忽略这个使用Aurelius框架的事实,这个问题更多的是关于如何重新调整代码以使这两种类型的泛型构造函数注入都可以工作:
<字符串>
和
< TCustomConnection>
还忽略了一个事实,孩子的对象是在同一个单位,我一般把他们自己,但这恰恰使得它更容易在发帖提问。什么是构造这个通用对象创建的正确方法
我想使用工厂方法模式来确定它应该在运行时进行什么类型的连接,具体取决于我实例化的对象。 目前,它正在对创建期望的链接类型进行硬编码。
在这个例子中,我想传递一个TModelDatabaseLink,但想要在运行时决定它可能是什么类型的数据库连接,或者数据库连接是否来自一个文件。 是的,我知道我可以取消注释FFilename,只是用它来保存文件名版本,但我总是有兴趣学习更多。我想如果可能的话做,
unit Model.Database.Connection;
interface
uses
System.Classes,
Data.DB,
Aurelius.Drivers.Interfaces,
Aurelius.Engine.DatabaseManager;
type
TModelDatabaseLink<T> = class
private
//FFilename: string;
FConnection: T;
FOwnsConnection: boolean;
OwnedComponent: TComponent;
end;
TModelDatabaseConnection = class abstract
private
FDatabaseLink: TModelDatabaseLink<TCustomConnection>;
FDatabaseManager: TDatabaseManager;
FConnection: IDBConnection;
function CreateConnection: IDBConnection; virtual; abstract;
procedure CreateDatabaseManager;
public
constructor Create(ADatabaseLink: TModelDatabaseLink<TCustomConnection>);
destructor Destroy; override;
property Connection: IDBConnection read FConnection;
end;
TSQLLiteConnection = class(TModelDatabaseConnection)
private
function CreateConnection: IDBConnection; override;
end;
TFireDacConnection = class(TModelDatabaseConnection)
private
function CreateConnection: IDBConnection; override;
end;
implementation
uses
System.SysUtils,
Aurelius.Drivers.Base,
Aurelius.Drivers.SQLite,
Aurelius.Drivers.FireDac,
FireDAC.Stan.Intf, FireDAC.Stan.Option,
FireDAC.Stan.Error, FireDAC.UI.Intf, FireDAC.Phys.Intf, FireDAC.Stan.Def,
FireDAC.Stan.Pool, FireDAC.Stan.Async, FireDAC.Phys, FireDAC.VCLUI.Wait,
FireDAC.Comp.Client;
{ TModelDatabaseConnection }
constructor TModelDatabaseConnection.Create(ADatabaseLink: TModelDatabaseLink<TCustomConnection>);
begin
FDatabaseLink := ADatabaseLink;
FConnection := CreateConnection;
if Assigned(FConnection) then
CreateDatabaseManager
else
raise Exception.Create('Failed to open database');
end;
procedure TModelDatabaseConnection.CreateDatabaseManager;
begin
FDatabaseManager := TDatabaseManager.Create(FConnection);
end;
destructor TModelDatabaseConnection.Destroy;
begin
FDatabaseManager.Free;
FDatabaseLink.Free;
inherited Destroy;
end;
{ TSQLLiteConnection }
function TSQLLiteConnection.CreateConnection: IDBConnection;
var
LFilename: String;
LAdapter: TSQLiteNativeConnectionAdapter;
begin
//LFileName := FDatabaseLink.FConnection; << needs to be type string
LAdapter := TSQLiteNativeConnectionAdapter.Create(LFilename);
LAdapter.DisableForeignKeys;
Result := LAdapter;
end;
{ TFireDacConnection }
function TFireDacConnection.CreateConnection: IDBConnection;
var
LAdapter: TFireDacConnectionAdapter;
begin
if Assigned(FDatabaseLink.OwnedComponent) then
LAdapter := TFireDacConnectionAdapter.Create(FDatabaseLink.FConnection as TFDConnection, FDatabaseLink.OwnedComponent)
else
LAdapter := TFireDacConnectionAdapter.Create(FDatabaseLink.FConnection as TFDConnection, FDatabaseLink.FOwnsConnection);
Result := LAdapter;
end;
end.
的另一件事就是修改两处作品:
LAdapter := TSQLiteNativeConnectionAdapter.Create(LFilename)
LAdapter := TFireDacConnectionAdapter.Create(FDatabaseLink.FConnection as TFDConnection, FDatabaseLink.OwnedComponent)
在父TModelDatabaseConnection使用抽象“GetAdapterClass”类型的功能,只是声明类的适配器的孩子做这样的事情:
LAdapter := GetAdapterClass.Create...
适配器声明的一个例子是
TFireDacConnectionAdapter = class(TDriverConnectionAdapter<TFDConnection>, IDBConnection)
难道你正在使用Spring.Persistence适配器吗?因为这段代码对我来说看起来很熟悉。如果是这样,请查看Spring.Persistence.Core.ConnectionFactory.pas注入适配连接的不同ctor参数的方式。 –
嘿Stefan。实际上,这些实际上是TMS Aurelius框架中的那些。不过,我会看看Spring的单元,就像我在PC上看到的那样,看看它是否给了我更多的线索。 – mikelittlewood
嗨Stefan。在Spring.Persistence.Adapters.SQLite中,您指定必须传递TSQLiteDatabase而不仅仅是文件名。在Spring代码中唯一可以找到的是.. \ Marshmallow \ External \ SQLite3。这是一个“官方”春季吗? – mikelittlewood