致命錯誤：索引超出范圍？ 但它是嗎？

Question

我有一個非常奇怪的數組，我不確定我錯過了什么，我確定一些非常簡單的東西。 這是我的代碼，此代碼循環一個包含對象和變量數組的結構，並嘗試找到類別 = 1 的對象，當為真時，它將對象數組發送到另一個數組中。 一切正常，直到我嘗試將數組復制到已排序的數組中，代碼中有更多注釋。 當用戶單擊某個類別時，我試圖對 tableView 進行排序，4 個可能的類別是 1,30,31,32（不要問為什么）

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

無需深入研究代碼的結構以及如何以更“Swifty”的方式編寫代碼，我可以看到問題在於這不是在 Swift 中附加到數組的好方法。

            let currentNoSortedCourses = sortedCourses.count
            sortedCourses[currentNoSortedCourses] = courses[count]

這是訪問越界並導致崩潰的索引。 要在 Swift 中附加到數組，請使用append方法。

        sortedCourses.append(courses[count])

雖然我在這里，但我不妨告訴您，解決您的問題的更好方法（一個班輪）可能是這樣的

    sortedCourses = courses.filter { $0.categories.contains(1) }