Ruby Programming Tutorial - 14 - Decision Making Video Lecture | Introduction to Coding with Ruby - Back-End Programming

alright guys welcome to your fourteenth
Ruby tutorial and in this lesson I want
to talk to you guys about comparison
operators and decision making because
you know what up to this point we making
some pretty simple programs but if you
think about it all we've been making is
basically just a calculator not very
exciting not very smart but the key
thing is with Ruby in not only with a
Ruby but with good computer programs
they do more than just add and multiply
and divide numbers a good computer
program can make a decision it could
look at a test and depending on that
test or depending on the criteria it can
either run this code or that code so
aside from just you know crunching
numbers it can actually have a brain and
decide things so let me go ahead and
show you guys how to do that right now
so say that we wanted to make a program
where the user inputs their weight and
maybe if it's too big or maybe if it's
too small we need to tell them to lose
some weight or eat some or eat some
cheeseburgers or something like that so
let me go ahead and say the weight they
entered was 120 pounds now of course
this is very skinny unless you're like a
five-year-old girl but anyways if
someone has a way of like 120 pounds
then we need to tell them to eat some
cheeseburgers so we say this we got a
variable called weight and it's equal to
120 pounds now let me show you guys a
simple comparison operator in a simple
way that Ruby can make decisions we're
going to say puts you need to eat can I
spell eat dat there I go some
cheeseburgers and by the way did you
guys ever try Five Guys Burgers and
Fries
it is delicious I shoulda tried it for
the first time about a week ago if you
never tried it before out highly
recommend it okay so what we're going to
say is puts you need to eat some
cheeseburgers and if we just go ahead
and enter now is just going to write
that on the screen no matter what but we
don't want to write this on the screen
no matter what we only want to write you
need to eat some cheeseburgers if your
weight is less than 150
so basically we're saying okay write
this on the screen but only write it on
the screen if the weight is less than
150 because if you weigh less than 150
then you're going to need to eat
something if you weigh more than 150
then you're fine you're healthy so we're
going to go ahead and hit enter and
check it out it writes you need to eat
some cheeseburgers
because weight was 120 and 120 is less
than 150 so just remember this whenever
you want to make a simple test in Ruby
use the keyword if now after if you
write a simple condition or expression
and basically I'm going to say this it's
called a condition or expression but I
just call it a test now there's a bunch
of different things like greater than
less than equals 2 I'm going to show you
later but this is a very simple test you
take a variable and see if it's less
than a number if the variable is less
than the number then this test is true
in the code runs if the variable is more
than well I'll show you guys so say that
weight is now equal to 600 okay well now
we run our test again and by the way for
those of you who don't know what I'm
doing if you hit up on your keyboard
then it just cycles through your
previous statements so check it out we
now set the weight equal to 600 so it
overrides the old value of 120 so now
the weight is greater than 150 so this
test is no longer true we only want to
run this code if the weight is great or
excuse me if the weight is less than 150
now that they weigh more than 150 we
don't need to say you need to eat some
cheeseburgers so go ahead and hit enter
and look at this unlike last time where
outputted you need to eat some
cheeseburgers it doesn't output anything
anymore
so just remember that in order to make a
simple test right if and then your test
if the test is true then your code is
going to run if your test is false which
is in this case 600 is not less than 150
it's greater than 150 that is why our
code doesn't run because our test was
false instead of true so that is how you
do a simple
test and in the next tutorial what I'm
going to do is I'm going to talk to you
guys about all the different types of
comparison operators and also show you
guys how to test more than one condition
at once so that's what we have to look
forward to thank you guys for watching
and I'll see you next time