为什么此数组超出索引？ [英] Why is this array out of index?

问题描述

我试图将元素按这种方式构建到二维数组中，但是当代码进入2D数组时，我得到一个错误：数组超出索引。

I am trying to sort elements into a two dimensional array I built this way, but when the code gets to the 2D array I get an error: "array out of index".

var categoryTempArray: [[ProductCatalogue]] = []

func sortinOut(){
    var i = 0
    var j = 0
        for x in categories{
            for y in array{
                if x == String(stringInterpolationSegment: y.categoryName){
                categoryTempArray[i].append(y)
                //categoryTempArray[i][j] = y tried this too
                    j++
                }
            }
            i++
        }}

推荐答案

您应该先初始化第[i]个元素，然后再附加一些[j]

You should initialize the [i]th element before than appending some [j]th element to it.

您将在不存在的项目上调用append（）函数，因为categoryTempArray数组中不存在任何项目，因此索引的边界。

You would call the append() function on an item that does not exist, since no item exists in the categoryTempArray array, thus the index out of bound.

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