Crearea meniurilor unei aplicatii [C, Text Based]

Foarte multe probleme scolaresti, si nu numai, cer la un moment dat crearea unui meniu care prezinta utilizatorului mai multe optiuni, utilizatorul urmand sa aleaga una din ele.

Astfel, un cod tipic ajunge sa arate cam asa:

#include <stdio.h>
#include <stdlib.h>

int main(void)
{
	int value = 0;
	int choice = 0;

	while (choice != 3)
	{
		printf("1. Aduna o unitate\r\n");
		printf("2. Scade o unitate\r\n");
		printf("3. Iesire\r\n");
		scanf("%d", &choice);

		switch (choice)
		{
		case 1:
			value += 1;
			printf("Dupa adunare, value = %d\r\n", value);
			break;
		case 2:
			value -= 1;
			printf("Dupa scadere, value = %d\r\n", value);
			break;
		}
	}

	return 0;
}

Chiar daca inca nu arata asa rau, daca sunt multe optiuni, treaba se complica:

• Dezvoltatorul trebuie sa fie atent ce indice introduce pentru fiecare optiune pentru a nu le incurca
  
• Cand apare o noua optiune, trebuie deobicei decalate altele
  
• A scrie mult cod intr-un switch nu e recomandat
  
• Multi uita, la un moment dat, sa introduca break peste tot

Asadar, cum se poate imbunatatii? Folosind functii si pointeri

Definim un tip de pointer la functii

typedef void(*optionCallback)(void* data);

Fiecare optiune va avea asociata o functie. Acea functie va fi apelata cand utilizatorul alege optiunea in cauza. Pentru a nu folosi variabile globale, functia va primi drept parametru un pointer la orice.

Definim o structura de date pentru a pastra toate optiunile

typedef struct
{
	const char* displayText;
	optionCallback callback;
	int triggersExit;
} option;

Definim un vector de optiuni
Fiecare optiune va avea un nume, o functie ce va fi apelata, si un parametru care indica daca loop-ul va fi intrerupt sau nu.

option options[] =
{
	{ "Aduna o unitate", addUnit, 0 },
	{ "Scade o unitate", subtractUnit, 0 },
	{ "Iesire", NULL, 1 }
};

Apelam o functie ce se ocupa de afisarea efectiva a meniului

displayMenu(options, sizeof(options) / sizeof(options[0]), &value);

Pare complicat?
Este usor mai complicat, dar:

• Definesc intr-un loc toate optiunile
  
• Nu mai trebuie sa fiu atent la ordinea lor
  
• Am separat codul ce trateaza fiecare optiune
  
• Pot crea oricand o functie de afisare mai buna

Codul complet:

#include <stdio.h>
#include <stdlib.h>

typedef void(*optionCallback)(void* data);

typedef struct
{
	const char* displayText;
	optionCallback callback;
	int triggersExit;
} option;

void displayMenu(const option options[], size_t nrOptions, void* data)
{
	size_t i = 0;
	size_t choice = 0;
	int exit = 0;

	while ( ! exit)
	{
		for (i = 0; i < nrOptions; i++)
		{
			printf("%d. %s\r\n", i + 1, options[i].displayText);
		}
		scanf("%u", &choice);
		choice -= 1;
		if (choice >= nrOptions)
		{
			printf("Alegere gresita\r\n");
		}
		else
		{
			if (options[choice].callback)
			{
				options[choice].callback(data);
			}
			exit = options[choice].triggersExit;
		}
	}
}

void addUnit(void* data)
{
	int* value = (int*)data;
	*value += 1;
	printf("Dupa adunare, value = %d\r\n", *value);
}

void subtractUnit(void* data)
{
	int* value = (int*)data;
	*value -= 1;
	printf("Dupa scadere, value = %d\r\n", *value);
}

int main(void)
{
	int value = 0;

	option options[] =
	{
		{ "Aduna o unitate", addUnit, 0 },
		{ "Scade o unitate", subtractUnit, 0 },
		{ "Iesire", NULL, 1 }
	};

	displayMenu(options, sizeof(options) / sizeof(options[0]), &value);

	return 0;
}

Avand un sistem mai flexibil, putem crea o functie ce prezinta un meniu mai usor de folosit, din sageti.

#include <Windows.h>

void displayNiceMenu(const option options[], size_t nrOptions, void* data)
{
	HANDLE console, consoleInput;
	CONSOLE_SCREEN_BUFFER_INFO screenBuffer;
	INPUT_RECORD record;
	COORD screenCoords;
	int columns, rows;
	DWORD charsWritten, eventsRead;
	char buffer[1024] = {0};
	size_t i = 0, j = 0;
	size_t choice = 0;
	int exit = 0, keyPressed = 0;
	const WORD normalColor = FOREGROUND_RED | FOREGROUND_GREEN | FOREGROUND_BLUE | BACKGROUND_BLUE;
	const WORD selectedColor = BACKGROUND_RED | BACKGROUND_GREEN | BACKGROUND_BLUE | FOREGROUND_BLUE;


	console = GetStdHandle(STD_OUTPUT_HANDLE);
	consoleInput = GetStdHandle(STD_INPUT_HANDLE);
	screenCoords.X = 0;
	screenCoords.Y = 0;

	GetConsoleScreenBufferInfo(console, &screenBuffer);
	columns = screenBuffer.srwindow.Right - screenBuffer.srwindow.Left + 1;
	rows = screenBuffer.srwindow.Bottom - screenBuffer.srwindow.Top + 1;

	SetConsoleTextAttribute(console, normalColor);

	while (!exit)
	{
		//clear screen
		FillConsoleOutputCharacterA(console, ' ', rows*columns, screenCoords, &charsWritten);

		//set cursor to beginning of screen
		SetConsoleCursorPosition(console, screenCoords);

		ZeroMemory(buffer, sizeof(buffer));
		for (i = 0; i < columns; i++)
		{
			buffer[i] = 205;
		}
		buffer[0] = 201;
		buffer[columns - 1] = 187;
		WriteConsoleA(console, buffer, strlen(buffer), &charsWritten, NULL);

		for (i = 0; i < nrOptions; i++)
		{
			ZeroMemory(buffer, sizeof(buffer));
			buffer[0] = 186;
			buffer[1] = ' ';
			WriteConsoleA(console, buffer, strlen(buffer), &charsWritten, NULL);

			if (choice == i)
			{
				SetConsoleTextAttribute(console, selectedColor);
			}

			ZeroMemory(buffer, sizeof(buffer));
			strcpy(buffer, options[i].displayText);
			for (j = strlen(buffer); j < (columns - 3); j++)
			{
				buffer[j] = ' ';
			}
			WriteConsoleA(console, buffer, strlen(buffer), &charsWritten, NULL);

			if (choice == i)
			{
				SetConsoleTextAttribute(console, normalColor);
			}

			ZeroMemory(buffer, sizeof(buffer));
			buffer[0] = 186;
			WriteConsoleA(console, buffer, strlen(buffer), &charsWritten, NULL);
		}

		ZeroMemory(buffer, sizeof(buffer));
		for (i = 0; i < columns; i++)
		{
			buffer[i] = 205;
		}
		buffer[0] = 200;
		buffer[columns - 1] = 188;
		WriteConsoleA(console, buffer, strlen(buffer), &charsWritten, NULL);

		while ( ! keyPressed)
		{
			ZeroMemory(&record, sizeof(record));
			ReadConsoleInput(consoleInput, &record, 1, &eventsRead);

			if (record.EventType == KEY_EVENT && record.Event.KeyEvent.bKeyDown)
			{
				if (record.Event.KeyEvent.wVirtualKeyCode == 13)
				{
					if (options[choice].callback)
					{
						options[choice].callback(data);
					}
					exit = options[choice].triggersExit;
					break;
				}
				if (record.Event.KeyEvent.wVirtualKeyCode == 40)
				{
					choice = (choice + 1) % nrOptions;
					break;
				}
				else if (record.Event.KeyEvent.wVirtualKeyCode == 38)
				{
					if (choice == 0)
					{
						choice = nrOptions - 1;
					}
					else
					{
						choice = (choice - 1) % nrOptions;
					}
					break;
				}
			}
		}
	}
}

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Edited by dani.user, 25 January 2015 - 23:12.