Loops can visit each value in a collection and build a result.

Accumulate values

collection_iteration.swift
let bonus = 
let baseScores = [2, 4, 6]
var total = 0

for score in baseScores {
    total = total + score + bonus
}

print("bonus=\(bonus)")
print("total=\(total)")
let bonus = 
let baseScores = [2, 4, 6]
var total = 0

for score in baseScores {
    total = total + score + bonus
}

print("bonus=\(bonus)")
print("total=\(total)")
let bonus = 
let baseScores = [2, 4, 6]
var total = 0

for score in baseScores {
    total = total + score + bonus
}

print("bonus=\(bonus)")
print("total=\(total)")
iteration A `for` loop over an array handles each element in order. The running total shows how repeated updates build a final result.