Objective-C Tutorial - Lesson 23: Part 2: Coding the NSMutable Array Video Lecture | Learn and Understand: Objective C (English) - Web Development

okay so here we are in Xcode and what
all we're going to be doing is we're
going to replace this NS number object
here and we're gonna replace it with two
new NS number objects and then we're
gonna add it to a new NS mutable array
that we're gonna create we're gonna add
those two objects to that array and then
we're gonna pass those two objects from
that array through the spend dollars
method in two different ways and then
we're gonna do a little other bit of
tweaking to our program along the way so
we have a lot to do and this will be a
little bit longer of a coding video but
let's go ahead and get to it so the
first thing you can do is you can just
delete that old number of dollars in
Europe and what we're gonna name the new
ones so we're gonna name them they're
still going to be NS numbers and
everything but we're gonna name them
Europe dollar transaction and then we're
gonna go coups NS number and we're gonna
allocate some memory initialize it with
the double value of 100 and then we're
gonna create another one name that
Europe dollar transaction two
then we're gonna allocate some memory
and initialize this one with the value
of 200 okie dokie now we're gonna create
an NS mutable array and like I went over
and ki know it's bits it's the same
basic setup that you've been used to for
creating objects and hold on wait before
I actually create that NS mutable array
I forgot to put the asterisks in here so
you always have to have asterisks
because you're always creating a pointer
to the object not the actual object same
thing NS mutable array a strict Europe
transactions equals NS mutable array and
then we're gonna allocate some memory
and initialize it with the capacity of
one even though we're gonna put two
objects in it I'm gonna initialize it
with the capacity of one just to show
you how the NS mutable array is truly
mutable no to adding objects how do you
add these well I went over this but if
you kind of forgot um since you saw the
keynote you specify which array then the
add object message and then which
objects you'd like to add this case
Europe dollar transaction and then
Europe transactions add object which one
Europe Europe dollar transaction to okay
so now we've created these two objects
and created this mutable array and then
we've added the two new objects to the
array no that's all great but how do we
really get access to these objects once
they're in this array to pass through
this spend dollars method here well the
first one we're gonna use we're going to
be using the index of the array and
that's one of the cool things about the
array everything's at index and if you
remember this first thing would be at
index zero and the second one would be
at index one because the index starts
counting at zero
not at 1:00 so remember that that can
trip up a lot of people if you don't
really remember that okay now the first
thing we're gonna do is we just need one
bracket here and then Europe
transactions so you specify the array
then the object at index of zero and
there we go so we can do this again here
you're at budget spend dollars and we're
gonna pass through the object at index 1
in this spend dollars message so if we
build and run everything should go and
run correctly okay now there is a little
glitch that I forgot I only closed it
out with one bracket you need to because
I forgot to close out that front one and
then I close out this last little
statement here so then we can save all
and now it build and ran correctly and
as you can see we have two hundred
dollar value while we actually have
first a hundred dollar value and then we
have a two hundred dollar value there
just like what we told the program to do
now what we're gonna do is I'm gonna go
back to the implementation the header
file and show you something right here
you would usually have to say that this
is a double value but we didn't have to
because back here in the implementation
we already said that it was a double
value it was Anna snubber and all that
and in the header as well now there's
one little thing I wanted to go over
that I didn't go over last lesson I
should have right here the type as you
know you put the type inside parentheses
um that type here is NS number but you
see this asterisk you may be saying why
do we have to have that asterisk well
let me jump up here and kind of explain
something if we're gonna declare this as
a variable we'd say double then space a
budget equals and then assign of value
to it if we were going to do the same
thing for this we would say NS number a
strict then dollars so NS number a
strict the asterisk is really just kind
of included as part of the type here
because you're always going to need that
astrick whenever you're declaring an NS
number or really any type of object
you're always pointing to that objects
you're not actually declaring that
object directly so that's why you have
to have that asterisk there and then
down here of course saying what type of
an NS number so NS number is the main
type but then double values that type
within the type so we're gonna replace
all this with double and put it back to
how it was before last lesson so we can
just take out all this double value
stuff and down here and there we go now
we need to do it in the header file as
well and there we go
no we can jump back to our main file
here and we will need to say at the end
of this that this is a double base so
put one bracket here and then right
after one bracket just put double value
and it's kind of confusing like we're
all to put the brackets and everything
when you're coming in and doing this
later when I was getting ready for
recording this side quite a problem I
got all mixed up where to put the
brackets and stuff it's a whole lot
easier when you do it the first time
when you go back and add in stuff make
it's kind of hard but also those spend
dollars are fine but we also need change
in this spend dollars because
back here in the implementation and the
header files before we had said that
this was a double value and this as you
remember is an nsnumber
so we have to specify that's a double
value because we took out all that stuff
so add a little bracket in front there
then say it's a double value and then
close it off with one and then we're all
good to go so built and run save all and
everything build and ran correctly so as
you can see same results as before we
weren't expecting anything different
just a different way of doing it in the
program okay now we're going to use a
little bit different method to pass
these two objects in this NS mutable
array through the spend dollars method
so you can just delete right here well
we just typed and what we're going to be
using is that we're gonna be using an
enumeration the for n which is a spinoff
if you're a member of the for loop and
how it goes is it starts off with four
and this says like collect everything
and place it in this NS number that
we're gonna create here called a
transaction so collect everything and
place it in and pass it through this a
transaction everything that's in and
then you specify which array and that is
Europe transactions no you put a little
curly brace and then you put the
statements and the statement will be
Europe budget spend dollars
then put a little bracket a transaction
then double bay and close it all off and
then with the curly brace of course we
wouldn't have to put double value here
if we hadn't changed all that stuff in
the implementation header file that we
just changed but we did change the say
after but double value um again let me
just run through this one more time
don't want to end up rambling about this
but for says collect everything I had
every item and pass it through this
object that we just created and
everything in the Europe transaction it
will pass through this NS number so
right here this says that it's a for for
in enumeration this creates the object
that it everything will be passed
through one by one and this specifies
which array is being accessed to get all
the information so let's build and run
save all and there we go everything
built and ran correctly as you can see
the hundred dollars two hundred dollars
everything so this is kind of a tricky a
little bit more of a tricky concept to
understand maybe then most things we've
been going over so far but really a cool
cool concept because instead of having
multiple lines of code because if you
did that index thing where you have to
specify each index I mean that's gonna
take a lot of times it's really you know
pointing using an array if you're gonna
do all that but this is really why in a
race so so useful you just throw all the
information into the array that you pass
it through one object and then you place
that object as the argument and then
you're all good to go
so a really really cool feature that's
NS mutable arrays in objective-c now
you have any questions or comments or
anything just tell me about them in the
comment section below I'll do my best to
get back to them but I'm kind of busy
sometimes you know at school and just
life also if you like this video please
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and liking these videos um the next
lesson we'll be going over just NS
arrays they're not mutable they're just
fixed or raised and then after that I'm
not sure we may be going over the
debugger or maybe going something even
more but that's a little ways down the
road but yeah thanks for watching and
check out some my other videos if you
haven't already and I'll see you in the
next one later