Objective-C Tutorial - Lesson 30: While Loops Video Lecture | Learn and Understand: Objective C (English) - Web Development

what's up guys join here are the
objective-c toros less than 30 while
loops and as we remember last lesson we
went over the for loop which is used
when you know how many times you'll have
to go through the loop now while and
do-while loops which we'll go over next
lesson repeat until condition is met so
basically for the most part you can look
at the top of a for loop and figure out
the number of iterations for it whereas
with while loops they're mainly use when
you don't know exactly how many times
the loop will repeat so here is the
generic set up for a while loop you have
Wow which tells the compiler that this
is a while loop then you have the
condition which is evaluated and if that
condition is true the statements are run
if it's false the statements right after
the loop are executed in the program
continues now let's say the condition
was true so the statements to execute or
run and then the loop goes back to step
one and the loop runs until the
condition is false now some details
about wild loops now the loop may
actually never be run because the
condition is usually contingent on
outside conditions so let's say we have
this loop that runs only if the user
enters information into the England
transaction budget now if the user only
entered information into the Europe
transaction budget this loop wouldn't
run because one of the conditions was
for the user to do something to enter
information into the England transaction
budget that users didn't do that so the
condition is false so that's a good
example of how as you're typing up this
loop you really have no control over
whether it's going to run or not and
also just remember that the value of the
condition has to change in order for the
loop to end that's something very basic
with loops but just remember that
because you in most cases you probably
won't have control over whether or not
that's going to change right within
close range of that loop it may be
someplace way off in your program just
kind of you'll just have to know what
all is going on
in your program and while loops act very
similar to for loops in the generic
example but usually you will be testing
an outside condition and a good example
is updating the position of an object
and amazed as the user moves his iOS
device in this example you wouldn't know
how many times the loop will need to
repeat now you can use a while loop as a
for loop how you would do this is you
first have to declare some value so in
our case int N equals 1 then you set up
the while loop you have the condition n
is less than 3 and then you have to
increment it at the end of that loop so
just remember you have to declare the
variable outside loop in the ink in the
increase or at the end of the statements
and notice that while loops simply
accept a condition so there's no spot
for a counter or an incrementer it's
just one spot for condition so all in
all the basic difference between a for
loop and a while loop for loop you know
how many times the loop will run while
loop it's more iffy on whether the loop
will run or not and it runs until the
condition which remember is based on an
outside condition is false so now we're
going to jump into Xcode and code up a
while loop okay so here we are in Xcode
and there really isn't a lot for us to
do this time all we're going to be doing
is just adding a while loop around this
transaction right here and we are going
to be creating this while loop in such a
way that it's very similar to the for
loop right up here because what we're
going to be doing is we're going to
actually declare a little variable and
then assign a value to it and that's
what the condition is going to be in the
while loop so it's not exactly how we
would necessarily use a while loop in a
regular to this traditional program but
nonetheless we're still working with the
mechanics of the while loop and we're so
understanding how it runs and works so
that's the important part so while the
condition and
less than three then the brace okay um
we have to make those few modifications
so change this to a transaction just
like last time then a transaction and
then let's make this one same as above
so it's n times 100 so it will change by
100 increments each time and the type is
charged this time and then add object a
transaction then remember at the bottom
and plus plus and that's all that we're
going to be adding for this lesson so we
can go ahead and build and run say ball
so the first two lines are the exact
same thing as last time then the next
line charging one hundred dollars in
foreign currency leaves 575 just what we
expected then charging two hundred
dollars notice the increase by one
hundred dollars in foreign currency
leaves 325 so everything built and ran
just like we expected just remember that
a while would only has a spot for a
condition in that condition is
contingent on an outside condition in
this case the outside condition was int
N equals one so even though we set this
while loop up very much like a a for
loop it still runs the same basic way as
any other while loop would aside from
the part that we had the incrementer at
the end of our loop typically this value
would be changing somewhere else in the
program but how we set up this while
loop is completely fine we still
understand all the mechanics and basics
of a while loop and so a lot easier to
work with but thanks for checking out
this video be sure to subscribe up above
to be notified when I upload less than
thirty one where we'll be going over the
do-while loop and we'll just be adding
another transaction here and then adding
the do-while loop around it so be sure
to subscribe to be notified about that
and comment any suggestions or questions
down below be sure to LIKE this video if
it helps you out and I'll see you in the
next one real soon thanks for watching
you