Objective-C Tutorial - Lesson 4: Part 1: Increment & Decrement Operators & Comma Operator Video Lecture | Learn and Understand: Objective C (English) - Web Development

what's up guys this is Magnum Peter help
here with objective-c tutorials lesson
for more operators now what all will we
be learning in this lesson we'll be
learning about increment and decrement
operators comma operator cast operator
and sizeof operator now to start off we
have increment and D increment operators
now they look like a plus + or minus -
before after a variable now they
increase or decrease the value stored in
the variable by 1 and the different
possibilities there are a plus plus plus
plus a a minus minus and minus minus a
now when plus plus or minus minus is
after the variable is increased the
variable is increased or decreased after
the expression is evaluated
now when the plus + or minus - is before
the variable it is increased or
decreased before the expression is
evaluated now I know this is kind of
hard to grasp just in text so we'll be
going right into Xcode and I'll be
showing you exactly what this means okay
now go ahead and open up a new Xcode
file like I showed you in lesson 2 or
just open up the one that we've been
working with through the past few
lessons and delete everything and then
clear int a and then set its value to 2
now we're going to set up some NS logs
in this first one we're going to do a
plus + equals and then % I
then we're gonna do a plus I can't type
today plus plus and then we're going to
do NS log a now equals a
and then we're gonna set a back to
and then we're gonna we're gonna declare
another one but this time instead of
doing the plus plus before we're gonna
Herbie said doing it afterwards we're
gonna do it for ya addition comma plus
plus I cannot type today and I slog a
now equals percent I a okay now we're
gonna set in a back to two again then
we're gonna do NS log and now we're
gonna try out a minus minus equals
percent I a - minor it nice - NS log
a now equals
variables a and do a equals to and
remember because we're changing the
value of a every time that's why I keep
on declaring the int a minus minus a and
the last line of code here a there yeah
hey now equals percent I close off the
codes comma a okay now you can save it
and build and run now everything should
oh oh that's the problem here is a very
important bug thing that I messed up on
okay as you can see right here I read it
cleared every variable you don't need to
read eclair the variable you just have
to reset the variable because Hays
aren't declared up there the top so all
you have to do is just a equals two okay
now let's try it again
okay now a plus plus let me look at it
alongside the code here as you can see a
plus plus equals two and a is two so it
doesn't like I said when it's afterwards
it doesn't actually assign that extra
one to the value until after it's
already done that initial equation so
there below it's three then this one is
plus plus a so ends before it signs the
one and then evaluates whatever equation
and of course it's three there and then
a minus - because it's afterwards it
just initialized it does the equation
that initial equation is two and then
afterwards it
attracts the one but when it's before it
subtracts that one before does anything
else and then of course afterwards is
still that one so that's how the
increment and increment operators work
so let's go back to Xcode and learn
about some more operators okay the next
operator is the comma operator now the
comma operator allows you to use two or
more expressions where only one is
expected it evaluates the first operand
usually the first one is always an
expression because it then discards the
results then it evaluates the second
operand in that expression in earnest
about you so as you can see down below
we have variable a and we make it we set
B equals 3 comma B plus 2 in the value
of a so B equals 3 is the first part so
we're actually declaring a variable in
this in a and then we add B plus 2 so a
equals 5 because we set B to 3 and then
we added 2 to B so we're gonna go into
Xcode and just write a few lines of code
just to get a good grasp of this okay
back in Xcode you use delete all that we
previously typed and then declare int a
and then int B now set a equal to B
equals 3 comma and B
plus tip just like what you saw in the
PowerPoint and then NSLog a equals B
equals three comma B plus two equals
percent I a dance in the colon and I
slog
yep at rotations B equals percent I
tation comma B buzz it off a semicolon
and that's all we had to do save it and
build and run now as you can see a
equals B equals three comma B plus two
equals five because you declare be
inside fair play just like I said before
and then you add 2 to 3 that equals five
course and B still equals three so
that's really it for the comment
operator
you