Objective-C Tutorial - Lesson 28: Part 1: Setting Up for the Switch Statement Video Lecture | Learn and Understand: Objective C (English) - Web Development

what's up guys john here with Objective
C tutorials lesson 28 part 1 setting up
for the switch statement and in this
lesson we actually won't be coding the
switch statement like the name the
lesson says we'll just be setting up
word and then in part two will actually
be coding this switch statement now to
start off this lesson let's go over some
of the problems with our program right
now now in previous lessons we only used
an array for one of the transaction
types that was spend dollars now if we
wanted to extend this functionality to
each transaction type or every country
we need to create a new array for each
transaction type for every country now
you can see this would get a very messy
and way too many lines of code when we
start adding more and more countries to
our program and possibly new transaction
types as well now what we really need is
just a single array that can hold the
different transaction types for all the
countries and that's what we'll be
working on in this lesson and in future
lessons now what are some of the
solutions well in future lessons will be
using object-oriented features such as
inheritance and polymorphism and I'll
get into both of those in future lessons
but in this lesson it'll be more of a
quick fix solution will be using a
switch statement and we'll still need an
array for each country but we'll be able
to store both charge and credit
transactions in one array and will also
change the transaction object from a
rapper to a real object and what I mean
by real object is one with I bars and
methods and you may be saying well
what's a rapper no I'm not talking about
Eminem or somebody that wraps presents
at Christmas time yes those are rappers
but when i say rapper here i'm meaning
an object that is mainly used to change
something into an object and NS number
is a great example of this NS number
just changes a regular number so let's
say fourteen into an object so basically
NS number it's just putting the number
fourteen into a boxes as this is an
object and then the program looks at it
and says oh look that's an object but
it's really not truly an object in the
respect of it doesn't have I bars and
methods but the program still looks at
it
as an object now some of the specifics
about the coding in this lesson we've
already learned in previous lessons
everything that we need to know to code
the transaction class that's what we'll
be doing in part 1 and in part 2 of this
lesson I'll cover the switch statement
but in this lesson or in this part of
lesson 28 will just be setting up for
the switch statement so anyways let's go
ahead and jump into Xcode and code up
the transaction class okay so here we
are in Xcode and we'll be working with
the same program that we've been working
with for the past I don't know how many
ever lessons but before we actually get
into coding the transaction class we can
actually clean up the code a little bit
we've been testing out some numbered
things and we can go ahead and delete
them so this NS log here that was just
test something out and then the CRA that
was test something out and delete those
then down here all the arrays and arrays
stuff that we practice last lesson you
can delete that so that cleans up the
main function quite a bit so you can go
ahead and save that then select the
classes folder because this is where
this new transaction class will go then
go up to Xcode menu bar go to file new
file and then under mac OS x on select
cocoa class then objective c class make
sure it's the subclass of NS object then
hit next then name it transaction dot m
then have checked the box that says also
create transaction h make sure that's in
the right location then finish now it'll
create this new class and then go into
transaction dot h now the first thing
we're going to do is we're going to use
something called a typedef and we went
over type deaths and enumerations in
lesson 11 part 2 so if you're a little
shady on that don't really remember what
all they are make sure and go ahead and
look over that lesson right now and then
come back to this one but if you do know
what they are continue with the lesson
so first type
and remember that this creates a new
type so instead of saying like int or
whatever you can say your own little
data type so typedef and then
enumeration so then we're going to be
creating some variables and these
variables cash and charge they're both
integers automatically because it's an
enumeration and then the name of this
new type will be transaction type so now
we can jump inside the interface and
we're now going to be declaring our
first I bar type and it's going to be of
it's going to be of the type transaction
type and then and create a double call
it amount so and then we're going to
create some methods so void create
transaction and remember create
transaction is just the name of the
method and the argument is going to be a
double the amount then of type is
another part of the name so this will be
void created transaction of type as the
name of the method and then the argument
the type will be transaction type a type
then this will be of type double return
amount then this will be of type
transaction type
return type so we're all done coding up
the interface just remember whenever
we're saying transaction type is really
like we're saying into cash and in
charge so anyways now we jump into dot M
will make sure you go ahead and save
that whoops got to have your cursor in
without the code save anyways then go in
g dot m now alright so the first thing
we can do is void create transaction and
that whole thing automatically pops out
there for us and then type equals a type
and amount equals or really is the
amount so now we're just assigning the
values the I bars we're assigning them
to the arguments that's all we're doing
right here then down here with double
return amount really simple return
amount and that's the ibar amount then
this one transaction type return type
very simple again you just return type
and then close that out go ahead and
save and if you build and run it'll take
a little while and then as you can see
there's no new results it looks a little
bit different just because it's smaller
because we deleted all that extra stuff
that we don't need anymore but there's
actually no new functionality that we
added in the program just the
transaction class but like I said we
didn't implement any new functionality
will be doing all that in part two of
this
than using the switch statement so be on
lookout for that coming up next weekend
and follow me on Twitter and Facebook to
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