c# - Unity IOC 使用InjectionConstructor 简化类型注册

Question

我想使用注入(inject)构造函数简化类型注册。 IOC 通常应该自行解析类型。有些类型不能自动解析，因为它们的构造函数需要一些命名参数。他们需要自定义注册。

例如:

public DatabaseLayer(string connectionString, 
                     string userName,
                     ILogger loger, 
                     TypeMapper mapper,
                     ...some other dependencies)

类型注册:

container.RegisterType<DatabaseLayer>(
    new InjectionConstructor(
        new ResolvedParameter<string>("connectionString"),
        new ResolvedParameter<string>("userName"),
        new ResolvedParameter<ILoger>("file")
        typeof(TypeMapper),
        typeof(..),
        ...));

如您所见，如果您在注册中需要任何命名解析，则需要记下数十个未命名参数或应用程序在运行时崩溃。更糟糕的是，每次更改构造函数参数时都需要更正注册。在 Programm 在运行时崩溃之前，您不会注意到任何事情。

所以我正在寻找扩展或配置 Unity 的方法，它允许我跳过默认(无名)参数注册以减少可能的错误并使 Bootstrap 尽可能小。

编辑很好地找到了我正在寻找的东西。 https://outlawtrail.wordpress.com/2012/08/02/fun-with-constructor-arguments-part-1-pick-choose/

智能构造函数似乎是解决方案

Answer 1

一种选择是使用 InjectionFactory 而不是 InjectionConstructor。

假设这个模型:

public class DataBaseLayer
{
    private readonly string _connectionString;
    private readonly string _userName;
    private readonly ILogger _logger;
    private readonly ITypeMapper _mapper;

    public DataBaseLayer(
        string connectionString,
        string userName,
        ILogger logger,
        ITypeMapper mapper)
    {
        _connectionString = connectionString;
        _userName = userName;
        _logger = logger;
        _mapper = mapper;
    }
}

public interface ITypeMapper
{
}

public class TypeMapper : ITypeMapper
{
}

public interface ILogger
{

}

public class Logger : ILogger
{

}

假设 Username 和 ConnectionString 存储在配置文件中(您没有指定这些参数的来源)，我将创建一个 Bootstrapper 类如下所示:

public static class Bootstrapper
{
    // assuming Username is a configuration setting stored in the config file
    private static string Username => ConfigurationManager.AppSettings["username"];

    // assuming ConnectionString is a connection string stored in the config file
    private static string ConnectionString => ConfigurationManager.ConnectionStrings["myConnectionString"].ConnectionString;

    public static IUnityContainer Setup()
    {
        IUnityContainer container = new UnityContainer();
        container.RegisterType<ILogger, Logger>();
        container.RegisterType<ITypeMapper, TypeMapper>();
        container.RegisterType<DataBaseLayer>(new InjectionFactory(CreateDataBaseLayer));

        return container;
    }

    private static DataBaseLayer CreateDataBaseLayer(IUnityContainer container)
    {
        ILogger logger = container.Resolve<ILogger>();
        ITypeMapper mapper = container.Resolve<ITypeMapper>();

        return new DataBaseLayer(ConnectionString, Username, logger, mapper);
    }
}

使用代码:

IUnityContainer container = Bootstrapper.Setup();
DataBaseLayer dbLayer = container.Resolve<DataBaseLayer>();