VBA字典对象操作技巧

VBA 中集合的功能比较弱，常见的有数组 (array) 、集合 (Collection）和字典，其中字典是 Key-Value Pair 类型的数据结构，适合按 Key 存储和查找。本篇介绍字典的操作方法。

VBA 语法本身并没有字典这种数据结构，需要引用 Microsft Scripting Runtime 库：

Dictionary 本身的方法不多，只有六个：

From: Dictionary 对象 | Microsoft Docs

创建字典对象并添加值

我们使用前期绑定的方式，new Dictionary() 创建字典对象，Add() 方法添加元素

Public Sub CreateDictionary()
    Dim d As New Dictionary
    d.Add "a", "Athens"
    d.Add "b", "Belgrade"
    d.Add "c", "Cairo"    
End Sub

遍历字典

1. 通过 Keys 属性遍历

Public Sub IterateThruKeys()
    Dim d As New Dictionary
    d.Add "a", "Athens"
    d.Add "b", "Belgrade"
    d.Add "c", "Cairo"
    
    Dim k As Variant ' 只能为variant或者object类型
    For Each k In d.Keys
        Debug.Print k, d(k)
    Next
End Sub

VBA 表示集合的元素用的也是圆括号，不像其它语言一般用方括号。

2. 遍历值

Public Sub IterateThruItems()
    Dim d As New Dictionary
    d.Add "a", "Athens"
    d.Add "b", "Belgrade"
    d.Add "c", "Cairo"
    
    Dim v As Variant
    For Each v In d.Items
        Debug.Print v
    Next
End Sub

3. 通过 Count 遍历

Public Sub IterateThruCount()
    Dim d As New Dictionary
    d.Add "a", "Athens"
    d.Add "b", "Belgrade"
    d.Add "c", "Cairo"
    
    Dim i As Integer
    For i = 0 To d.Count - 1
        Debug.Print d.Keys(i), d.Items(i)
    Next
End Sub

下面通过一些小例子加深大家的理解，掌握一些重要的编码方法。

判断 key 是否存在

Public Sub CheckIfExists()
    Dim d As New Dictionary
    Dim i As Integer

    d.Add "a", "Athens"
    d.Add "b", "Belgrade"
    d.Add "c", "Cairo"
    
    If d.Exists("a") Then Debug.Print d("a")
End Sub

将字典的key和value写入工作表

Public Sub WriteToSheet()
    Dim d As New Dictionary
    d.Add "a", "Athens"
    d.Add "b", "Belgrade"
    d.Add "c", "Cairo"
    
    Sheet1.Cells(1, 1).Resize(1, d.Count) = d.Keys
    Sheet1.Cells(2, 1).Resize(1, d.Count) = d.Items
End Sub

执行代码后，字典的值被写入到 Sheet1，界面如下：

image

竖向表达感觉会更直观，下面的代码实现列示呈现：

Public Sub WriteToSheet2()
    Dim d As New Dictionary
    d.Add "a", "Athens"
    d.Add "b", "Belgrade"
    d.Add "c", "Cairo"
    
    Dim i As Integer
    For i = 0 To d.Count - 1
        Sheet1.Range("A1").Offset(i, 0) = d.Keys(i)
        Sheet1.Range("A1").Offset(i, 1) = d.Items(i)
    Next
End Sub

效果：

将 Sheet 中的值转换为字典

如果已经有了如上图在 Excel 工作表的值，下面的代码则将这些值转换为字典：

Public Sub ConvertSheetValueToDict()
    Dim d As New Dictionary
    Dim i As Integer
    Dim startCell As Range
    Set startCell = Sheet1.Range("A1")
    For i = 0 To startCell.CurrentRegion.Rows.Count
        d.Add startCell.Offset(i, 0).Value, startCell.Offset(i, 1).Value
    Next
    
    Dim k As Variant
    For Each k In d.Keys
        Debug.Print k, d(k)
    Next
End Sub

下面给出两个利用字典进行计算的示例。

利用字典进行求和计算

假设我们有如下的左边数据，要实现按品种进行统计：

Public Sub CalculateUsingDict()
    Dim d As New Dictionary
    Dim tbl As Range
    Dim dataRange As Range
    
    ' 不包括表头
    Set tbl = Sheet2.Range("A1").CurrentRegion
    Set dataRange = tbl.CurrentRegion.Offset(1, 0)
        
    Dim row As Range
    Dim cell As Range
    Dim key As String
    For Each row In dataRange.Rows
        key = CStr(row.Cells(1))
        If Not d.Exists(key) Then
            d.Add key, row.Cells(2)
        Else
            d(key) = d(key) + row.Cells(2)
        End If
    Next
    
    Dim k As Variant
    Dim i As Integer
    For i = 0 To d.Count - 1
        Sheet2.Range("H2").Offset(i, 0) = d.Keys(i)
        Sheet2.Range("H2").Offset(i, 1) = d.Items(i)
    Next
End Sub

这里用到了一个小技巧，因为数据包含表头，所以通过变量 dataRange 只包含数据部分，不包括表头。

通过字典进行匹配

假设有如下图左边的数据，需要实现按姓名查找学生三门课的考试成绩，类似 vlookup。

Public Sub MatchUsingDict()
    Dim d As New Dictionary
    Dim tbl As Range
    Dim dataRange As Range
    
    Set tbl = Sheet3.Range("A1").CurrentRegion
    Set dataRange = tbl.CurrentRegion.Offset(1, 0)
        
    Dim row As Range
    Dim cell As Range
    Dim k As String
    Dim v As Variant
    For Each row In dataRange.Rows
        k = CStr(row.Cells(1))
        v = Array(row.Cells(2), row.Cells(3), row.Cells(4))
        d.Add k, v
    Next
    
    Dim key As String
    key = CStr(Sheet3.Range("H2"))
    If d.Exists(key) Then
        Sheet3.Range("H2").Offset(0, 1) = d(key)(0)
        Sheet3.Range("H2").Offset(0, 2) = d(key)(1)
        Sheet3.Range("H2").Offset(0, 3) = d(key)(2)
    End If
End Sub

有兴趣的小伙伴，甚至可以利用 dictionary 编写类似 vlookup 的函数，自己琢磨吧。