IComparable<T> インターフェイス

定義

インスタンスの並べ替えなどを目的とし、型固有の比較メソッドを作成するために値型またはクラスで実装する、汎用の比較メソッドを定義します。Defines a generalized comparison method that a value type or class implements to create a type-specific comparison method for ordering or sorting its instances.

generic <typename T>
public interface class IComparable
public interface IComparable<in T>
public interface IComparable<T>
type IComparable<'T> = interface
Public Interface IComparable(Of In T)
Public Interface IComparable(Of T)

型パラメーター

T

比較するオブジェクトの型。The type of object to compare.

この型パラメーターは反変です。 つまり、指定した型、または弱い派生型のいずれかを使用することができます。 共変性および反変性の詳細については、「ジェネリックの共変性と反変性」をご覧ください。
派生

次の例は、単純な Temperature オブジェクトの IComparable<T> を実装する方法を示しています。The following example illustrates the implementation of IComparable<T> for a simple Temperature object. この例では、Temperature オブジェクトキーを使用して文字列の SortedList<TKey,TValue> コレクションを作成し、一連の温度と文字列を順番にリストに追加します。The example creates a SortedList<TKey,TValue> collection of strings with Temperature object keys, and adds several pairs of temperatures and strings to the list out of sequence. Add メソッドの呼び出しでは、SortedList<TKey,TValue> コレクションは IComparable<T> の実装を使用してリストエントリを並べ替えます。このエントリは、気温の増加順に表示されます。In the call to the Add method, the SortedList<TKey,TValue> collection uses the IComparable<T> implementation to sort the list entries, which are then displayed in order of increasing temperature.

#using <System.dll>

using namespace System;
using namespace System::Collections::Generic;

public ref class Temperature: public IComparable<Temperature^> {

protected:
   // The underlying temperature value.
   Double m_value;

public:
   // Implement the generic CompareTo method with the Temperature class 
   // as the Type parameter. 
   virtual Int32 CompareTo( Temperature^ other ) {
   
      // If other is not a valid object reference, this instance 
      // is greater.
      if (other == nullptr) return 1;
      
      // The temperature comparison depends on the comparison of the
      // the underlying Double values. 
      return m_value.CompareTo( other->m_value );
   }

       // Define the is greater than operator.
    bool operator>=  (Temperature^ other)
    {
       return CompareTo(other) == 1;
    }
    
    // Define the is less than operator.
    bool operator<  (Temperature^ other)
    {
       return CompareTo(other) == -1;
    }
    
       // Define the is greater than or equal to operator.
    bool operator>  (Temperature^ other)
    {
       return CompareTo(other) >= 0;
    }
    
    // Define the is less than or equal to operator.
    bool operator<=  (Temperature^ other)
    {
       return CompareTo(other) <= 0;
    }

   property Double Celsius {
      Double get() {
         return m_value + 273.15;
      }
   }

   property Double Kelvin {
      Double get() {
         return m_value;
      }
      void set( Double value ) {
         if (value < 0)
            throw gcnew ArgumentException("Temperature cannot be less than absolute zero.");
         else
            m_value = value;
      }
   }

   Temperature(Double kelvins) {
      this->Kelvin = kelvins;
   }
};

int main() {
   SortedList<Temperature^, String^>^ temps = 
      gcnew SortedList<Temperature^, String^>();

   // Add entries to the sorted list, out of order.
   temps->Add(gcnew Temperature(2017.15), "Boiling point of Lead");
   temps->Add(gcnew Temperature(0), "Absolute zero");
   temps->Add(gcnew Temperature(273.15), "Freezing point of water");
   temps->Add(gcnew Temperature(5100.15), "Boiling point of Carbon");
   temps->Add(gcnew Temperature(373.15), "Boiling point of water");
   temps->Add(gcnew Temperature(600.65), "Melting point of Lead");

   for each( KeyValuePair<Temperature^, String^>^ kvp in temps )
   {
      Console::WriteLine("{0} is {1} degrees Celsius.", kvp->Value, kvp->Key->Celsius);
   }
}
/* The example displays the following output:
      Absolute zero is 273.15 degrees Celsius.
      Freezing point of water is 546.3 degrees Celsius.
      Boiling point of water is 646.3 degrees Celsius.
      Melting point of Lead is 873.8 degrees Celsius.
      Boiling point of Lead is 2290.3 degrees Celsius.
      Boiling point of Carbon is 5373.3 degrees Celsius.
*/
using System;
using System.Collections.Generic;

public class Temperature : IComparable<Temperature>
{
    // Implement the generic CompareTo method with the Temperature
    // class as the Type parameter.
    //
    public int CompareTo(Temperature other)
    {
        // If other is not a valid object reference, this instance is greater.
        if (other == null) return 1;

        // The temperature comparison depends on the comparison of
        // the underlying Double values.
        return m_value.CompareTo(other.m_value);
    }

    // Define the is greater than operator.
    public static bool operator >  (Temperature operand1, Temperature operand2)
    {
       return operand1.CompareTo(operand2) == 1;
    }

    // Define the is less than operator.
    public static bool operator <  (Temperature operand1, Temperature operand2)
    {
       return operand1.CompareTo(operand2) == -1;
    }

    // Define the is greater than or equal to operator.
    public static bool operator >=  (Temperature operand1, Temperature operand2)
    {
       return operand1.CompareTo(operand2) >= 0;
    }

    // Define the is less than or equal to operator.
    public static bool operator <=  (Temperature operand1, Temperature operand2)
    {
       return operand1.CompareTo(operand2) <= 0;
    }

    // The underlying temperature value.
    protected double m_value = 0.0;

    public double Celsius
    {
        get
        {
            return m_value - 273.15;
        }
    }

    public double Kelvin
    {
        get
        {
            return m_value;
        }
        set
        {
            if (value < 0.0)
            {
                throw new ArgumentException("Temperature cannot be less than absolute zero.");
            }
            else
            {
                m_value = value;
            }
        }
    }

    public Temperature(double kelvins)
    {
        this.Kelvin = kelvins;
    }
}

public class Example
{
    public static void Main()
    {
        SortedList<Temperature, string> temps =
            new SortedList<Temperature, string>();

        // Add entries to the sorted list, out of order.
        temps.Add(new Temperature(2017.15), "Boiling point of Lead");
        temps.Add(new Temperature(0), "Absolute zero");
        temps.Add(new Temperature(273.15), "Freezing point of water");
        temps.Add(new Temperature(5100.15), "Boiling point of Carbon");
        temps.Add(new Temperature(373.15), "Boiling point of water");
        temps.Add(new Temperature(600.65), "Melting point of Lead");

        foreach( KeyValuePair<Temperature, string> kvp in temps )
        {
            Console.WriteLine("{0} is {1} degrees Celsius.", kvp.Value, kvp.Key.Celsius);
        }
    }
}
/* This example displays the following output:
      Absolute zero is -273.15 degrees Celsius.
      Freezing point of water is 0 degrees Celsius.
      Boiling point of water is 100 degrees Celsius.
      Melting point of Lead is 327.5 degrees Celsius.
      Boiling point of Lead is 1744 degrees Celsius.
      Boiling point of Carbon is 4827 degrees Celsius.
*/
Imports System.Collections.Generic

Public Class Temperature
    Implements IComparable(Of Temperature)

    ' Implement the generic CompareTo method with the Temperature class 
    ' as the type parameter. 
    '
    Public Overloads Function CompareTo(ByVal other As Temperature) As Integer _
        Implements IComparable(Of Temperature).CompareTo

        ' If other is not a valid object reference, this instance is greater.
        If other Is Nothing Then Return 1
        
        ' The temperature comparison depends on the comparison of the
        ' the underlying Double values. 
        Return m_value.CompareTo(other.m_value)
    End Function
    
    ' Define the is greater than operator.
    Public Shared Operator >  (operand1 As Temperature, operand2 As Temperature) As Boolean
       Return operand1.CompareTo(operand2) = 1
    End Operator
    
    ' Define the is less than operator.
    Public Shared Operator <  (operand1 As Temperature, operand2 As Temperature) As Boolean
       Return operand1.CompareTo(operand2) = -1
    End Operator

    ' Define the is greater than or equal to operator.
    Public Shared Operator >=  (operand1 As Temperature, operand2 As Temperature) As Boolean
       Return operand1.CompareTo(operand2) >= 0
    End Operator
    
    ' Define the is less than operator.
    Public Shared Operator <=  (operand1 As Temperature, operand2 As Temperature) As Boolean
       Return operand1.CompareTo(operand2) <= 0
    End Operator

    ' The underlying temperature value.
    Protected m_value As Double = 0.0

    Public ReadOnly Property Celsius() As Double
        Get
            Return m_value - 273.15
        End Get
    End Property

    Public Property Kelvin() As Double
        Get
            Return m_value
        End Get
        Set(ByVal Value As Double)
            If value < 0.0 Then 
                Throw New ArgumentException("Temperature cannot be less than absolute zero.")
            Else
                m_value = Value
            End If
        End Set
    End Property

    Public Sub New(ByVal kelvins As Double)
        Me.Kelvin = kelvins 
    End Sub
End Class

Public Class Example
    Public Shared Sub Main()
        Dim temps As New SortedList(Of Temperature, String)

        ' Add entries to the sorted list, out of order.
        temps.Add(New Temperature(2017.15), "Boiling point of Lead")
        temps.Add(New Temperature(0), "Absolute zero")
        temps.Add(New Temperature(273.15), "Freezing point of water")
        temps.Add(New Temperature(5100.15), "Boiling point of Carbon")
        temps.Add(New Temperature(373.15), "Boiling point of water")
        temps.Add(New Temperature(600.65), "Melting point of Lead")

        For Each kvp As KeyValuePair(Of Temperature, String) In temps
            Console.WriteLine("{0} is {1} degrees Celsius.", kvp.Value, kvp.Key.Celsius)
        Next
    End Sub
End Class

' The example displays the following output:
'      Absolute zero is -273.15 degrees Celsius.
'      Freezing point of water is 0 degrees Celsius.
'      Boiling point of water is 100 degrees Celsius.
'      Melting point of Lead is 327.5 degrees Celsius.
'      Boiling point of Lead is 1744 degrees Celsius.
'      Boiling point of Carbon is 4827 degrees Celsius.
'

注釈

このインターフェイスは、値を順序付けまたは並べ替えできる型によって実装され、ジェネリックコレクションオブジェクトのメンバーを順序付けるための厳密に型指定された比較メソッドを提供します。This interface is implemented by types whose values can be ordered or sorted and provides a strongly typed comparison method for ordering members of a generic collection object. たとえば、1つの数値は2番目の数値よりも大きくすることができ、1つの文字列はアルファベット順に表示されます。For example, one number can be larger than a second number, and one string can appear in alphabetical order before another. これを行うには、実装する型が、並べ替え順序における現在のインスタンスの位置が、同じ型の2番目のオブジェクトの前、後、または同じであるかどうかを示す1つのメソッド CompareTo(T)を定義する必要があります。It requires that implementing types define a single method, CompareTo(T), that indicates whether the position of the current instance in the sort order is before, after, or the same as a second object of the same type. 通常、メソッドは開発者コードから直接呼び出されません。Typically, the method is not called directly from developer code. 代わりに、List<T>.Sort()Addなどのメソッドによって自動的に呼び出されます。Instead, it is called automatically by methods such as List<T>.Sort() and Add.

通常、IComparable<T> の実装を提供する型は、IEquatable<T> インターフェイスも実装します。Typically, types that provide an IComparable<T> implementation also implement the IEquatable<T> interface. IEquatable<T> インターフェイスは、実装する型のインスタンスが等しいかどうかを判断する Equals メソッドを定義します。The IEquatable<T> interface defines the Equals method, which determines the equality of instances of the implementing type.

次の表に示すように、CompareTo(T) メソッドの実装では、3つの値のいずれかを持つ Int32 を返す必要があります。The implementation of the CompareTo(T) method must return an Int32 that has one of three values, as shown in the following table.

Value 意味Meaning
ゼロより小さいLess than zero このオブジェクトは、並べ替え順序で CompareTo メソッドによって指定されたオブジェクトの前にあります。This object precedes the object specified by the CompareTo method in the sort order.
ゼロZero この現在のインスタンスは、並べ替え順序において、CompareTo メソッド引数で指定されたオブジェクトと同じ位置に出現します。This current instance occurs in the same position in the sort order as the object specified by the CompareTo method argument.
ゼロより大きいGreater than zero この現在のインスタンスは、並べ替え順序において、CompareTo メソッド引数で指定されたオブジェクトに従います。This current instance follows the object specified by the CompareTo method argument in the sort order.

すべての数値型 (Int32Doubleなど) は、StringCharDateTimeと同様に IComparable<T>を実装します。All numeric types (such as Int32 and Double) implement IComparable<T>, as do String, Char, and DateTime. また、カスタム型には、オブジェクトインスタンスの順序付けまたは並べ替えを可能にするための IComparable<T> の独自の実装が用意されている必要があります。Custom types should also provide their own implementation of IComparable<T> to enable object instances to be ordered or sorted.

注意 (実装者)

IComparable<T> インターフェイスの型パラメーターを、このインターフェイスを実装している型に置き換えます。Replace the type parameter of the IComparable<T> interface with the type that is implementing this interface.

IComparable<T>を実装する場合は、op_GreaterThanop_GreaterThanOrEqualop_LessThan、および op_LessThanOrEqual の各演算子をオーバーロードして、CompareTo(T)と一致する値を返す必要があります。If you implement IComparable<T>, you should overload the op_GreaterThan, op_GreaterThanOrEqual, op_LessThan, and op_LessThanOrEqual operators to return values that are consistent with CompareTo(T). さらに、IEquatable<T>も実装する必要があります。In addition, you should also implement IEquatable<T>. 詳細については、IEquatable<T> に関する記事を参照してください。See the IEquatable<T> article for complete information.

メソッド

CompareTo(T)

現在のインスタンスを同じ型の別のオブジェクトと比較し、現在のインスタンスの並べ替え順序での位置が、比較対象のオブジェクトと比べて前か、後か、または同じかを示す整数を返します。Compares the current instance with another object of the same type and returns an integer that indicates whether the current instance precedes, follows, or occurs in the same position in the sort order as the other object.

適用対象

こちらもご覧ください