Ruby Programming Tutorial - 16 - unless Video Lecture - Introduction

alright guys welcome back why the heck
are you still watching these videos I
have no idea I'm just kidding welcome
back to your 16th Ruby tutorial and in
this lesson I want to talk to you guys
about the or operator and also the
unless keyword weird huh whoa you guys
are going to understand what I'm talking
about
after these videos so basically you know
how I said that you use the double
ampersand and and whenever you want to
test more than one condition and you
want to see if both of these conditions
are true well what if you only wanted to
make sure that one of these tests was
true so you know in the last case if we
had one true and the other one was false
then the code wouldn't run because this
one was false but with the or operator
and by the way the or operator is the
double pipes
I said pipe the double pipe signs and
this is the key if you hold shift and
type the key above enter on your
keyboard
it's that straight up and down line it's
not like a l or anything like that what
this is going to do is it's going to run
multiple tests and as long as one of
them is true then it's going to run the
code so let's go ahead and take a look
at this let's go ahead and say that a
person's weight is 54 they must be
anorexic or something I don't know but
we want to make a program that says okay
we want to check if a person's weight is
less than 100 because if you weigh less
than andra pounds then you need to go
see a doctor or if you weigh more than
500 pounds then you also need to go see
a doctor if you're between 100 and 500
pounds then you're probably good I mean
if you're like 450 then you know you're
cutting it close but anyways we're going
to say that 100 to 500 pounds is the
healthy weight range so let's go ahead
and make a program that people can input
their weight and we can tell them
whether they need to see a doctor or not
so puts you need to see a
dr. if not only does weight have to be
less than 100 or weight is greater than
500 so take note that we are no longer
using that double ampersand ampersand
sign we're using the two pipe signals
and the two pipe I call them signals
when I mean to say symbols same thing so
basically it's going to take these two
tests and run both is weight less than
100 and is weight greater than 500 if
one of these tests is true then it's
going to run the code so it's going to
say okay is weight greater than 500 no
54 is not greater than 500 okay but is
weight less than 100 well yes their
weight is 54 and that is indeed less
than 100 so we're going to go ahead and
hit enter and it's going to say you need
to see a doctor
so unlike before when both of these
things needed to be true with the or
only one of them needs to be true and
then it outputs the code simple enough
so if we go ahead and have weight in
healthy limit like 200 check it out it's
going to say you need to see a doctor if
your weight is less than 100 and or
excuse me or your weight is greater than
500 so since the weight is greater than
100 and is less than 500 then when we go
ahead and hit enter nothing runs they
are healthy wait what about 200 healthy
way and it's debatable depending on how
tall you are so that is pretty much the
difference between or and and whenever
you use or only one of the testing to be
true whenever you use and both of the
tests need to be true simple enough so
let's move on to the next topic
something called unless so you know how
basically in all of these tutorials well
at least in like the last 3 or whatever
I told you guys about the F keyword now
the F key word is pretty much
self-explanatory it's basically whenever
you want your computer to make a
decision whether or not to run this code
you give it an if statement and then a
couple tests so you say ok print
something out on the screen if this test
is true
simple not but what if you wanted to
test the opposite of if you only want to
run the code if the test is false okay
let's go ahead and look at the example
enough with the wait because wait you
know it's a touchy subject let's go
ahead and you know talk about something
a little more appropriate under age
dating so let's go ahead and say that a
girl is running this program and they
want to run the program to see if
they're eligible to date me
Bucky Roberts so I only have one
criteria when I'm dating girls what is
their age I'm not dating anyone unless
they're greater than eighteen so their
age is 23 a KA dateable aka certain
girls out there give me a call send me a
message but anyways enough of the
creepiness let's go ahead and print out
on the screen I will date you if your
age is greater than 18 now we can write
this in a couple different ways let's go
ahead and write the easy part first puts
I will date you explanation point you
can go ahead and make if statement if
age is greater than 18 but what we want
to do is we want to use the unless
keyword now remember this the unless
keyword is the opposite of an if
statement so if H is less than 18
whenever we use unless is pretty much
going to do the opposite so if this is
confusing you guys just remember this
whenever you want to make an unless
statement and it's kind of confusing you
guys just read it is an opposite if
statement so unless age is less than 18
just read it like this I will date you
if your age is greater than 18 okay that
makes sense so basically if this test is
false and let's go ahead and look at
this is age less than 18 well 23 is
greater than 18 so this test right here
is actually false so we go ahead and run
this and it runs the code why because
whenever you use unless unless runs the
code when your test is false so why does
this say I will date you again one last
time because this test is false
so one less time to pound in your head
when every use in the if statement is
going to run the code if the test is
true whenever you use an unless
statement it's going to run the code
when the test is false makes sense it
can get kind of confusing at first and
by the way I typically like to stay away
from unless and I typically use if more
often but for the sake of learning
everything in Ruby I needed to show you
guys
so basically we're saying if age is not
greater than 18 then I will date you by
anyways that's enough about me dating
girls until well probably the next
tutorial
oh excuse me I got kennel cough from
working at the kennel all day I'm just
kidding
anyways thank you guys for watching over
to subscribe and me on Google+ yada yada
yada I'll see you next time