delphimvcframework/sources/MVCFramework.Nullables.pas.template

// ***************************************************************************
// 
// THIS FILE IS GENERATED BY "inv generate-nullables" DO NOT CHANGE MANUALLY!
// 
// ***************************************************************************
//
// *************************************************************************** }
//
// Delphi MVC Framework
//
// Copyright (c) 2010-2020 Daniele Teti and the DMVCFramework Team
//
// https://github.com/danieleteti/delphimvcframework
//
// ***************************************************************************
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.


unit MVCFramework.Nullables;

interface

uses
  System.SysUtils, System.Classes;

type
  EMVCNullable = class(Exception)

  end;

///INTERFACE.BEGIN
  Nullable$TYPE$ = record
  private
    fValue: $TYPE$;
    fHasValue: String;
    function GetHasValue: Boolean;
  public
    procedure CheckHasValue;
    function GetValue: $TYPE$;
    procedure SetValue(const Value: $TYPE$);
    class operator Implicit(const Value: $TYPE$): Nullable$TYPE$;
    class operator Implicit(const Value: Nullable$TYPE$): $TYPE$;
    property HasValue: Boolean read GetHasValue;
	///<summary>
	///Alias of `SetNull`
	///</summary>
    procedure Clear;
	///<summary>
	///Set the value to `null`
	///</summary>
    procedure SetNull;
	///<summary>
	///Returns the value stored or the default value for the type is the value is not set
	///</summary>	
    function ValueOrDefault: $TYPE$;
	/// <summary>
	/// Returns true is both item have the same value and that value is not null. 
	/// </summary>
	function Equals(const Value: Nullable$TYPE$): Boolean;
	///<summary>
	///Returns the value stored or raises exception if no value is stored
	///</summary>	
    property Value: $TYPE$ read GetValue write SetValue;
  end;

///INTERFACE.END

implementation

///IMPLEMENTATION.BEGIN

{ Nullable$TYPE$ }

procedure Nullable$TYPE$.CheckHasValue;
begin
  if not GetHasValue then
  begin
    raise EMVCNullable.Create('Value is null');
  end;
end;

procedure Nullable$TYPE$.Clear;
begin
  SetNull;
end;

function Nullable$TYPE$.Equals(const Value: Nullable$TYPE$): Boolean;
begin
  Result := (Self.HasValue and Value.HasValue) and (Self.Value = Value.Value);
end;

function Nullable$TYPE$.GetHasValue: Boolean;
begin
  Result := fHasValue = '_';
end;

function Nullable$TYPE$.GetValue: $TYPE$;
begin
  CheckHasValue;
  Result := fValue;
end;

class operator Nullable$TYPE$.Implicit(const Value: Nullable$TYPE$): $TYPE$;
begin
  Result := Value.Value;
end;

class operator Nullable$TYPE$.Implicit(const Value: $TYPE$): Nullable$TYPE$;
begin
  Result.Value := Value;
end;

procedure Nullable$TYPE$.SetNull;
begin
  fValue := Default ($TYPE$);
  fHasValue := '';
end;

procedure Nullable$TYPE$.SetValue(const Value: $TYPE$);
begin
  fValue := Value;
  fHasValue := '_';
end;

function Nullable$TYPE$.ValueOrDefault: $TYPE$;
begin
  if HasValue then
  begin
    Result := GetValue
  end
  else
  begin
    Result := Default ($TYPE$);
  end;
end;

///IMPLEMENTATION.END

end.