{"id":4509,"date":"2023-05-16T10:27:41","date_gmt":"2023-05-16T09:27:41","guid":{"rendered":"https:\/\/gdksoftware.com\/knowledgebase\/spring4d-factory-pattern"},"modified":"2023-05-16T18:44:36","modified_gmt":"2023-05-16T17:44:36","slug":"spring4d-factory-pattern","status":"publish","type":"knowledge","link":"https:\/\/gdksoftware.com\/pt-br\/base-de-conhecimento\/spring4d-factory-pattern","title":{"rendered":"Spring4D factory pattern"},"content":{"rendered":"
\n

Que op\u00e7\u00f5es existem na estrutura do Spring4D<\/strong> que n\u00e3o conhecemos, mas que s\u00e3o muito \u00fateis<\/strong>? Bem, na verdade, s\u00e3o muitos. Um deles \u00e9 o Factory Pattern<\/strong>. Ele \u00e9 muito \u00fatil quando voc\u00ea deseja aplicar o padr\u00e3o\u00a0open\/closed principle<\/a>. Seu c\u00f3digo est\u00e1 aberto para extens\u00e3o, mas fechado para modifica\u00e7\u00e3o.<\/p>\n

Um exemplo cl\u00e1ssico \u00e9 trabalhar com enumera\u00e7\u00f5es ou n\u00fameros que indicam um determinado estado. Isso cria rapidamente todos os tipos de estruturas condicionais que precisam ser adaptadas assim que um novo status ou valor \u00e9 adicionado. No exemplo abaixo, determinado c\u00f3digo \u00e9 executado dependendo do status de uma fatura. Para dividir o c\u00f3digo, foi aplicado o Factory pattern.<\/p>\n

Essa \u00e9 a defini\u00e7\u00e3o de Invoice e status:<\/p>\n<\/div>\n

\n
type<\/span>\r\n  {$SCOPEDENUMS ON}<\/span>\r\n  TInvoiceStatus = (New<\/span>, Sent, Overdue, Paid);\r\n  {$SCOPEDENUMS OFF}<\/span>\r\n\r\n  TInvoice = class<\/span>\r\n  public<\/span>\r\n    function<\/span> Status: TInvoiceStatus;\r\n  end<\/span>;\r\n<\/pre>\n<\/div>\n
Para usar o Factory pattern, inclu\u00edmos a unidade Spring.DesignPatterns<\/strong>. Em seguida, definimos a Factory pattern. Ela consiste em um valor-chave e uma fun\u00e7\u00e3o que retorna o m\u00e9todo que voc\u00ea deseja executar. Isso parece complexo, mas n\u00e3o \u00e9 t\u00e3o ruim. Em nosso caso, o valor-chave \u00e9 o status do Invoice (TInvoiceStatus). A fun\u00e7\u00e3o que queremos executar tem o Invoice (TInvoice) como par\u00e2metro. A defini\u00e7\u00e3o da Factory pattern fica assim:<\/div>\n
\n
type<\/span>\r\n  TProcessInvoiceProc = reference to<\/span> procedure<\/span>(const<\/span> Invoice: TInvoice);\r\n\r\n  TInvoiceProcessor = class<\/span>\r\n  private<\/span>\r\n    FFactory: TFactory<TInvoiceStatus, TProcessInvoiceProc >;\r\n    procedure<\/span> InitialiseFactory;\r\n  end<\/span>;\r\n\r\nprocedure<\/span> TInvoiceProcessor .InitialiseFactory;\r\nbegin<\/span>\r\n  FFactory := TFactory<TInvoiceStatus, TProcessInvoiceProc >.Create;\r\n\r\n  FFactory.RegisterFactoryMethod(TInvoiceStatus.New<\/span>, ProcessInvoiceNew);\r\n  FFactory.RegisterFactoryMethod(TInvoiceStatus.Sent, ProcessInvoiceSent);\r\n  FFactory.RegisterFactoryMethod(TInvoiceStatus.Overdue, ProcessInvoiceOverdue);\r\n  FFactory.RegisterFactoryMethod(TInvoiceStatus.Paid, ProcessInvoicePaid);\r\nend<\/span>;\r\n<\/pre>\n<\/div>\n
O c\u00f3digo acima j\u00e1 mostra como o Factory pattern \u00e9 criada e inicializada. Associada a cada status est\u00e1 uma fun\u00e7\u00e3o “Process”. Essa fun\u00e7\u00e3o retorna a defini\u00e7\u00e3o do TProcessInvoiceProc para executar o c\u00f3digo para esse status. Voc\u00ea define isso da seguinte forma:<\/div>\n
\n
function<\/span> TInvoiceProcessor .ProcessInvoiceNew: TProcessInvoiceProc;\r\nbegin<\/span>\r\n  Result := procedure<\/span>(const<\/span> Invoice: TInvoice)\r\n            begin<\/span>\r\n              ShowMessage('This is a new invoice'<\/span>);\r\n            end<\/span>\r\nend<\/span>;\r\n<\/pre>\n<\/div>\n
\n
A aplica\u00e7\u00e3o do Factory pattern \u00e9 f\u00e1cil e ocorre conforme o c\u00f3digo abaixo:<\/p>\n<\/div>\n
\n
procedure<\/span> TInvoiceProcessor .ProcessInvoice(const<\/span> Invoice: TInvoice);\r\nbegin<\/span>\r\n  if<\/span> FFactory.IsRegistered(Invoice.Status) then<\/span>\r\n  begin<\/span>\r\n    var<\/span> Process := FFactory.GetInstance(Invoice.Status;)\r\n    Process(Invoice);\r\n  end<\/span>;\r\nend<\/span>;\r\n<\/pre>\n<\/div>\n
Dessa forma, usando o Factory pattern, seu c\u00f3digo \u00e9 f\u00e1cil de dividir e melhorar.<\/div>\n","protected":false},"featured_media":0,"parent":0,"template":"","class_list":["post-4509","knowledge","type-knowledge","status-publish","hentry","knowledge-category-arquivo-delphi"],"acf":{"author":413,"type_hero":"compact","hero_image":4500,"hero_image_position":"","hero_title":"Spring4D factory pattern","hero_content":"","hero_link":null,"hero_show_h1":false},"yoast_head":"\nSpring4D factory pattern - GDK Software<\/title>\n<meta name=\"description\" content=\"Que op\u00e7\u00f5es existem na estrutura do Spring4D que n\u00e3o conhecemos, mas que s\u00e3o muito \u00fateis? 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