Iterating through array to find occurrences of value - arrays

Question

I have been trying to iterate through an array to check how many times two particular values occur. I came up with this code:
var paymentNum = 0
var creditNum = 0
for index in images {
if images.objectAtIndex(index) == 0 {
paymentNum = paymentNum + 1
} else {
creditNum = creditNum + 1
}
}
This doesn't seem to work though. I just get the error 'AnyObject' is not convertible to 'Int'.
Where am I going wrong?

Answer 1

I'm making some pretty huge assumptions because you don't have much detail about what's going on.
I'm assuming that images is an NSArray. NSArray in Objective-C translates into an [AnyObject] in swift.
When you have a for-each style loop like this
for value in array
{}
the loop will iterate through each value in the array. Value is the actual object in the array, not a counter as in a for(int i = 0; i < 10; i++) style loop
So what you're probably really expecting to do is
for item in images {
if item == 0 {
paymentNum++
} else {
creditNum++
}
}
you also might need to cast the loop from an [AnyObject] to an [Int] like this
let tmp = images as [Int]
for item in tmp
{...}
or, cast the value pulled out of the array like this
for item in images {
if (item as Int) == 0 {
paymentNum++
} else {
creditNum++
}
}
But the former is probably preferable

Answer 2

paste ina playground:
import Foundation
let images = [1, 0, 1, 1, 0, 0, 1, 0, 1, 1]
var paymentNum = 0
var creditNum = 0
for item in images {
println(item)
if item == 0 {
paymentNum = paymentNum + 1
} else {
creditNum = creditNum + 1
}
}
println(paymentNum) //4
println(creditNum) //6

Answer 3

There's a more compact way of achieving that, in just 2 lines of code.
It makes the assumption that an array element it's a credit if its value is 1, otherwise is 0.
That said, if you sum up all elements of array, you obtain the number of credits - the number of payments is the array size minus the number of credits.
To sum all elements of the array, the simplest way is using the reduce method (more info here)
var creditNum = images.reduce(0, combine: { $0 + $1 } )
var paymentNum = images.count - creditNum
If using values different than 0 or 1 to identify credits and payments, then the calculation can be modified to check for explicit values as follows:
var creditNum = images.reduce(0, combine: { $0 + ($1 == 1 ? 1 : 0) } )
Here it takes the previous count ($0) and add either 1 or 0, depending whether the element array ($1) is equal to 1 or not.