在kubernetes代码中，& deployment如何满足类型runtime.Object？ [英] How can &deployment satisfy type runtime.Object in kubernetes code?

问题描述

在 kubectl /在Kubernetes代码中运行.go ，生成函数有一个这两种类型的结果列表：

In kubectl/run.go in Kubernetes code, the Generate function has a result list of these two types:

runtime.Object, error

该函数的最后一行是：

return &deployment, nil

运行时已导入：

k8s.io/apimachinery/pkg/runtime

我有 runtime 在该import语句上运行 go get ，并在 interfaces.go <中定义Object / code>：

I got runtime by running go get on that import statement, and Object is defined in interfaces.go:

type Object interface {
    GetObjectKind() schema.ObjectKind
    DeepCopyObject() Object
}

（我在网上找到了相同的代码这里。）

(And I found the same code on the web here.)

地址运算符创建指针...更具体地说，Go规范说明：

The address operator creates a pointer... more specifically, the Go spec states:

对于类型为T的操作数x，地址操作& x生成类型为* T的指针x。

For an operand x of type T, the address operation &x generates a pointer of type *T to x.

和指针的类型与其基类型不同：

指针类型表示指向变量的所有指针的集合给定类型，称为指针的基本类型。

A pointer type denotes the set of all pointers to variables of a given type, called the base type of the pointer.

& deployment 满足 runtime.Object 类型？

到目前为止，我最好的猜测是 deployment 实现 runtime.Object 接口，并将& deployment 映射到 runtime.Object 满足这个可转让性规则：

My best guess so far is that deployment implements the runtime.Object interface, and mapping &deployment to runtime.Object satisfies this rule of assignability:

T是接口类型，x实现T.

T is an interface type and x implements T.

并且映射到结果列表类型的return语句等效于此方面的赋值。它是否正确？如果没有，是否有其他部分说明或文档解释它？

and that a return statement statement mapping to a result list type is equivalent to assignment in this respect. Is this correct? If not, is there another part of the specification or documentation that explains it?

推荐答案

部署是一个局部变量，它的声明：

deployment is a local variable, its declaration:

deployment := extensionsv1beta1.Deployment{
    // ...
}

其中 extensionsv1beta1 来自进口：

import (
    // ...
    extensionsv1beta1 "k8s.io/api/extensions/v1beta1"
    // ...
)

extensionsv1beta1.Deployment 的文件。它的定义是：

Doc of extensionsv1beta1.Deployment. Its definition is:

type Deployment struct {
    metav1.TypeMeta `json:",inline"`
    // ...other fields...
}

嵌入 metav1.TypeMeta ，它有一个方法 带指针接收器的GetObjectKind（） 方法。这意味着指向部署的指针也有此方法，因为规范：结构类型：

It embeds metav1.TypeMeta, which has a method GetObjectKind() method with pointer receiver. This means a pointer to Deployment also has this method, because Spec: Struct types:

给定结构类型 S 和定义的类型 T ，提升的方法包含在结构的方法集中，如下所示：

Given a struct type S and a defined type T, promoted methods are included in the method set of the struct as follows:

• 如果 S 包含嵌入字段 T ，则方法集 S 和 * S 都包含提升方法，接收方 T 。 * S 的方法集还包括带接收方 * T 的推广方法。

• If S contains an embedded field T, the method sets of S and *S both include promoted methods with receiver T. The method set of *S also includes promoted methods with receiver *T.

和部署有直接< A HREF = https://godoc.org/k8s.io/api/extensions/v1beta1#Deployment.DeepCopyObject 相对= nofollow noreferrer> DeepCopyObject（） 方法，再次使用指针接收器。所以方法集 *部署包含此方法。

And Deployment has a "direct" DeepCopyObject() method, again with pointer receiver. So the method set of *Deployment contains this method.

最后引用规范：接口类型：

接口类型指定方法集称为 interface 。 接口类型的变量可以存储任何类型的值，其方法集是接口的任何超集。这样的类型被称为实现接口。

An interface type specifies a method set called its interface. A variable of interface type can store a value of any type with a method set that is any superset of the interface. Such a type is said to implement the interface.

所以这意味着 * Deployment 的方法集具有 Object ，或换句话说： * Deployment 的方法集是<$ c $方法集的超集c>对象，所以 *部署实现对象。

So this means the method set of *Deployment has all the methods defined by Object, or in other words: the method set of *Deployment is a superset of the method set of Object, so *Deployment implements Object.

部署的类型为 extensionsv1beta1.Deployment ，这意味着 & deployment 的类型为 * extensionsv1beta1.Deployment ，我们在上面显示它实现了 Object ;所以可以将值& deployment 分配给或存储在 Object 类型的变量中。

deployment is of type extensionsv1beta1.Deployment, which means &deployment is of type *extensionsv1beta1.Deployment, which we showed above that it implements Object; so the value &deployment can be assigned to or be stored in a variable of type Object.

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