iphone: how to check uitableview row modulus - iphone

Question

it's a hard to explain issue so i hope i can state it
i have a tableview and i want that..
row number 1 have a background and row number 2 have another background .
and row number 3 have a third background..
the fourth row should have the first background and the fifth should have the second ..
and so forth ..
i used this code
if(row+1%1==0){
bg = [UIImage imageNamed:#"row1.png"];
selectionBg = [UIImage imageNamed:#"row1.png"];
}
else if(row+1%2==0){
bg = [UIImage imageNamed:#"row2.png"];
selectionBg = [UIImage imageNamed:#"row2.png"];
}else if(row+1%3==0){
bg = [UIImage imageNamed:#"row3.png"];
selectionBg = [UIImage imageNamed:#"row3.png"];
}
i'm trying to use modulus but i get lost .. so is there a way for that?
thanks in advance

Answer 1

You should use mod 3 because you have three options:
if (row % 3 == 0) {
// Option A
} else if (row % 3 == 1) {
// Option B
} else {
// Option C
}
By the way, do you understand what a modulo operation does? This might be interesting to read (from Wikipedia):
In computing, the modulo operation finds the remainder of division of
one number by another.
Given two positive numbers, a (the dividend)
and n (the divisor), a modulo n (abbreviated as a mod n) can be
thought of as the remainder, on division of a by n. For instance, the
expression "5 mod 4" would evaluate to 1 because 5 divided by 4 leaves
a remainder of 1, while "9 mod 3" would evaluate to 0 because the
division of 9 by 3 leaves a remainder of 0; there is nothing to
subtract from 9 after multiplying 3 times 3.
This is what happens in the code:
row row % 3 option
0 0 A
1 1 B
2 2 C
3 0 A
4 1 B
5 2 C
6 0 A
… … …

Answer 2

Instead of using the modulos use a static counter
Like the following
static int rowBGSelector = 0;
switch (rowBGSelector) {
case 0:
NSLog(#"%d, first", i); //Chose BG 1
break;
case 1:
NSLog(#"%d, second", i); //Chose BG 2
break;
case 2:
NSLog(#"%d, third", i); //Chose BG 3
break;
default:
rowBGSelector = -1; //Reset the static
break;
}
rowBGSelector++; //Increment