動作環境

C++ Builder XE4
RAD Studio 10.2 Tokyo Update 2 (追記: 2017/12/28)

仕様

Button押下時、ButtonのTagプロパティ値と同じ値をTagプロパティに持つTMemoのTextを取得する

code v0.1

Unit1.h

//---------------------------------------------------------------------------

# ifndef Unit1H
# define Unit1H
//---------------------------------------------------------------------------
# include <System.Classes.hpp>
# include <Vcl.Controls.hpp>
# include <Vcl.StdCtrls.hpp>
# include <Vcl.Forms.hpp>
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published:	// IDE で管理されるコンポーネント
	TButton *Button1;
	TMemo *Memo1;
	TMemo *Memo2;
	TMemo *Memo3;
	void __fastcall Button1Click(TObject *Sender);
private:	// ユーザー宣言
	String __fastcall getMemoText(TForm *frmPtr, String tag);
public:		// ユーザー宣言
	__fastcall TForm1(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
# endif

Unit1.cpp

//---------------------------------------------------------------------------

# include <vcl.h>
# pragma hdrstop

# include "Unit1.h"
//---------------------------------------------------------------------------
# pragma package(smart_init)
# pragma resource "*.dfm"
TForm1 *Form1;
//---------------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
	: TForm(Owner)
{
}
//---------------------------------------------------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)
{
	if (Sender == NULL) {
		return;
	}

	TComponent *cmpPtr = (TComponent *)Sender;
	String ret = getMemoText(this, cmpPtr->Tag);
	ShowMessage(ret);
}

String __fastcall TForm1::getMemoText(TForm *frmPtr, String tag)
{
	String ret = L"";
	for(int idx=0; idx < frmPtr->ComponentCount; idx++) {
		if (dynamic_cast<TMemo *>(frmPtr->Components[idx]) == NULL) {
			continue;
		}

		TMemo *mmPtr = (TMemo *)frmPtr->Components[idx];
		if (mmPtr->Tag != tag) {
			continue;
		}

		ret = mmPtr->Text;
	}

	return ret;
}
//---------------------------------------------------------------------------

TForm *frmPtrを渡しているのは、別のユニットに持っていく前準備として。同じフォームで使う場合はthisで十分。

設定

Memo1
- Tag: 3141
- Text: Memo3141
Memo2
- Tag: 2718
- Text: Memo2718
Memo3
- Tag: 6022
- Text: Memo6022
Button
- Tag: 2718

結果