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Switch statement and strings
Switch statement and strings

Description

This article describes how to translate an AnsiString variable into an integer so that it can be used in a switch statement. Two methods are introduced: the function method and the map method. The project includes a form with two TButtons buttons: Button1 and Button2.

Switch.cpp

#include <vcl.h>
#pragma hdrstop

#include "Switch.h"
#include <map>
//----------------------------------------------------------------------
#pragma package(smart_init)
#pragma resource "*.dfm"
TForm1 *Form1;
//----------------------------------------------------------------------
__fastcall TForm1::TForm1(TComponent* Owner)
        : TForm(Owner)
{
}
//----------------------------------------------------------------------

int SwitchVariable( String S )
{
//Function method
    String Values[] = {"value0", "value1", "value2", "value3", "value4",
                       "value5", "value6", "value7", "value8", "value9" };

    for ( int i=0; i< ARRAYSIZE( Values ); i++ )
       if ( S == Values[i] )
           return i;
    return -1;   //Error: Illegal input
}
//---------------------------------------------------------------

void __fastcall TForm1::Button1Click(TObject *Sender)
{
//Function method

    switch ( SwitchVariable( "value8" )  )
    {
        case 0:
             ShowMessage( "0" );
             break;
        case 1:
             ShowMessage( "1" );
             break;
        case 2:
             ShowMessage( "2" );
             break;
        case 3:
             ShowMessage( "3" );
             break;
        case 4:
             ShowMessage( "4" );
             break;
        case 5:
             ShowMessage( "5" );
             break;
        case 6:
             ShowMessage( "6" );
             break;
        case 7:
             ShowMessage( "7" );
             break;
        case 8:
             ShowMessage( "8" );
             break;
        case 9:
             ShowMessage( "9" );
             break;

        default: ShowMessage( "Illegal string value" );
    }
}
//-----------------------------------------------------------------

void __fastcall TForm1::Button2Click(TObject *Sender)
{
//Map Method:

    std::map MapValues;

    MapValues["value1" ] =  1;
    MapValues["value2" ] =  2;
    MapValues["value3" ] =  3;
    MapValues["value4" ] =  4;
    MapValues["value5" ] =  5;
    MapValues["value6" ] =  6;
    MapValues["value7" ] =  7;
    MapValues["value8" ] =  8;
    MapValues["value9" ] =  9;
    MapValues["value10"] = 10;

    switch( MapValues["value5"] )
    {
            case 1:
                ShowMessage( "1" );
                break;
            case 2:
                ShowMessage( "2" );
                break;
            case 3:
                ShowMessage( "3" );
                break;
            case 4:
                ShowMessage( "4" );
                break;
            case 5:
                ShowMessage( "5" );
                break;
            case 6:
                ShowMessage( "6" );
                break;
            case 7:
                ShowMessage( "7" );
                break;
            case 8:
                ShowMessage( "8" );
                break;
            case 9:
                ShowMessage( "9" );
                break;
            case 10:
                ShowMessage( "10" );
                break;

            default: ShowMessage("Illegal String Value");
    }
}

Switch.h

#ifndef SwitchH
#define SwitchH
//---------------------------------------------------------------------------
#include <Classes.hpp>
#include <Controls.hpp>
#include <StdCtrls.hpp>
#include <Forms.hpp>
//---------------------------------------------------------------------------
class TForm1 : public TForm
{
__published:	// IDE-managed Components
        TButton *Button1;
        TButton *Button2;
        void __fastcall Button2Click(TObject *Sender);
        void __fastcall Button1Click(TObject *Sender);
private:	// User declarations
public:		// User declarations
        __fastcall TForm1(TComponent* Owner);
};
//---------------------------------------------------------------------------
extern PACKAGE TForm1 *Form1;
//---------------------------------------------------------------------------
#endif

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