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DefaultImplementation Property

  • Άρθρο

Version: Available or changed with runtime version 5.0.

Specifies the default implementer for the enum value if there is no explicit implementer set for the value.

Applies to

  • Enum Type

Syntax

DefaultImplementation = Interface = InterfaceImplementation;

Example

The following example illustrates different implementations of the IFoo interface. SomeEnum has DefaultImplementation set to catch the case where some extension uses an enum value that does not implement the IFoo interface.

pageextension 50130 CustListExt extends "Customer List"
{

    trigger OnOpenPage()
    var
        ifoo: Interface IFoo;
        e: enum SomeEnum;
    begin
        e := SomeEnum::Yes;
        ifoo := e;
        ifoo.Foo(); // => YesFooImpl specified in Implementation on Yes value

        e := SomeEnum::No;
        ifoo := e;
        ifoo.Foo(); // => DefaultFooImpl specified in DefaultImplementation

        e := 2; // No enum value matches this.
        ifoo := e;
        ifoo.Foo(); // => UnknownFooImpl specified in UnknownImplementation
    end;
}

interface IFoo
{
    procedure Foo()
}

codeunit 50145 ErrorFooImpl implements IFoo
{
    procedure Foo()
    begin
        Message('Bad FOO')
    end;
}

codeunit 50146 DefaultFooImpl implements IFoo
{
    procedure Foo()
    begin
        Message('Default FOO')
    end;
}

codeunit 50147 YesFooImpl implements IFoo
{
    procedure Foo()
    begin
        Message('Yes FOO')
    end;
}

enum 50135 SomeEnum implements IFoo
{
    Extensible = true;
    UnknownValueImplementation = IFoo = ErrorFooImpl;
    DefaultImplementation = IFoo = DefaultFooImpl;

    value(0; Yes)
    {
        Implementation = IFoo = YesFooImpl;
    }
    value(1; No)
    {
        // Nothing specified. Using defaults
    }
}

Remarks

Adding a new interface to an existing, extensible enum, requires that all extensions of that enum provide an implementations for the interface, which is a breaking change. Providing a default implementation by using the DefaultImplementation property can be used to make such new additions non-breaking.

Related to DefaultImplementation is the UnknownValueImplementation property, used for handling unknown enum values. For more information, see UnknownValueImplementation Property.

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