Ruby Programming Tutorial - 26 - Decision Making with Regular Expressions Video Lecture | Introduction to Coding with Ruby - Back-End Programming

alright guys welcome to your 26th Ruby
tutorial and in this lesson I want to
finish up talking about regular
expressions at least for now now I need
to talk to you guys about one more topic
involving regular expressions and that's
decision making using regular
expressions so say that you were making
a website and you wanted the user to
sign up with a name and a password and
everything say we're making a website
like Facebook or something where they
need to input their name like Bucky
Roberts well what we could do is we
could test this string which would be
their name and we could see we could
like make sure it didn't include any
weird symbols like dollar signs and I
don't know like numbers or anything so
the first thing we would do is we would
need to make sure that their name didn't
include any numbers like Bucky 67 so
let's go ahead and do that right now
so let's just go ahead and print out on
the screen here Wow I messed that up
already
excellent your name cannot contain
numbers and we want to check if their
name contain numbers so we would go
ahead and write an if statement and now
go ahead and just write a name with a
number in it like Bucky 45 obviously
this can't be someone's name so we want
to test against this using regular
expressions now I'm going to introduce
you guys to a special type of operator
and that's the equal sign in the little
squiggly now it's the very top a left
key on your keyboard in case you never
saw it before
I think it's actually called the tilde I
think they use it in like Mexico or
something I don't know what it's really
is for but what this does in Ruby is
it's used whenever you want to compare
to a regular expression so basically we
want to test for any numbers so make
your regular expression and make your
group from the range 0 to 9 so basically
this is a group 0 to 9 which basically
looks for any number now we're basically
looking for any number in this string
right here and if we find a number in
there string then obviously we need to
give them an error message because you
can't have numbers in your name so go
ahead and hit enter
and our output your name cannot contain
numbers obviously so that is a very
simple way that we can use
decision-making using the equals little
tilde and then giving it a range to
check by now another cool thing that you
can do is you can actually use a method
called match if this today thing is kind
of confusing and this is what I prefer
to do as well so let's go ahead and
think of another example other than
names because I mean the difference
between names and user names can get
kind of confusing so say that we wanted
the user to enter their telephone number
for whatever reason so let's go ahead
and interact something on the screen and
let's say we want to test we want to
make sure that the telephone number that
they give us it doesn't contain letters
because your number can't be like 486
apple-pie 74 just doesn't make sense I'm
sorry so let's go ahead telephone number
can't contain letters exclamation point
so now what we want to do is we want to
use our decision-making skills to go
ahead and finish this function so if and
now and put the phone number like um
four eight six beans and PI 34 that
seems like a nice number to me now
instead of this little equals tilde we
want to use the match method now as a
parameter in the match method we need to
give it a regular expression so again
remember like I said every regular
expression starts and ends with that
forward slash now in between these
forward slashes we need to say okay all
characters so what we can do is we can
give a group of ABCDE no no we learn a
little shortcut and that is just a to z
now this is going to do is it's going to
check that does this string have any
characters in it if so then give them
this error message that's basically all
we're saying here let's go ahead and hit
enter and check it out it says telephone
number cannot contain letters because
this telephone number for a six beans
and pie third
4 does indeed contain a lot of letters
so now let's just go ahead and verify
this by writing an actual real telephone
number so 4 5 4 5 6 3 4 so now check it
out our new telephone number is 4 5 4 5
6 3 4 now even though it contained this
little - right here what we were doing
is we were checking whether it contain
any letters so this is an indeed of
value or what's the word I'm looking for
a valid telephone number there we go I
was about to say valuable this is indeed
a valid telephone number since even
though it contains a - it does not
contain letters so let's go ahead and
hit enter and check it out no error
message whatsoever so there you go
there's the basic concept of how to use
regular expressions in decision-making
again whenever you want to match
assuring against a regular expression to
see if you know maybe it contains any
numbers or letters you can either use
the equals tilde or you can use this
match function now to be honest there
are subtle differences they aren't the
exact same thing but for the concept of
this tutorial I'm just going to say
they're the exact same thing so thank
you guys for watching don't forget to
subscribe and I'll see you guys in the
next video when we are going to be done
talking about regular expressions