新结构的返回类型是什么？

Question

For example, I have this struct:

type MapReduce struct {
    nMap            int    // Number of Map jobs
    nReduce         int    // Number of Reduce jobs
    file            string // Name of input file
    MasterAddress   string
    registerChannel chan string
    DoneChannel     chan bool
    alive           bool
    l               net.Listener
    stats           *list.List

    // Map of registered workers that you need to keep up to date
    Workers map[string]*WorkerInfo

    // add any additional state here
}

Then I new it like this:

mr := new(MapReduce)

Then I use it like this:

rpcs := rpc.NewServer()
rpcs.Register(mr)

My question is ,, rpc.Register takes interface as argument. http://golang.org/pkg/net/rpc/#Server but mr here is not interface, why is it right?

Thanks

Answer 1

It does take an empty interface type interface{}, which is satisfied by any type.

So you can pass a *MapReduce to the Register(interface{}) method.

From spec interface type:

A type implements any interface comprising any subset of its methods and may therefore implement several distinct interfaces.
For instance, all types implement the empty interface:

interface{}

Bit remember, once it is passed, its static type become interface{}.
Law of reflection mentions:

Some people say that Go's interfaces are dynamically typed, but that is misleading.

They are statically typed: a variable of interface type always has the same static type, and even though at run time the value stored in the interface variable may change type, that value will always satisfy the interface.

See more at "what is the meaning of interface{} in golang?".