新创建的结构体的返回类型是什么?

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英文:

what is the return type of new-ed struct?

问题

例如,我有这个结构体:

type MapReduce struct {
    nMap            int    // Map 任务的数量
    nReduce         int    // Reduce 任务的数量
    file            string // 输入文件的名称
    MasterAddress   string
    registerChannel chan string
    DoneChannel     chan bool
    alive           bool
    l               net.Listener
    stats           *list.List

    // 需要保持更新的已注册工作节点的映射
    Workers map[string]*WorkerInfo

    // 在这里添加任何其他状态
}

然后我这样创建它:

mr := new(MapReduce)

然后我这样使用它:

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

我的问题是,rpc.Register 接受接口作为参数。http://golang.org/pkg/net/rpc/#Server
但是这里的 mr 不是接口,为什么这样是正确的?

谢谢

英文:

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

答案1

得分: 3

interface{} 是一个空接口类型,可以被任何类型满足。

因此,你可以将 *MapReduce 传递给 Register(interface{}) 方法。

根据接口类型规范

> 一个类型可以实现其方法的任何子集,因此可以实现多个不同的接口。
例如,所有类型都实现了空接口:

interface{}

但要记住,一旦传递后,它的静态类型变为 interface{}
反射定律提到:

> 有人说Go的接口是动态类型,但这是误导。
>
> 它们是静态类型的:接口类型的变量始终具有相同的静态类型,即使在运行时存储在接口变量中的值可能会更改类型,该值仍将满足接口。

更多信息请参见“在Go中interface{}的含义是什么?”。

英文:

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?".

huangapple
  • 本文由 发表于 2014年5月19日 00:14:03
  • 转载请务必保留本文链接:https://go.coder-hub.com/23724074.html
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