here we'll call puts, and
we'll pass it the string else clause.

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Ruby doesn't require it, but
it's conventional to have the else keyword

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aligned with the if keyword, and
the else code indented one level.

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Again, it just makes
the code easier to read.

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Let's save this, and try running it.

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00:00:58,300 --> 00:01:02,950
And this time because the if clause is
false, the else clause runs instead, and

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it prints else clause in our output.

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If we were to change
the if_condition variable to true,

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And try running it again,
then the if clause will run, and

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we'll see if clause in our program output.

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But let's change this back to false.

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If you have other conditions that you want
to test only when the if_condition is

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false, you can add one or more elsif
clauses between the if and else clauses.

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You add the keyword elsif,
another condition expression.

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So we'll test the value of
the variable elsif_condition,

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which we'll define in a moment.

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And some code you want to run
if the condition is true.

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So we'll say puts elsif_clause to show
that the elsif clause is running.

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Then up here,
let's add an elsif_condition variable.

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And we'll set this to true.

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Let's try running this again.

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And because our if_condition is false and

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our elsif_condition is true,
the elsif clause is what runs down here.

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As with the else clause, the elsif keyword
should be lined up with the if keyword,

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and the code following it
should be indented one level.

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Now what if our if_condition
variable were set to true?

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Let's try running that.

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If the if clause is true,
then neither the elsif clauses nor

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the else clause will be run.

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What if we were to set both if_condition
and elsif_condition to false?

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Let's try running that.

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If the if_condition and
all elsif_conditions are false,

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then the else clause will be run.

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The else clause isn't required,
if all conditions are false and

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there's no else clause,
then no code will be run.

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Let's apply what we've learned
to the widget store program.

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Right now, we're checking the conditions
for all three if statements.

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We've tried to fix it so
this won't happen.

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But if more than one condition were true,

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the price_per_unit variable would
be set and then overwritten.

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No matter what we only want
price_per_unit set once.

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Let's use elsif and
else clauses to clean this up.

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So, we're going to combine all
this into one if statement.

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So, we're going to get rid
of these end keywords here.

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And we're going to convert
these if statements to an elsif

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statement and an else clause.

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But really the elsif branch can't possibly
run if the quantity is equal to or

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greater than 100 because then
only the if branch will run.

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So we can get rid of the Boolean and
operator and the second comparison.

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So let's save that and
try running it ruby widgets.rb.

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We'll try running it with a quantity
of 100, and it's multiplied by 8.

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Let's try running it again with a quantity
of 50, and it's multiplied by 9.

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00:04:07,921 --> 00:04:13,361
And let's try running it with a quantity
of less than 50, we'll go with 10,

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and it's multiplied by the full price,
$10 per widget.

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Our both discount features working great.

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Thanks to the elsif and else clauses,

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we can be sure that the discount
is applied only once.

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We've completed all of our features.

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We display a welcome message to our user.

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We prompt them for
the number of widgets they want.

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And store it with the [INAUDIBLE] or
in a variable.

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Then we calculate a total price for
the order.

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We also apply a discount if they're
ordering 50 or more widgets.

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Our program is done.