Action<T1,T2,T3> Delegat

Definicja

generic <typename T1, typename T2, typename T3>
public delegate void Action(T1 arg1, T2 arg2, T3 arg3);

public delegate void Action<in T1,in T2,in T3>(T1 arg1, T2 arg2, T3 arg3);

public delegate void Action<T1,T2,T3>(T1 arg1, T2 arg2, T3 arg3);

type Action<'T1, 'T2, 'T3> = delegate of 'T1 * 'T2 * 'T3 -> unit

Public Delegate Sub Action(Of In T1, In T2, In T3)(arg1 As T1, arg2 As T2, arg3 As T3)

Public Delegate Sub Action(Of T1, T2, T3)(arg1 As T1, arg2 As T2, arg3 As T3)

Parametry typu

Parametry

Uwagi

Możesz użyć delegata Action<T1,T2,T3>, aby przekazać metodę jako parametr bez jawnego deklarowania delegata niestandardowego. Hermetyzowana metoda musi odpowiadać sygnaturze metody zdefiniowanej przez ten delegat. Oznacza to, że metoda hermetyzowana musi mieć trzy parametry, które są przekazywane do niej według wartości, i nie może zwracać wartości. (W języku C#metoda musi zwrócić void. W języku F# metoda lub funkcja musi zwracać jednostkę. W języku Visual Basic musi być zdefiniowany przez konstrukcję Sub...End Sub. Może to być również metoda zwracająca wartość, która jest ignorowana. Zazwyczaj taka metoda służy do wykonywania operacji.

Jeśli używasz delegata Action<T1,T2,T3>, nie musisz jawnie definiować delegata, który hermetyzuje metodę z trzema parametrami. Na przykład poniższy kod jawnie deklaruje delegata o nazwie StringCopy i przypisuje odwołanie do metody CopyStrings do wystąpienia delegata.

using System;

delegate void StringCopy(string[] stringArray1,
                         string[] stringArray2,
                         int indexToStart);

public class TestDelegate
{
    public static void Main()
    {
        string[] ordinals = ["First", "Second", "Third", "Fourth", "Fifth"];
        string[] copiedOrdinals = new string[ordinals.Length];
        StringCopy copyOperation = CopyStrings;
        copyOperation(ordinals, copiedOrdinals, 3);
        foreach (string ordinal in copiedOrdinals)
            Console.WriteLine(string.IsNullOrEmpty(ordinal) ? "<None>" : ordinal);
    }

    private static void CopyStrings(string[] source, string[] target, int startPos)
    {
        if (source.Length != target.Length)
            throw new IndexOutOfRangeException("The source and target arrays must have the same number of elements.");

        for (int ctr = startPos; ctr <= source.Length - 1; ctr++)
            target[ctr] = source[ctr];
    }
}

open System

type StringCopy = delegate of stringArray1: string [] * 
                              stringArray2: string [] * 
                              indexToStart: int -> unit

let copyStrings (source: string []) (target: string []) startPos =
    if source.Length <> target.Length then
        raise (IndexOutOfRangeException "The source and target arrays must have the same number of elements.")

    for i = startPos to source.Length - 1 do
        target.[i] <- source.[i]

let ordinals = [| "First"; "Second"; "Third"; "Fourth"; "Fifth" |]
let copiedOrdinals: string [] = Array.zeroCreate ordinals.Length

let copyOperation = StringCopy copyStrings

copyOperation.Invoke(ordinals, copiedOrdinals, 3)

for ordinal in copiedOrdinals do
    printfn "%s" (if String.IsNullOrEmpty ordinal then "<None>" else ordinal)

Delegate Sub StringCopy(stringArray1() As String,
                        stringArray2() As String,
                        indexToStart As Integer)

Module TestDelegate
    Public Sub RunIt()
        Dim ordinals() As String = {"First", "Second", "Third", "Fourth", "Fifth"}
        Dim copiedOrdinals(ordinals.Length - 1) As String
        Dim copyOperation As StringCopy = AddressOf CopyStrings
        copyOperation(ordinals, copiedOrdinals, 3)
        For Each ordinal As String In copiedOrdinals
            If String.IsNullOrEmpty(ordinal) Then
                Console.WriteLine("<None>")
            Else
                Console.WriteLine(ordinal)
            End If
        Next
    End Sub

    Private Sub CopyStrings(source() As String, target() As String, startPos As Integer)
        If source.Length <> target.Length Then
            Throw New IndexOutOfRangeException("The source and target arrays must have the same number of elements.")
        End If
        For ctr As Integer = startPos To source.Length - 1
            target(ctr) = source(ctr)
        Next
    End Sub
End Module

Poniższy przykład upraszcza ten kod, tworząc wystąpienie delegata Action<T1,T2,T3> zamiast jawnie definiować nowego delegata i przypisywać do niego nazwaną metodę.

using System;

public class TestAction3
{
    public static void Main()
    {
        string[] ordinals = ["First", "Second", "Third", "Fourth", "Fifth"];
        string[] copiedOrdinals = new string[ordinals.Length];
        Action<string[], string[], int> copyOperation = CopyStrings;
        copyOperation(ordinals, copiedOrdinals, 3);
        foreach (string ordinal in copiedOrdinals)
            Console.WriteLine(string.IsNullOrEmpty(ordinal) ? "<None>" : ordinal);
    }

    private static void CopyStrings(string[] source, string[] target, int startPos)
    {
        if (source.Length != target.Length)
            throw new IndexOutOfRangeException("The source and target arrays must have the same number of elements.");

        for (int ctr = startPos; ctr <= source.Length - 1; ctr++)
            target[ctr] = source[ctr];
    }
}

open System

let copyStrings (source: string []) (target: string []) startPos =
    if source.Length <> target.Length then
        raise (IndexOutOfRangeException "The source and target arrays must have the same number of elements.")

    for i = startPos to source.Length - 1 do
        target.[i] <- source.[i]

let ordinals = [| "First"; "Second"; "Third"; "Fourth"; "Fifth" |]
let copiedOrdinals = Array.zeroCreate<string> ordinals.Length

let copyOperation = Action<_,_,_> copyStrings

copyOperation.Invoke(ordinals, copiedOrdinals, 3)

for ordinal in copiedOrdinals do
    printfn "%s" (if String.IsNullOrEmpty ordinal then "<None>" else ordinal)

Module TestAction3
    Public Sub RunIt()
        Dim ordinals() As String = {"First", "Second", "Third", "Fourth", "Fifth"}
        Dim copiedOrdinals(ordinals.Length - 1) As String
        Dim copyOperation As Action(Of String(), String(), Integer) = AddressOf CopyStrings
        copyOperation(ordinals, copiedOrdinals, 3)
        For Each ordinal As String In copiedOrdinals
            If String.IsNullOrEmpty(ordinal) Then
                Console.WriteLine("<None>")
            Else
                Console.WriteLine(ordinal)
            End If
        Next
    End Sub

    Private Sub CopyStrings(source() As String, target() As String, startPos As Integer)
        If source.Length <> target.Length Then
            Throw New IndexOutOfRangeException("The source and target arrays must have the same number of elements.")
        End If
        For ctr As Integer = startPos To source.Length - 1
            target(ctr) = source(ctr)
        Next
    End Sub
End Module

Możesz również użyć delegata Action<T1,T2,T3> z metodami anonimowymi w języku C#, jak pokazano w poniższym przykładzie. (Aby zapoznać się z wprowadzeniem do metod anonimowych, zobacz Metody anonimowe).)

using System;

public class TestAnon
{
    public static void Main()
    {
        string[] ordinals = ["First", "Second", "Third", "Fourth", "Fifth"];
        string[] copiedOrdinals = new string[ordinals.Length];
        Action<string[], string[], int> copyOperation = delegate (string[] s1,
                                                                 string[] s2,
                                                                 int pos)
                                        { CopyStrings(s1, s2, pos); };
        copyOperation(ordinals, copiedOrdinals, 3);
        foreach (string ordinal in copiedOrdinals)
            Console.WriteLine(string.IsNullOrEmpty(ordinal) ? "<None>" : ordinal);
    }

    private static void CopyStrings(string[] source, string[] target, int startPos)
    {
        if (source.Length != target.Length)
            throw new IndexOutOfRangeException("The source and target arrays must have the same number of elements.");

        for (int ctr = startPos; ctr <= source.Length - 1; ctr++)
            target[ctr] = source[ctr];
    }
}

Można również przypisać wyrażenie lambda do wystąpienia delegata Action<T1,T2,T3>, jak pokazano w poniższym przykładzie. (Aby zapoznać się z wprowadzeniem do wyrażeń lambda, zobacz wyrażenia lambda (C#) lub wyrażenia lambda (F#).)

using System;

public class TestLambda
{
    public static void Main()
    {
        string[] ordinals = ["First", "Second", "Third", "Fourth", "Fifth"];
        string[] copiedOrdinals = new string[ordinals.Length];
        Action<string[], string[], int> copyOperation = (s1, s2, pos) =>
                                        CopyStrings(s1, s2, pos);
        copyOperation(ordinals, copiedOrdinals, 3);
        foreach (string ordinal in copiedOrdinals)
            Console.WriteLine(string.IsNullOrEmpty(ordinal) ? "<None>" : ordinal);
    }

    private static void CopyStrings(string[] source, string[] target, int startPos)
    {
        if (source.Length != target.Length)
            throw new IndexOutOfRangeException("The source and target arrays must have the same number of elements.");

        for (int ctr = startPos; ctr <= source.Length - 1; ctr++)
            target[ctr] = source[ctr];
    }
}

open System

let copyStrings (source: string []) (target: string []) startPos =
    if source.Length <> target.Length then
        raise (IndexOutOfRangeException "The source and target arrays must have the same number of elements.")

    for i = startPos to source.Length - 1 do
        target.[i] <- source.[i]

let ordinals = [| "First"; "Second"; "Third"; "Fourth"; "Fifth" |]
let copiedOrdinals: string [] = Array.zeroCreate ordinals.Length

let copyOperation = Action<_,_,_> (fun s1 s2 pos -> copyStrings s1 s2 pos)

copyOperation.Invoke(ordinals, copiedOrdinals, 3)

for ordinal in copiedOrdinals do
    printfn "%s" (if String.IsNullOrEmpty ordinal then "<None>" else ordinal)

Public Module TestLambda
    Public Sub RunIt()
        Dim ordinals() As String = {"First", "Second", "Third", "Fourth", "Fifth"}
        Dim copiedOrdinals(ordinals.Length - 1) As String
        Dim copyOperation As Action(Of String(), String(), Integer) =
                           Sub(s1, s2, pos) CopyStrings(s1, s2, pos)
        copyOperation(ordinals, copiedOrdinals, 3)
        For Each ordinal As String In copiedOrdinals
            If String.IsNullOrEmpty(ordinal) Then
                Console.WriteLine("<None>")
            Else
                Console.WriteLine(ordinal)
            End If
        Next
    End Sub

    Private Function CopyStrings(source() As String, target() As String, startPos As Integer) As Integer
        If source.Length <> target.Length Then
            Throw New IndexOutOfRangeException("The source and target arrays must have the same number of elements.")
        End If

        For ctr As Integer = startPos To source.Length - 1
            target(ctr) = source(ctr)
        Next
        Return source.Length - startPos
    End Function
End Module

' The example displays the following output:
'       Fourth
'       Fifth

Metody rozszerzania

Dotyczy

Zobacz też

• Func<T1,T2,T3,TResult>