프로퍼티 (프로그래밍)

'''프로퍼티'''(property)는 일부 객체 지향 프로그래밍 언어에서 필드(데이터 멤버)와 메소드 간 기능의 중간인 클래스 멤버의 특수한 유형이다. 프로퍼티의 읽기와 쓰기는 일반적으로 게터(getter)와 세터(setter) 메소드 호출로 변환된다.
프로퍼티를 지원하는 프로그래밍 언어에는 액션스크립트 3, C#, D, 델파이/프리 파스칼, eC, 코틀린, 자바스크립트, 오브젝티브-C 2.0, 파이썬, 스칼라, 스위프트, 루아, 비주얼 베이직이 있다.
자바, C++과 같은 일부 객체 지향 언어들은 프로퍼티를 지원하지 않기 때문에 프로그래머가 한 쌍의 액세서(accessor)와 뮤테이터(mutator) 메소드를 대신 정의해야 한다.
=== C# ===
class Pen 
{
    private int color; // private field
    
    // public property
    public int Color 
    {  
        get
        {
            return this.color;
        }
        set 
        {
            if (value > 0) {
                this.color = value;
            }
        }
    }
}
// accessing:
Pen pen = new Pen();
int color_tmp = 0;
// ...
pen.Color = 17;
color_tmp = pen.Color;
// ...
pen.Color = ~pen.Color; // bitwise complement ...
// another silly example:
pen.Color += 1; // a lot clearer than "pen.set_Color(pen.get_Color() + 1)"!
class Shape 
{
    
    public Int32 Height { get; set; }
    public Int32 Width  { get; private set; }
    
}
=== C++ ===
#include 
template  class property {
        T value;
    public:
        T & operator = (const T &i) {
            return value = i;
        }
        // This template class member function template serves the purpose to make
        // typing more strict. Assignment to this is only possible with exact identical
        // types.
        template  T2 & operator = (const T2 &i) {
            T2 &guard = value;
            throw guard; // Never reached.
        }
        // Implicit conversion back to T. 
        operator T const & () const {
            return value;
        }
};
struct Foo {
    // Properties using unnamed classes.
    class {
            int value;
        public:
            int & operator = (const int &i) { return value = i; }
            operator int () const { return value; }
    } alpha;
    class {
            float value;
        public:
            float & operator = (const float &f) { return value = f; }
            operator float () const { return value; }
    } bravo;
};
struct Bar {
    // Using the property-template.
    property  alpha;
    property  bravo;
};
int main () {
    Foo foo;
    foo.alpha = 5;
    foo.bravo = 5.132f;
    Bar bar;
    bar.alpha = true;
    bar.bravo = true; // This line will yield a compile time error
                      // due to the guard template member function.
    ::std::cout 
==== C++, Microsoft & C++Builder-specific ====
예시 출처: MSDN  설명 문서
// declspec_property.cpp
struct S
{
   int i;
   void putprop(int j)
   { 
      i = j;
   }
   int getprop()
   {
      return i;
   }
   __declspec(property(get = getprop, put = putprop)) int the_prop;
};
int main()
{
   S s;
   s.the_prop = 5;
   return s.the_prop;
}
=== D ===
class Pen
{
    private int m_color; // private field
    
    // public get property
    public int color () {
        return m_color;
    }
    
    // public set property
    public void color (int value) {
         m_color = value;
    }
}
auto pen = new Pen;
pen.color = ~pen.color; // bitwise complement
// the set property can also be used in expressions, just like regular assignment
int theColor = (pen.color = 0xFF0000);
In D version 2, each property accessor or mutator must be marked with @property:
class Pen
{
    private int m_color; // private field
    
    // public get property
    @property public int color () {
        return m_color;
    }
    
    // public set property
    @property public void color (int value) {
        m_color = value;
    }
}
=== Delphi/Free Pascal ===
type TPen = class
  private
    FColor: TColor;
    function GetColor: TColor;
    procedure SetColor(const AValue: TColor);
  public
    property Color: Integer read GetColor write SetColor;
end;
function TPen.GetColor: TColor;
begin
  Result := FColor;
end;
procedure TPen.SetColor(const AValue: TColor);
begin
  if FColor  AValue
   then FColor := AValue;
end;
// accessing:
var Pen: TPen;
// ...
Pen.Color := not Pen.Color;
(*
Delphi also supports a 'direct field' syntax -
property Color: TColor read FColor write SetColor;
or
property Color: TColor read GetColor write FColor;
where the compiler generates the exact same code as for reading and writing
a field. This offers the efficiency of a field, with the safety of a property.
(You can't get a pointer to the property, and you can always replace the member
access with a method call.)
*)
=== eC ===
class Pen 
{
   // private data member
   Color color;
public:
   // public property
   property Color color 
   {  
      get { return color; }
      set { color = value; }
   }
}
Pen blackPen { color = black };
Pen whitePen { color = white };
Pen pen3 { color = { 30, 80, 120 } };
Pen pen4 { color = ColorHSV { 90, 20, 40 } };
=== F# ===
type Pen() = class
    let mutable _color = 0
    member this.Color
        with get() = _color
        and set value = _color 
=== JavaScript ===
function Pen() {
    this._color = 0;
}
// Add the property to the Pen type itself, can also
// be set on the instance individually
Object.defineProperties(Pen.prototype, {
    color: {
        get: function () {
            return this._color;
        },
        set: function (value) {
            this._color = value;
        }
    }
});
var pen = new Pen();
pen.color = ~pen.color; // bitwise complement
pen.color += 1; // Add one
=== ActionScript 3.0 ===
package  {
	public class Pen {
		private var _color:uint = 0;
		
		public function get color():uint {
			return _color;
		}
		
		public function set color(value:uint):void {
			_color = value;
		}
	}
}
var pen:Pen = new Pen();
pen.color = ~pen.color; // bitwise complement
pen.color += 1; // add one
=== Objective-C 2.0 ===
@interface Pen : NSObject
@property (copy) NSColor *colour;	// The "copy" attribute causes the object's copy to be
					// retained, instead of the original.
@end
@implementation Pen
@synthesize colour;			// Compiler directive to synthesise accessor methods.
					// It can be left behind in Xcode 4.5 and later.
@end
위 예제는 다음과 같이 임의의 메소드 안에 사용이 가능하다:
Pen *pen = Pen alloc init;
pen.colour = NSColor blackColor;
float red = pen.colour.redComponent;
pen.colour drawSwatchInRect: NSMakeRect(0, 0, 100, 100);
=== PHP ===
class Pen
{
    private int $color = 1;
    function __set($property, $value)
    {
        if (property_exists($this, $property)) { 
            $this->$property = $value;
        }
    }
    function __get($property)
    {
        if (property_exists($this, $property)) {
            return $this->$property;
        }
        return null;
    }
}
 
$p = new Pen();
$p->color = ~$p->color; // Bitwise complement
echo $p->color;
=== Python ===
class Pen(object):
    def __init__(self) -> None:
        self._color = 0  # "private" variable
    @property
    def color(self):
        return self._color
    @color.setter
    def color(self, color):
        self._color = color
pen = Pen()
# Accessing:
pen.color = ~pen.color  # Bitwise complement ...
=== Ruby ===
class Pen
  def initialize
    @color = 0
  end
    
  # Defines a getter for the @color field
  def color
    @color
  end
  # Defines a setter for the @color field
  def color=(value)
    @color = value
  end
end
pen = Pen.new
pen.color = ~pen.color    # Bitwise complement
루비는 또한 클래스의 인스턴스 메소드로 정의되는 자동 게터/세터 신시사이저를 제공한다.
class Pen
  attr_reader :brand    # Generates a getter for @brand (Read-Only)
  attr_writer :size     # Generates a setter for @size  (Write-Only)
  attr_accessor :color  # Generates both a getter and setter for @color (Read/Write)
  def initialize
    @color = 0          # Within the object, we can access the instance variable directly
    @brand = "Penbrand"
    @size = 0.7         # But we could also use the setter method defined by the attr_accessor Class instance method
  end
end
pen = Pen.new
puts pen.brand           # Accesses the pen brand through the generated getter
pen.size = 0.5           # Updates the size field of the pen through the generated setter
pen.color = ~pen.color   
=== Visual Basic ===
==== Visual Basic (.NET 2003-2010) ====
Public Class Pen
 
    Private _color As Integer ' Private field
    Public Property Color() As Integer ' Public property
        Get
            Return _color
        End Get
        Set(ByVal value As Integer)
            _color = value
        End Set
    End Property
End Class
' Create Pen class instance
Dim pen As New Pen()
' Set value
pen.Color = 1
' Get value
Dim color As Int32 = pen.Color
==== Visual Basic (only .NET 2010) ====
Public Class Pen
    Public Property Color() As Integer ' Public property
End Class
 
' Create Pen class instance
Dim pen As New Pen()
' Set value
pen.Color = 1
' Get value
Dim color As Int32 = pen.Color
==== Visual Basic 6 ====
' in a class named clsPen
Private m_Color As Long
Public Property Get Color() As Long
    Color = m_Color
End Property
Public Property Let Color(ByVal RHS As Long)
    m_Color = RHS
End Property
' accessing:
Dim pen As New clsPen
' ...
pen.Color = Not pen.Color
* 속성 (컴퓨터 과학)
* 데이터 바인딩
* 인덱서 (프로그래밍)
* 메서드 (컴퓨터 프로그래밍)
* 뮤테이터 메소드
분류:객체 지향 프로그래밍