Fatal error: Index Out of range? BUT IS IT? - arrays

Question

I have a very weird array and I am not sure what I am missing, something very simple I am sure. Here is my code, This code loops a struct with arrays of objects and variables and attempts to find the objects which category = 1, when this is true, it sends the array of objects into another array. Everything works fine, until I try to copy the array into the sorted array, more comments in code. I am trying to sort a tableView when the user clicks a certain category, the 4 possible categories are 1,30,31,32 (don't ask why)
var courses = [Course]()
var sortedCourses = [Course]()
#objc func catOthersButtonObj(_ sender: UIButton){ //<- needs `#objc`
var count = 0
let courseCount = courses.count
let otherCat = 1
// set count to loop the number of detected arrays
// this category looks for the number 1
print("courseCount = " + String(courseCount)) // to debug if courseCount is accurate, it is
//let noOfCat = courses.categories.count
while (count < courseCount)
{
print("count = " + String(count)) // to debug if count is increasing every loop, it is
let totalNoCat = (courses[count].categories?.count)!
var catCount = 0
// while entering a loop of arrays of objects, it searches for the array "categories" and sets totalNoCat = number of categories, this is neccesary because one object can have many categories
// catCount is used to loop through the number of detect categories
if (totalNoCat == 0)
{
break
}
// If no categories is detected, next array
while (catCount < totalNoCat)
{
print("totalNoCat = " + String(totalNoCat))
print("catCount = " + String(catCount))
// debug, check if totalNoCat is detected
// debug, catCount if number of categories is detected and added
if (courses[count].categories?[catCount] == otherCat)
{
print("category Detected = " + String((courses[count].categories?[catCount])!))
// see if category is 1, when it is 1, this is triggered, so its working fine
let currentNoSortedCourses = sortedCourses.count
print("currentNoSortedCourses = " + String(currentNoSortedCourses))
// check the number of sorted array, this is to add array into the next array
// if there is 0 number of sorted arrays, then sorted[0] should be course[detectarray category = 0 array]
//print(courses[count]) checks if courses[count] has data, it does
sortedCourses[currentNoSortedCourses] = courses[count] //where the error is
//here it is sortedCourses[0] = courses[7] ( 7 is which the array detected the correct category
break
}
catCount = catCount + 1
print("Category Detected = " + String((courses[count].categories?[catCount - 1])!))
//debug, if category not 1, show what it is
}
count = count + 1
}
}
Print results
courseCount = 50
count = 0
totalNoCat = 2
catCount = 0
Category Detected = 31
totalNoCat = 2
catCount = 1
Category Detected = 30
count = 1
totalNoCat = 2
catCount = 0
Category Detected = 31
totalNoCat = 2
catCount = 1
Category Detected = 30
count = 2
totalNoCat = 1
catCount = 0
Category Detected = 30
count = 3
totalNoCat = 2
catCount = 0
Category Detected = 32
totalNoCat = 2
catCount = 1
Category Detected = 30
count = 4
totalNoCat = 2
catCount = 0
Category Detected = 32
totalNoCat = 2
catCount = 1
Category Detected = 30
count = 5
totalNoCat = 1
catCount = 0
Category Detected = 32
count = 6
totalNoCat = 2
catCount = 0
Category Detected = 32
totalNoCat = 2
catCount = 1
Category Detected = 30
count = 7
totalNoCat = 1
catCount = 0
category Detected = 1
currentNoSortedCourses = 0

Answer 1

Without going much into the structure of the code and how it can be written in a more "Swifty" way, I can see the problem is that this is not a good way to append to an array in Swift.
let currentNoSortedCourses = sortedCourses.count
sortedCourses[currentNoSortedCourses] = courses[count]
This is accessing an index that is out of bounds and causes a crash. To append to an array in Swift use append method.
sortedCourses.append(courses[count])
Whilst I'm here I might as well tell you that a better way (one liner) to solve your problem probably be something like this
sortedCourses = courses.filter { $0.categories.contains(1) }