Go实现枚举值

Go语言并没有提供enum的定义，我们可以使用const来模拟枚举类型，这也是Go语言中约定俗成的方式。

例如，在Kubernetes项目中，有大量的常量定义：

  1. // PodPhase is a label for the condition of a pod at the current time.
  2. type PodPhase string
  4. // These are the valid statuses of pods.
  5. const (
  6.     // PodPending means the pod has been accepted by the system, but one or more of the containers
  7.     // has not been started. This includes time before being bound to a node, as well as time spent
  8.     // pulling images onto the host.
  9.     PodPending PodPhase = "Pending"
  10.     // PodRunning means the pod has been bound to a node and all of the containers have been started.
  11.     // At least one container is still running or is in the process of being restarted.
  12.     PodRunning PodPhase = "Running"
  13.     // PodSucceeded means that all containers in the pod have voluntarily terminated
  14.     // with a container exit code of 0, and the system is not going to restart any of these containers.
  15.     PodSucceeded PodPhase = "Succeeded"
  16.     // PodFailed means that all containers in the pod have terminated, and at least one container has
  17.     // terminated in a failure (exited with a non-zero exit code or was stopped by the system).
  18.     PodFailed PodPhase = "Failed"
  19.     // PodUnknown means that for some reason the state of the pod could not be obtained, typically due
  20.     // to an error in communicating with the host of the pod.
  21.     PodUnknown PodPhase = "Unknown"
  22. )

如何跨服务高效维护枚举值

如果只是项目内部使用枚举值比较简单，定义完了内部使用即可，但涉及到跨服务之间调用，或者前后端协作时，效率就比较低了。当服务需要给外部调用者展示接口能力时，往往需要生成API接口文档（或者接口定义文件，例如proto），往往也需要根据接口文档（文件）生成调用的客户端SDK。

如果是接口定义文件，例如proto，往往可以直接查看源码来解决这个问题，问题不大。我们这里主要讨论的是接口文档维护枚举值的问题，特别是前后端协作时通过OpenAPI标准协议来维护枚举值的问题。这里我们提供了专门的工具来维护这些枚举值，具体请参考章节：枚举维护-gen enums