【VBA】指定の文字列が含まれているか & 前後の文字列を返す｜InStr/InStrRev

' Minimal, intent-revealing string utilities (contains/left-of/right-of)
' 含有判定・前方抽出・後方抽出に特化した最小ユーティリティ

Option Explicit

Public Enum FindOrigin
	FromStart = 0	' search from the beginning｜前から探す
	FromEnd = 1		' search from the end｜後ろから探す
End Enum

' ContainsText: check if keyword exists in targetString (case-insensitive by default)
' ContainsText: 指定語が含まれるか（既定は大文字小文字を無視）
Public Function ContainsText( _
                            		ByVal targetString As String, _
                            		ByVal keyword As String, _
                            		Optional ByVal compare As VbCompareMethod = vbTextCompare) As Boolean
	ContainsText = (InStr(1, targetString, keyword, compare) > 0)
End Function

' slice the part before marker (choose first/last occurrence)
' 区切り語の手前を返す（最初/最後を選択可能）
Public Function LeftOf( _
                              		ByVal targetString As String, _
                            		ByVal keyword As String, _
                               		Optional ByVal origin As FindOrigin = FromStart, _
                            		Optional ByVal compare As VbCompareMethod = vbTextCompare) As String
	Dim p As Long
	If origin = FromEnd Then
		p = InStrRev(targetString, keyword, -1, compare)
	Else
		p = InStr(1, targetString, keyword, compare)
	End If
	If p > 0 Then
		LeftOf = Left$(targetString, p - 1)
	End If
End Function

' slice the part after marker (choose first/last occurrence)
' 区切り語の後ろを返す（最初/最後を選択可能）
Public Function RightOf( _
                            		ByVal targetString As String, _
                            		ByVal keyword As String, _
                            		Optional ByVal origin As FindOrigin = FromEnd, _
                            		Optional ByVal compare As VbCompareMethod = vbTextCompare) As String
	Dim p As Long
	If origin = FromEnd Then
		p = InStrRev(targetString, keyword, -1, compare)
	Else
		p = InStr(1, targetString, keyword, compare)
	End If
	If p > 0 Then
		RightOf = Mid$(targetString, p + Len(keyword)) ' multi-char safe｜複数文字でも安全
	End If
End Function

Debug.Print LeftOf("りんごは赤い", "赤")   ' → "りんごは"
Debug.Print RightOf("りんごは赤い", "赤")  ' → "い"

Dim source As String
Dim keyword As String

source = "りんごは赤い"
keyword = "赤"

If InStr(source, keyword) > 0 Then
    ' keywordが見つかったときの処理
End If