attributeとは？ わかりやすく解説

<SerializableAttribute> _
<ClassInterfaceAttribute(ClassInterfaceType.None)> _
<ComVisibleAttribute(True)> _
<AttributeUsageAttribute(AttributeTargets.All, Inherited:=True, AllowMultiple:=False)>
 _
Public MustInherit Class
 Attribute
    Implements _Attribute

Dim instance As Attribute

[SerializableAttribute] 
[ClassInterfaceAttribute(ClassInterfaceType.None)] 
[ComVisibleAttribute(true)] 
[AttributeUsageAttribute(AttributeTargets.All, Inherited=true,
 AllowMultiple=false)] 
public abstract class Attribute : _Attribute

[SerializableAttribute] 
[ClassInterfaceAttribute(ClassInterfaceType::None)] 
[ComVisibleAttribute(true)] 
[AttributeUsageAttribute(AttributeTargets::All, Inherited=true,
 AllowMultiple=false)] 
public ref class Attribute abstract : _Attribute

/** @attribute SerializableAttribute() */ 
/** @attribute ClassInterfaceAttribute(ClassInterfaceType.None) */ 
/** @attribute ComVisibleAttribute(true) */ 
/** @attribute AttributeUsageAttribute(AttributeTargets.All, Inherited=true,
 AllowMultiple=false) */ 
public abstract class Attribute implements
 _Attribute

SerializableAttribute 
ClassInterfaceAttribute(ClassInterfaceType.None) 
ComVisibleAttribute(true) 
AttributeUsageAttribute(AttributeTargets.All, Inherited=true,
 AllowMultiple=false) 
public abstract class Attribute implements
 _Attribute

Imports System
Imports System.Reflection

Public Module CustomAttrVB

    ' An enumeration of animals. Start at 1 (0 = uninitialized).
    Public Enum Animal
        ' Pets
        Dog = 1
        Cat
        Bird
    End Enum

    ' Visual Basic requires the AttributeUsage be specified.
    ' A custom attribute to allow a target to have a pet.
    <AttributeUsage(AttributeTargets.Method)> _
    Public Class AnimalTypeAttribute
        Inherits Attribute

        ' The constructor is called when the attribute is set.
        Public Sub New(ByVal
 animal As Animal)
            Me.thePet = animal
        End Sub

        ' Keep a variable internally ...
        Protected thePet As Animal

        ' .. and show a copy to the outside world.
        Public Property Pet() As
 Animal
            Get
                Return thePet
            End Get
            Set(ByVal Value As
 Animal)
                thePet = Value
            End Set
        End Property

    End Class

    ' A test class where each method has its own pet.
    Class AnimalTypeTestClass

        <AnimalType(Animal.Dog)> _
        Public Sub DogMethod()
        End Sub

        <AnimalType(Animal.Cat)> _
        Public Sub CatMethod()
        End Sub

        <AnimalType(Animal.Bird)> _
        Public Sub BirdMethod()
        End Sub
    End Class

    ' The runtime test.
    Sub Main()
        Dim testClass As New
 AnimalTypeTestClass()
        Dim tcType As Type = testClass.GetType()
        Dim mInfo As MethodInfo
        ' Iterate through all the methods of the class.
        For Each mInfo In
 tcType.GetMethods()
            Dim attr As Attribute
            ' Iterate through all the attributes of the method.
            For Each attr In
 Attribute.GetCustomAttributes(mInfo)
                If TypeOf attr Is
 AnimalTypeAttribute Then
                    Dim attrCustom As AnimalTypeAttribute
 = _
                        CType(attr, AnimalTypeAttribute)
                    Console.WriteLine("Method {0} has a pet {1}
 attribute.", _
                         mInfo.Name(), attrCustom.Pet.ToString())
                End If
            Next
        Next
    End Sub
End Module

' Output:
' Method DogMethod has a pet Dog attribute.
' Method CatMethod has a pet Cat attribute.
' Method BirdMethod has a pet Bird attribute.

using System;
using System.Reflection;

namespace CustomAttrCS {
    // An enumeration of animals. Start at 1 (0 = uninitialized).
    public enum Animal {
        // Pets.
        Dog = 1,
        Cat,
        Bird,
    }

    // A custom attribute to allow a target to have a pet.
    public class AnimalTypeAttribute : Attribute
 {
        // The constructor is called when the attribute is set.
        public AnimalTypeAttribute(Animal pet) {
            thePet = pet;
        }

        // Keep a variable internally ...
        protected Animal thePet;

        // .. and show a copy to the outside world.
        public Animal Pet {
            get { return thePet; }
            set { thePet = Pet; }
        }
    }

    // A test class where each method has its own pet.
    class AnimalTypeTestClass {
        [AnimalType(Animal.Dog)]
        public void DogMethod() {}

        [AnimalType(Animal.Cat)]
        public void CatMethod() {}

        [AnimalType(Animal.Bird)]
        public void BirdMethod() {}
    }

    class DemoClass {
        static void Main(string[]
 args) {
            AnimalTypeTestClass testClass = new AnimalTypeTestClass();
            Type type = testClass.GetType();
            // Iterate through all the methods of the class.
            foreach(MethodInfo mInfo in type.GetMethods())
 {
                // Iterate through all the Attributes for each method.
                foreach (Attribute attr in
 
                    Attribute.GetCustomAttributes(mInfo)) {
                    // Check for the AnimalType attribute.
                    if (attr.GetType() == typeof(AnimalTypeAttribute))
                        Console.WriteLine(
                            "Method {0} has a pet {1} attribute.", 
                            mInfo.Name, ((AnimalTypeAttribute)attr).Pet);
                }

            }
        }
    }
}

/*
 * Output:
 * Method DogMethod has a pet Dog attribute.
 * Method CatMethod has a pet Cat attribute.
 * Method BirdMethod has a pet Bird attribute.
 */

using namespace System;
using namespace System::Reflection;

// An enumeration of animals. Start at 1 (0 = uninitialized).
public enum class Animal
{
   // Pets.
   Dog = 1,
   Cat, Bird
};

// A custom attribute to allow a target to have a pet.
public ref class AnimalTypeAttribute: public
 Attribute
{
public:

   // The constructor is called when the attribute is set.
   AnimalTypeAttribute( Animal pet )
   {
      thePet = pet;
   }


protected:

   // Keep a variable internally ...
   Animal thePet;

public:

   property Animal Pet 
   {
      // .. and show a copy to the outside world.
      Animal get()
      {
         return thePet;
      }

      void set( Animal value )
      {
         thePet = value;
      }
   }
};

// A test class where each method has its own pet.
ref class AnimalTypeTestClass
{
public:

   [AnimalType(Animal::Dog)]
   void DogMethod(){}


   [AnimalType(Animal::Cat)]
   void CatMethod(){}

   [AnimalType(Animal::Bird)]
   void BirdMethod(){}

};

int main()
{
   AnimalTypeTestClass^ testClass = gcnew AnimalTypeTestClass;
   Type^ type = testClass->GetType();

   // Iterate through all the methods of the class.
   System::Collections::IEnumerator^ myEnum = type->GetMethods()->GetEnumerator();
   while ( myEnum->MoveNext() )
   {
      MethodInfo^ mInfo = safe_cast<MethodInfo^>(myEnum->Current);

      // Iterate through all the Attributes for each method.
      System::Collections::IEnumerator^ myEnum1 = Attribute::GetCustomAttributes(
 mInfo )->GetEnumerator();
      while ( myEnum1->MoveNext() )
      {
         Attribute^ attr = safe_cast<Attribute^>(myEnum1->Current);

         // Check for the AnimalType attribute.
         if ( attr->GetType() == AnimalTypeAttribute::typeid
 )
                  Console::WriteLine( "Method {0} has a pet {1} attribute.",
 mInfo->Name, (dynamic_cast<AnimalTypeAttribute^>(attr))->Pet );
      }
   }
}

/*
 * Output:
 * Method DogMethod has a pet Dog attribute.
 * Method CatMethod has a pet Cat attribute.
 * Method BirdMethod has a pet Bird attribute.
 */

package CustomAttrJSL; 

import System.*;
import System.Reflection.*;
  
public class Animal
{
    protected int pet;
    public static final int
 dog = 1;
    public static final int
 cat = 2;
    public static final int
 bird = 3;

    public Animal()
    {
        pet = 0;
    } //Animal
    public Animal(int p)
    {
        pet = p;
    } //Animal
    public String getPet()
    {
        switch (pet) {
            case 1 :
                return "Dog";
            case 2 :
                return "Cat";
            case 3 :
                return "Bird";
            default :
                return null;
        }
    } //getPet
} //Animal
      
// A custom attribute to allow a target to have a pet.
/** @attribute System.AttributeUsageAttribute(AttributeTargets.Method)
 */
public class AnimalTypeAttribute extends Attribute
{
    public AnimalTypeAttribute() { }
    // The constructor is called when the attribute is set.
    public AnimalTypeAttribute(int pet)
    {
        thePet = new Animal(pet);
    } //AnimalTypeAttribute

    // Keep a variable internally...
    protected Animal thePet;

    //.. and show a copy to the outside world.
    /** @property 
     */
    public Animal get_Pet()
    {
        return thePet;
    } //get_Pet

    /** @property 
     */
    public void set_Pet(Animal value)
    {
        thePet = value;
    } //set_Pet
} //AnimalTypeAttribute
      
 // A test class where each method has its own pet.
class AnimalTypeTestClass
{
    /** @attribute AnimalType(Animal.dog)
     */
    public void DogMethod()
    {
    } //DogMethod

    /** @attribute AnimalType(Animal.cat)
     */
    public void CatMethod()
    {
    } //CatMethod

    /** @attribute AnimalType(Animal.bird)
     */
    public void BirdMethod()
    {
    } //BirdMethod
} //AnimalTypeTestClass
   
class DemoClass
{
    public static void main(String[]
 args)
    {
        AnimalTypeTestClass testClass = new AnimalTypeTestClass();
        Type type = testClass.GetType();
        // Iterate through all the methods of the class.
        for (int iCtr1 = 0; iCtr1 < type.GetMethods().length;
 iCtr1++) {
            MethodInfo mInfo = type.GetMethods()[iCtr1];
            // Iterate through all the Attributes for each method.
            for (int iCtr2 = 0; 
                iCtr2 < Attribute.GetCustomAttributes(mInfo).length; 
                iCtr2++) {
               
                Attribute attr = Attribute.GetCustomAttributes(mInfo)[iCtr2];
                // Check for the AnimalType attribute.
                if (attr.GetType().
                    Equals(AnimalTypeAttribute.class.ToType()))
 {                
                    Console.WriteLine("Method {0} has a pet {1} attribute.",
 
                        mInfo.get_Name(), 
                        ((AnimalTypeAttribute)attr).get_Pet().getPet());
                }
            }
        }
    } //main
} //DemoClass 

/*
 Output:
 Method DogMethod has a pet Dog attribute.
 Method CatMethod has a pet Cat attribute.
 Method BirdMethod has a pet Bird attribute.
*/

import System;
import System.Reflection;
import CustomAttrJS;

package CustomAttrJS {
    // An enumeration of animals. Start at 1 (0 = uninitialized).
    public enum Animal {
        // Pets.
        Dog = 1,
        Cat,
        Bird,
    }

    // A custom attribute to allow a target to have a pet.
    public AttributeUsage(AttributeTargets.Method) class
 AnimalTypeAttribute extends Attribute {
        // The constructor is called when the attribute is set.
        public function AnimalTypeAttribute(pet
 : Animal) {
            thePet = pet;
        }

        // Keep a variable internally ...
        protected var thePet : Animal;

        // .. and show a copy to the outside world.
        public function get
 Pet() : Animal {
                    return thePet; 
                }
        
                public function set
 Pet(pet : Animal) {
                    thePet = pet; 
                }
    }

    // A test class where each method has its own pet.
    class AnimalTypeTestClass {
        public AnimalTypeAttribute(Animal.Dog) 
                function DogMethod() {}

        public AnimalTypeAttribute(Animal.Cat)
        function CatMethod() {}

        public AnimalTypeAttribute(Animal.Bird)
        function BirdMethod() {}
    }
}



var testClass : AnimalTypeTestClass = new AnimalTypeTestClass();
var type : Type = testClass.GetType();
// Iterate through all the methods of the class.
            var mInfo : MethodInfo[] = type.GetMethods();
for (var i : int = 0; i
 < mInfo.length; i++) {
    // Iterate through all the Attributes for each method.
                    var attr : Attribute[] = Attribute.GetCustomAttributes(mInfo[i]);
    for (var j : int = 0;
 j < attr.length; j++) 
    {
        // Check for the AnimalType attribute.
        if (attr[j].GetType() == AnimalTypeAttribute)
            Console.WriteLine(
                "Method {0} has a pet {1} attribute.", 
                mInfo[i].Name, AnimalTypeAttribute(attr[j]).Pet);
    }

}


/*
 * Output:
 * Method BirdMethod has a pet Bird attribute.
 * Method CatMethod has a pet Cat attribute.
 * Method DogMethod has a pet Dog attribute.
 *
 */

Protected Sub New

Dim instance As New Attribute

protected Attribute ()

protected:
Attribute ()

protected Attribute ()

protected function Attribute ()

' Define a custom parameter attribute that takes a single message argument.
<AttributeUsage(AttributeTargets.Parameter)>  _
Public Class ArgumentUsageAttribute
    Inherits Attribute
       
    ' This is the attribute constructor.
    Public Sub New(UsageMsg
 As String)
        Me.usageMsg = UsageMsg
    End Sub ' New

    ' usageMsg is storage for the attribute message.
    Protected usageMsg As String
       
    ' This is the Message property for the attribute.
    Public Property Message() As
 String
        Get
            Return usageMsg
        End Get
        Set
            usageMsg = value
        End Set
    End Property
End Class ' ArgumentUsageAttribute
 

// Define a custom parameter attribute that takes a single message argument.
[AttributeUsage( AttributeTargets.Parameter )]
public class ArgumentUsageAttribute : Attribute
{
    // This is the attribute constructor.
    public ArgumentUsageAttribute( string UsageMsg
 )
    {
        this.usageMsg = UsageMsg;
    }

    // usageMsg is storage for the attribute message.
    protected string usageMsg;

    // This is the Message property for the attribute.
    public string Message
    {
        get { return usageMsg; }
        set { usageMsg = value; }
    }
}

// Define a custom parameter attribute that takes a single message argument.

[AttributeUsage(AttributeTargets::Parameter)]
public ref class ArgumentUsageAttribute: public
 Attribute
{
protected:

   // usageMsg is storage for the attribute message.
   String^ usageMsg;

public:

   // This is the attribute constructor.
   ArgumentUsageAttribute( String^ UsageMsg )
   {
      this->usageMsg = UsageMsg;
   }


   property String^ Message 
   {
      // This is the Message property for the attribute.
      String^ get()
      {
         return usageMsg;
      }

      void set( String^ value )
      {
         this->usageMsg = value;
      }
   }
};

// Define a custom parameter attribute that takes a single message argument.
/** @attribute AttributeUsage(AttributeTargets.Parameter)
 */
public class ArgumentUsageAttribute extends
 Attribute
{
    // This is the attribute constructor.
    public ArgumentUsageAttribute(String usgMsg)
    {
        this.usageMsg = usgMsg;
    } //ArgumentUsageAttribute

    // usageMsg is storage for the attribute message.
    protected String usageMsg;

    // This is the Message property for the attribute.
    /** @property 
     */
    public String get_Message()
    {
        return usageMsg;
    } //get_Message

    /** @property 
     */
    public void set_Message(String value)
    {
        usageMsg = value;
    } //set_Message
} //ArgumentUsageAttribute  

<ComVisibleAttribute(True)> _
<GuidAttribute("917B14D0-2D9E-38B8-92A9-381ACF52F7C0")>
 _
<InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)> _
<CLSCompliantAttribute(False)> _
Public Interface _Attribute

Dim instance As _Attribute

[ComVisibleAttribute(true)] 
[GuidAttribute("917B14D0-2D9E-38B8-92A9-381ACF52F7C0")] 
[InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown)] 
[CLSCompliantAttribute(false)] 
public interface _Attribute

[ComVisibleAttribute(true)] 
[GuidAttribute(L"917B14D0-2D9E-38B8-92A9-381ACF52F7C0")] 
[InterfaceTypeAttribute(ComInterfaceType::InterfaceIsIUnknown)] 
[CLSCompliantAttribute(false)] 
public interface class _Attribute

/** @attribute ComVisibleAttribute(true) */ 
/** @attribute GuidAttribute("917B14D0-2D9E-38B8-92A9-381ACF52F7C0") */
 
/** @attribute InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown) */ 
/** @attribute CLSCompliantAttribute(false) */ 
public interface _Attribute

ComVisibleAttribute(true) 
GuidAttribute("917B14D0-2D9E-38B8-92A9-381ACF52F7C0") 
InterfaceTypeAttribute(ComInterfaceType.InterfaceIsIUnknown) 
CLSCompliantAttribute(false) 
public interface _Attribute