类模块——接口排序

能用好类与接口的话，代码的复用率会非常高，是个值得好好学习的东西。

用排序功能来举例，排序是经常使用到的，比如冒泡排序:

Sub BubbleSort(l())
    Dim i As Long, j As Long

    For i = 1 To UBound(l)
        For j = i + 1 To UBound(l)
            If l(i) > l(j) Then
                Call Swap(l, i, j)
            End If
        Next j
    Next i
End Sub

Function Swap(l(), Low As Long, High As Long)
    Dim iTemp
    iTemp = l(Low)
    l(Low) = l(High)
    l(High) = iTemp
End Function

有了这个函数，只要传入1个一维数组，函数执行完后数组就有序了。但是，如果需要排序的是个二维数组的话，就不得不把排序函数重新写过一次，如果是结构体，又得重新写过…… 接口的使用，就可以最小化的来修改这些东西。对于这个排序函数，不管传入的是什么数据，排序算法是固定的，不同的地方是：

2个数据的比较（If l(i) > l(j) Then）
2个数据的交换（ Swap）

排序算法是固定的，要修改的是这2个功能，只要传入的东西里面具有这2个功能就可以了，具有功能的东西，也就是类，类能有自己的方法。但是又不能传入某种具体的类，因为数据的不同，这2个方法也是不相同的，这就需要接口了。接口ISort定义2个功能：

Function Swap(i As Long, j As Long)

End Function

Function Less(i As Long, j As Long) As Boolean

End Function

然后排序函数传入的是这个接口：

Sub BubbleSort(I_Sort As ISort, Low As Long, High As Long)
    Dim i As Long, j As Long

    For i = Low To High
        For j = i + 1 To High
            If I_Sort.Less(j, i) Then
                I_Sort.Swap i, j
            End If
        Next j
    Next i
End Sub

一维数据的实现：

Implements ISort

Private arr() As Variant

Property Let Data(Value As Variant)
    arr = Value
End Property
Property Get Data() As Variant
    Data = arr
End Property

'比较
Private Function ISort_Less(i As Long, j As Long) As Boolean
    ISort_Less = arr(i) < arr(j)
End Function

'交换
Private Function ISort_Swap(i As Long, j As Long) As Variant
    Dim tmp As Variant

    tmp = arr(i)
    arr(i) = arr(j)
    arr(j) = tmp
End Function

二维数组实现接口：

Implements ISort

Private Type LowHigh
    Low As Long
    High As Long
End Type

Private arr() As Variant
Private i_col As Long           '要排序的列
Private Col_Bound As LowHigh    '列的上下标

Property Let SortCol(iCol As Long)
    i_col = iCol
End Property

Property Let Data(Value As Variant)
    arr = Value
    
    Col_Bound.Low = LBound(arr, 2)
    Col_Bound.High = UBound(arr, 2)
End Property
Property Get Data() As Variant
    Data = arr
End Property

'比较
Private Function ISort_Less(i As Long, j As Long) As Boolean
    ISort_Less = arr(i, i_col) < arr(j, i_col)
End Function

'交换
Private Function ISort_Swap(i As Long, j As Long) As Variant
    Dim tmp As Variant
    Dim k As Long
    
    For k = Col_Bound.Low To Col_Bound.High
        tmp = arr(i, k)
        arr(i, k) = arr(j, k)
        arr(j, k) = tmp
    Next k
End Function