IEnumerable インターフェイスとは何？わかりやすく解説 Weblio辞書

.NET Framework クラスライブラリリファレンス

索引トップ用語の索引ランキング

IEnumerable インターフェイス

非ジェネリックコレクションに対する単純な反復処理をサポートする列挙子を公開します。

名前空間: System.Collections
アセンブリ: mscorlib (mscorlib.dll 内)
構文

Visual Basic (宣言)

<ComVisibleAttribute(True)> _
<GuidAttribute("496B0ABE-CDEE-11d3-88E8-00902754C43A")>
 _
Public Interface IEnumerable

Visual Basic (使用法)

Dim instance As IEnumerable

[ComVisibleAttribute(true)] 
[GuidAttribute("496B0ABE-CDEE-11d3-88E8-00902754C43A")] 
public interface IEnumerable

C++

[ComVisibleAttribute(true)] 
[GuidAttribute(L"496B0ABE-CDEE-11d3-88E8-00902754C43A")] 
public interface class IEnumerable

/** @attribute ComVisibleAttribute(true) */ 
/** @attribute GuidAttribute("496B0ABE-CDEE-11d3-88E8-00902754C43A") */
 
public interface IEnumerable

JScript

ComVisibleAttribute(true) 
GuidAttribute("496B0ABE-CDEE-11d3-88E8-00902754C43A") 
public interface IEnumerable

解説

このインターフェイスのジェネリックバージョンについては、「System.Collections.Generic.IEnumerable」を参照してください。

実装時の注意 Microsoft Visual Basic の foreach セマンティクスをサポートするには、IEnumerable を実装する必要があります。COM クラスで列挙子を使用できるようにする場合も、このインターフェイスを実装します。

使用例

カスタムコレクションでの IEnumerable インターフェイスと IEnumerator インターフェイスの実装を次のコード例に示します。この例では、これらのインターフェイスのメンバが明示的に呼び出されていませんが、foreach (Visual Basic では for each) の使用によるコレクションの反復処理をサポートするために実装されています。

Visual Basic

Imports System
Imports System.Collections

Public Class Person

    Public Sub New(ByVal
 fName As String, ByVal
 lName As String)
        Me.firstName = fName
        Me.lastName = lName
    End Sub


    Public firstName As String
    Public lastName As String
End Class

Public Class People
    Implements IEnumerable

    Private _people() As Person

    Public Sub New(ByVal
 pArray() As Person)
        _people = New Person(pArray.Length - 1) {}

        Dim i As Integer
        For i = 0 To pArray.Length - 1
            _people(i) = pArray(i)
        Next i
    End Sub

    Public Function GetEnumerator() As
 IEnumerator _
      Implements IEnumerable.GetEnumerator

        Return New PeopleEnum(_people)
    End Function

End Class

Public Class PeopleEnum
    Implements IEnumerator

    Public _people() As Person

    ' Enumerators are positioned before the first element
    ' until the first MoveNext() call.
    Dim position As Integer
 = -1

    Public Sub New(ByVal
 list() As Person)
        _people = list
    End Sub

    Public Function MoveNext() As
 Boolean Implements IEnumerator.MoveNext
        position = position + 1
        Return (position < _people.Length)
    End Function

    Public Sub Reset() Implements
 IEnumerator.Reset
        position = -1
    End Sub

    Public ReadOnly Property
 Current() As Object Implements
 IEnumerator.Current
        Get
            Try
                Return _people(position)
            Catch ex As IndexOutOfRangeException
                Throw New InvalidOperationException()
            End Try
        End Get
    End Property
End Class

Class App
    Shared Sub Main()
        Dim peopleArray() As Person = { _
            New Person("John",
 "Smith"), _
            New Person("Jim", "Johnson"),
 _
            New Person("Sue", "Rabon")}

        Dim peopleList As New
 People(peopleArray)
        Dim p As Person
        For Each p In peopleList
            Console.WriteLine(p.firstName + " " +
 p.lastName)
        Next

    End Sub
End Class

' This code produces output similar to the following:
' 
' John Smith
' Jim Johnson
' Sue Rabon

using System;
using System.Collections;

public class Person
{
    public Person(string fName, string
 lName)
    {
        this.firstName = fName;
        this.lastName = lName;
    }

    public string firstName;
    public string lastName;
}

public class People : IEnumerable
{
    private Person[] _people;
    public People(Person[] pArray)
    {
        _people = new Person[pArray.Length];

        for (int i = 0; i < pArray.Length;
 i++)
        {
            _people[i] = pArray[i];
        }
    }

    public IEnumerator GetEnumerator()
    {
        return new PeopleEnum(_people);
    }
}

public class PeopleEnum : IEnumerator
{
    public Person[] _people;

    // Enumerators are positioned before the first element
    // until the first MoveNext() call.
    int position = -1;

    public PeopleEnum(Person[] list)
    {
        _people = list;
    }

    public bool MoveNext()
    {
        position++;
        return (position < _people.Length);
    }

    public void Reset()
    {
        position = -1;
    }

    public object Current
    {
        get
        {
            try
            {
                return _people[position];
            }
            catch (IndexOutOfRangeException)
            {
                throw new InvalidOperationException();
            }
        }
    }
}

class App
{
    static void Main()
    {
        Person[] peopleArray = new Person[3]
        {
            new Person("John", "Smith"),
            new Person("Jim", "Johnson"),
            new Person("Sue", "Rabon"),
        };

        People peopleList = new People(peopleArray);
        foreach (Person p in peopleList)
            Console.WriteLine(p.firstName + " " + p.lastName);

    }
}

/* This code produces output similar to the following:
 * 
 * John Smith
 * Jim Johnson
 * Sue Rabon
 * 
 */