Question

我正在尝试子类化Connection对象以创建AuthenticatedConnection，它应该以与Connection相同的方式运行，并添加一个令牌。一个简单的解决方案是使用子类构造函数传递'wrap'连接。

此解决方案似乎已损坏，因为我无法访问参数的受保护成员。这意味着无法调用基础构造函数。有没有办法实现构造函数，以便可以像这样包装构造函数？例如：new AuthenticatedConnection("token", existingConnection)

这是当前（破碎）的实现。编译错误是：Cannot access protected member 'Connection._client' via a qualifier of type 'Connection'; the qualifier must be of type 'AuthenticatedConnection' (or derived from it)

class Connection
{
    // internal details of the connection; should not be public.
    protected object _client;

    // base class constructor
    public Connection(object client) { _client = client; }
}

class AuthenticatedConnection : Connection
{
    // broken constructor?
    public AuthenticatedConnection(string token, Connection connection)
        : base(connection._client)
    {
        // use token etc
    }
}

Answer 1

最简单的解决方案是为基类创建一个“复制构造函数”：

class Connection
{
    // internal details of the connection; should not be public.
    protected object _client;

    // base class constructor
    public Connection(object client) { _client = client; }

    // copying constructor
    public Connection(Connection other) : this(other._client) { }
}

class AuthenticatedConnection : Connection
{
    // broken constructor?
    public AuthenticatedConnection(string token, Connection connection)
        : base(connection)
    {
        // use token etc
    }
}

Answer 2

一个简单的解决方案是使用子类构造函数
传递'wrap'连接

这不是直截了当的，IMO。直截了当的是：

class AuthenticatedConnection : Connection
{
    public AuthenticatedConnection1(string token, object client)
        : base(client)
    {
        // use token etc
    }
}

但是如果你想包装真正的连接，我会这样做：

interface IConnection {}
class Connection : IConnection
{
    // internal details of the connection; should not be public.
    protected object _client;

    // base class constructor
    public Connection(object client) { _client = client; }
}

class AuthenticatedConnection : IConnection
{
    private readonly IConnection connection;

    public AuthenticatedConnection2(string token, IConnection connection)
    {
        // use token etc
    }
}

复制子类构造函数中的受保护字段

2 个答案: