Objective-C Tutorial - Lesson 13: Part 1: Extending Your Program Video Lecture | Learn and Understand: Objective C (English) - Web Development

what is up guys jordan here with
Objective C toros lesson 13 extending
your program and this lesson will be a
little bit different because we actually
won't have a keynote that is right we
know everything that we need to know for
this lesson so we won't be learning
really anything new per se I will be
going over a few new aspects of things
that we have talked about but we're just
really going to be extending our program
and really making it easy to extend and
add features in the future as well as
right now so let's go ahead and jump
right into it now since this is a
vacation budget and you don't just
vacation in one country you may want to
add different budgets for each of the
different countries that you may be
going to so there's really two ways of
doing this the first would be to simply
add a budget here for every time you go
to another country so let's say we're
going to be going to England and then
you copy and paste these functions and
then you replace this with the country
and then of course you add in all the
information up here and you pretty much
just retype the entire program every
single time you need to add new country
now that may be very simple and easy
let's say if you're going to only add
three countries in the whole program but
if you're going to be extending it in
the future and whenever you extend the
program and now you always want to be
looking into the future of how easy will
be the next time you want to extend it
even further so that really wouldn't be
a same approach right now because it
would be very messy and complicating
easy to mess up in the future when
you're adding let's say five ten
countries to this program not that you
necessarily would but you never know you
always want to make it easy to extend so
the more st. approach would be if you
simply added an argument that could
handle one of these struct variables so
if you simply typed in budget and then
I'm just going to do either budget as
the variable name and then put either
budget right here this would allow it so
every time all you have to do is edit in
maine and because this can take either
budget you it could send it vacation
budget or vacation budget england so
it's easy to extend when adding other
countries so now up here i'm just going
to add the budget that i'm actually
going to be using and then up here and
spend dollars budget either budget and
let's build and run save all
okay so everything built and Iran
correctly but oh what is that yes that
says a thousand dollars why in the world
is this a thousand dollars well if you
remember when we went over functions a
few lessons ago whenever you use an
argument it is copied so right here
vacation budget the budget since it's
part of the argument now it is copied so
it copies a thousand dollars so it's not
actually using anything from down here
when I had the operations done on it on
spend dollars it's just a copy of it
right here that's all you're using so
since that's the case it doesn't look
like this would work out but you're
forgetting something very important
pointers now even though we've gone over
pointers before we really haven't used
them quite in this way so the first
thing I'm going to go over is the main
thing that we want to get access to is
we want to get the address of the budget
whatever budget is that we're going to
be using because when you get the
address of this budget whether it's the
budget for England Spain Brazil whatever
the country is you then get access to
all the members inside so we're working
with just vacation budget right now so
use the + sign remember because that
gives us the address and then we're
going to be giving that address we're
going to be passing it to the arguments
down here so we use the deference
operator and when you have when you work
with objects or structures and they have
members you use a different type of
deference operator you use kind of this
error looking one which is dash and then
the greater son so it's kind of like
either budget and then pointing inside
to the budget
and then of course make sure in the
function prototype that you mimic
exactly what you typed right here
otherwise you'll have some problems and
then you can build and run and save all
now everything worked fine so now that
we really understand what we need to do
to extend this program we're going to be
adding an England budget and then one
for Europe so we're going to be changing
some names around and then we're going
to be adding a whole nother budget and
everything so let's get to it