go - 如果不是隐式调用接口(interface)，如何访问函数？

Question

下面是一个结构Config，它包含一个匿名函数ReturnNewAddress，它返回一个net.Conn接口(interface)。 ReturnNewAddress 然后用于返回“地址”。

type struct Config { 

    ReturnNewAddress func(net.Conn, error) 

}

在下面调用匿名函数 ReturnnewAddress 的地方，请注意 cfg 是 Config 的一个实例。

addr, err := cfg.ReturnNewAddress()

所以我的问题来了 - 考虑到接口(interface)拥有许多不同的功能，接口(interface) net.Conn 如何知道要使用什么功能？让我感到困惑的是 LocalAddr() 或 RemoteAddr() 没有被隐式调用。如何明确使用这些方法之一。如果我需要显式使用 LocalAddr 而不是 RemoteAddr 怎么办？

下面是net.Conn的go doc:

type Conn interface {
    // Read reads data from the connection.
    // Read can be made to time out and return an Error with Timeout() == true
    // after a fixed time limit; see SetDeadline and SetReadDeadline.
    Read(b []byte) (n int, err error)

    // Write writes data to the connection.
    // Write can be made to time out and return an Error with Timeout() == true
    // after a fixed time limit; see SetDeadline and SetWriteDeadline.
    Write(b []byte) (n int, err error)

    // Close closes the connection.
    // Any blocked Read or Write operations will be unblocked and return errors.
    Close() error

    // LocalAddr returns the local network address.
    LocalAddr() Addr

    // RemoteAddr returns the remote network address.
    RemoteAddr() Addr

    // SetDeadline sets the read and write deadlines associated
    // with the connection. It is equivalent to calling both
    // SetReadDeadline and SetWriteDeadline.
    //
    // A deadline is an absolute time after which I/O operations
    // fail with a timeout (see type Error) instead of
    // blocking. The deadline applies to all future and pending
    // I/O, not just the immediately following call to Read or
    // Write. After a deadline has been exceeded, the connection
    // can be refreshed by setting a deadline in the future.
    //
    // An idle timeout can be implemented by repeatedly extending
    // the deadline after successful Read or Write calls.
    //
    // A zero value for t means I/O operations will not time out.
    SetDeadline(t time.Time) error

    // SetReadDeadline sets the deadline for future Read calls
    // and any currently-blocked Read call.
    // A zero value for t means Read will not time out.
    SetReadDeadline(t time.Time) error

    // SetWriteDeadline sets the deadline for future Write calls
    // and any currently-blocked Write call.
    // Even if write times out, it may return n > 0, indicating that
    // some of the data was successfully written.
    // A zero value for t means Write will not time out.
    SetWriteDeadline(t time.Time) error
}
    Conn is a generic stream-oriented network connection.

Answer 1

问题不是很清楚，但是..

看起来配置类型的代码有一个拼写错误

   ReturnNewAddress func(net.Conn, error) 

没有与后面的代码兼容的函数类型

addr, err := cfg.ReturnNewAddress()

我相信配置结构类型应该定义为

type struct Config { 
    ReturnNewAddress func()(net.Conn, error) 
}

基于此，调用 cfg.ReturnNewAddress() 返回的变量 addr 的类型为 net.Conn - 所以它是实现接口(interface) net.Conn 的值。因此，您可以按如下方式显式调用所需的函数:

localAddr  :=addr.LocalAddr();
remoteAddr := addr.RemoteAddr();