Document type fazendo uso do factory

main.dart

enum DocumentStatus {
  pending,
  approved,
  rejected
}

class Document {
    String title;
    String content;
    DocumentStatus status;

    Document(this.title, this.content, [this.status = DocumentStatus.pending]);

    factory Document.pending(Document document) {
        return Document(document.title, document.content, DocumentStatus.pending);
    }

    factory Document.approved(Document document) {
        return Document(document.title, document.content, DocumentStatus.approved);
    }

    factory Document.rejected(Document document) {
        return Document(document.title, document.content, DocumentStatus.rejected);
    }
}

// FAZENDO O USO DO FACTORY
void main() {
    final document = Document('title', 'content');
    print(document.status); // DocumentStatus.pending

    final approvedDocument = Document.approved(document);
    print(approvedDocument.status); // DocumentStatus.approved
 
    final rejectedDocument = Document.rejected(document);
    print(rejectedDocument.status); // DocumentStatus.rejected

    final pendingDocument = Document.pending(document);
    print(pendingDocument.status); // DocumentStatus.pending
}