Objective-C Tutorial - Lesson 31: Do While Loops Video Lecture | Learn and Understand: Objective C (English) - Web Development

what's up guys join here of the
objective-c Toros lesson 31 do-while
loops and as you remember last lesson we
went over while loops so you may be
saying well what's the difference
between a while and do-while loop well
they're the same thing except for one
thing
with a do-while loop the condition is
evaluated after the loop so this means a
do-while loop will always run at least
once and down there at the bottom you
can see the generic example of a
do-while loop so how I do while loop
works do tells the compiler that this is
a do-while loop then statements to do
while the condition is true or run at
least once
then while condition is evaluated if
true the loop goes back to step one if
false the program continued it continues
on now steps 2 through 3 are run until
the condition is false then the program
continues now a little bit more
information about the do-while loop if
there is a chance you do not want your
loop to run and do not do not use a
do-while loop an example is if there was
the possibility of an array being empty
you would not want to use a do-while
loop to iterate through it and do-while
loops are ended with a semicolon just to
remember that as you can see in the
example there and however other loops
are not terminated with a semicolon so
just remember that the do-while loop is
the only loop that is ended with a
semicolon not a brace and that's all for
this lesson there wasn't too much to go
over so now we're going to jump into
Xcode and add a do-while loop to our
code ok so here we are in Xcode and
we're just going to add the do-while
loop right below the other two loops so
say du then we're just going to put in
all this information that we put in and
the other two loops so a transaction
just gonna finish declaring this object
transaction new then a transaction
called the create transaction method
we're going to do the same n times 100
and I've type we're gonna make this
charge then we're gonna add it to the
transactions right so add objects a
transaction close that all out then we
need to increment N and whoops semicolon
then close that loop out or a number
that then we still have to put a while
and then the condition n is less than or
equals to 3 then closed out with the
semicolon and then we're all done so we
go ahead and build and run save all so
the first four lines here are what we
worked with the last two lessons go to
the fifth line where you see charging
$300 in foreign currency leaves negative
$50 that's exactly what we expected
because 300 times that transaction rate
of 1.25 is 375 subtracted from 30 25 is
negative $50 so just what we expected
would happen happened and but you may be
saying well why is it $300 well to
understand that you first have to look
at this while loop so N equals 1 so 1 is
less than 3 that's correct it goes
through then increments so now N equals
2 so 2 is less than 3 that's correct so
it runs through again so that's why it
ran through twice then it's incrementing
again so 3 is less than 3 no that's not
true
so it jumps down here and runs through
this do-while loop so it runs through
this one time it increments n to 4 and
then checks the condition while n is
less than or equal to 3 so 4 is less
than or equal to 3 that's not correct
so then it ends the loop and it only ran
that one time the the default time that
a do-while loop will always run so
that's all for loops we're all done
talking about them now so that's the for
loop while loop do-while loop and then
we have the for in loop
right there so four types of loops that
you now know a lot about so that's all
for this lesson be sure to leave any
comments or questions or suggestions
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this video helped you out and I'll see
you in my next video real soon later