Факэдэ загвар

Факэдэ (Фасад) загвар нь Програм хангамжийн инженерчлэл сэдэвт хамаарагдах зохиомжийн загвар-уудын нэг бөгөөд ихэвчлэн Объект хандалтат технологи-той цуг ашиглагддаг.

Факэдэ нь обьект бөгөөд class library шиг томоохон кодтой хэсэг рүү хандах замыг хөнгөвчилж өгдөг. Факэдэ загварыг ашигласнаар дараахи давуу талуудтай:

• Факэдэ загварыг ихэнхи кодын ажлуудад ашиглахад тохиромжтой учраас software library-г ашиглах, ойлгох, тест хийхэд хялбар болдог;
• library ашиглаж байгаа кодыг уншихад илүү хялбар болгоно;
• Ихэнхи программын код факэдэ загварыг ашиглачих учраас library доторхи ажлууд ба гадаад код 2-ын хоорондын хамаарал багасна. Ингэснээр системийг илүү уян хатан хөгжүүлэх боломжтой болно.
• муу загварчлагдсан API-нуудын цуглуулгыг зөв зохион байгуулагдсан ганц API болгоно.

Бүтэц

Facade (Загвар:Pron-en)

The facade class abstracts Packages 1, 2, and 3 from the rest of the application.

Clients

The objects using the Facade Pattern to access resources from the Packages.

Packages

Жишээнүүд

Java

This is an abstract example of how a client ("you") interacts with a facade (the "computer") to a complex system (internal computer parts, like CPU and HardDrive).

/* Complex parts */

class CPU {
	public void freeze() { ... }
	public void jump(long position) { ... }
	public void execute() { ... }
}

class Memory {
	public void load(long position, byte[] data) {
		...
	}
}

class HardDrive {
	public byte[] read(long lba, int size) {
		...
	}
}

/* Facade */

class Computer {
	private CPU cpu=null;
	private Memory memory=null;
	private HardDrive hardDrive=null;

	public Computer() {
		this.cpu=new CPU();
		this.memory=new Memory();
		this.hardDrive=new HardDrive();
	}

	public void startComputer() {
		cpu.freeze();
		memory.load(BOOT_ADDRESS, hardDrive.read(BOOT_SECTOR, SECTOR_SIZE));
		cpu.jump(BOOT_ADDRESS);
		cpu.execute();
	}
}

/* Client */

class You {
	public static void main(String[] args) {
		Computer facade = new Computer();
		facade.startComputer();
	}
}

C#

using System;

namespace Facade
{
	public class CPU
        {
		public void Freeze() { }
		public void Jump(long addr) { }
		public void Execute() { }
	}

	public class Memory
	{
		public void Load(long position, byte[] data) { }
        }

	public class HardDrive
	{
		public byte[] Read(long lba, int size) { return null; }
	}

	public class Computer
	{
		CPU _cpu = new CPU();
		Memory _memory = new Memory();
		HardDrive _hardDrive = new HardDrive();

		public void StartComputer()
		{
			_cpu.Freeze();
			_memory.Load(0x22, hardDrive.Read(0x66, 0x99));
			_cpu.Jump(0x44);
			_cpu.Execute();
		}
	}

	public class SomeClass
	{
            public static void Main(string[] args)
            {
                Computer facade = new Computer();
                facade.StartComputer();
            }
        }
}

Python

# Complex parts
class CPU:
    def freeze(self): pass
    def jump(self, position): pass
    def execute(self): pass
 
class Memory:
    def load(self, position, data): pass
 
class HardDrive:
    def read(self, lba, size): pass
 
# Facade
class Computer:
    def __init__(self):
        self.cpu = CPU()
        self.memory = Memory()
        self.hard_drive = HardDrive()
    
    def start_computer(self):
        self.cpu.freeze()
        self.memory.load(0, self.hard_drive.read(0, 1024))
        self.cpu.jump(10)
        self.cpu.execute()
 
# Client
if __name__ == '__main__':
    facade = Computer()
    facade.start_computer()

PHP

/* Complex parts */
class CPU
{
    public function freeze() { /* ... */ }
    public function jump( $position ) { /* ... */ }
    public function execute() { /* ... */ }

}

class Memory
{
    public function load( $position, $data ) { /* ... */ }
}

class HardDrive
{
    public function read( $lba, $size ) { /* ... */ }
}

/* Facade */
class Computer
{
    protected $cpu = null;
    protected $memory = null;
    protected $hardDrive = null;

    public function __construct()
    {
        $this->cpu = new CPU();
        $this->memory = new Memory();
        $this->hardDrive = new HardDrive();
    }

    public function startComputer()
    {
        $this->cpu->freeze();
        $this->memory->load( BOOT_ADDRESS, $this->hardDrive->read( BOOT_SECTOR, SECTOR_SIZE ) );
        $this->cpu->jump( BOOT_ADDRESS );
        $this->cpu->execute();
    }
}

/* Client */
$facade = new Computer();
$facade->startComputer();

Javascript

Uses Firebug.

/* Complex parts */
var CPU = function () {};
CPU.prototype = {
  freeze: function () {
    console.log('CPU: freeze');
  },
  jump: function (position) {
    console.log('CPU: jump to ' + position);
  },
  execute: function () {
    console.log('CPU: execute');
  }
};

var Memory = function () {};
Memory.prototype = {
  load: function (position, data) {
    console.log('Memory: load "' + data + '" at ' + position);
  }
};

var HardDrive = function () {};
HardDrive.prototype = {
  read: function (lba, size) {
    console.log('HardDrive: read sector ' + lba + '(' + size + ' bytes)');
    return 'hdd data';
  }
};


/* Facade */
var Computer = function () {
  var cpu, memory, hardDrive;
  
  cpu = new CPU();
  memory = new Memory();
  hardDrive = new HardDrive();

  var constant = function (name) {
    var constants = {
      BOOT_ADDRESS: 0,
      BOOT_SECTOR: 0,
      SECTOR_SIZE: 512
    };

    return constants[name];
  };

  this.startComputer = function () {
    cpu.freeze();
    memory.load(constant('BOOT_ADDRESS'), hardDrive.read(constant('BOOT_SECTOR'), constant('SECTOR_SIZE')));
    cpu.jump(constant('BOOT_ADDRESS'));
    cpu.execute();
  }

};

/* Client */
var facade = new Computer();
facade.startComputer();

Нэмэлт холбоосууд

• Description from the Portland Pattern Repository
• Description from the Net Objectives Repository