# 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>``
``type IComparable<'T> = interface``
``Public Interface IComparable(Of In T)``

T

## 例

``````#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(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");

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(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");

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(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")

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、実装する型でCompareTo(T)、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、または同じのいずれであるかを示す単一のメソッド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、や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.

CompareTo(T)メソッドの実装では、次のInt32表に示すように、3つの値のいずれかを持つ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.

[値]Value 説明Meaning
0 より小さい値Less than zero このオブジェクトは、並べ替え順序においCompareToて、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.
0Zero 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.
0 より大きい値Greater than zero この現在のインスタンスは、並べ替え順序にCompareToおいて、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String) はIComparable<T>、、、およびChar DateTimeのようにを実装します。All numeric types (such as Int32 and Double) implement IComparable<T>, as do String, Char, and DateTime. また、カスタム型では、オブジェクトインスタンスIComparable<T>の順序付けまたは並べ替えを有効にするために、の独自の実装も提供する必要があります。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.

を実装IComparable<T>する場合は`op_LessThan` `op_GreaterThanOrEqual` `op_GreaterThan`、、、、および`op_LessThanOrEqual`の各演算子をオーバーロードして、とCompareTo(T)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、も実装IEquatable<T>する必要があります。In addition, you should also implement IEquatable<T>. 詳細にIEquatable<T>ついては、「」を参照してください。See the IEquatable<T> article for complete information.

## メソッド

 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.