结构体套结构体指针--有什么黑魔法么

在看 k8s 源代码时候，有这么一段代码，其中 Complete()方法， 看注释是可以填充没有设置的字段，填充字段需要这么套娃么.

CompletedConfig --》 指针 completedConfig --》 Config 指针

// Config is the main context object for the controller manager. type Config struct { ComponentConfig kubectrlmgrconfig.KubeControllerManagerConfiguration SecureServing *apiserver.SecureServingInfo // LoopbackClientConfig is a config for a privileged loopback connection LoopbackClientConfig *restclient.Config // TODO: remove deprecated insecure serving InsecureServing *apiserver.DeprecatedInsecureServingInfo Authentication apiserver.AuthenticationInfo Authorization apiserver.AuthorizationInfo // the general kube client Client *clientset.Clientset // the client only used for leader election LeaderElectionClient *clientset.Clientset // the rest config for the master Kubeconfig *restclient.Config // the event sink EventRecorder record.EventRecorder } type completedConfig struct { *Config } // CompletedConfig same as Config, just to swap private object. type CompletedConfig struct { // Embed a private pointer that cannot be instantiated outside of this package. *completedConfig } // Complete fills in any fields not set that are required to have valid data. It's mutating the receiver. func (c *Config) Complete() *CompletedConfig { cc := completedConfig{c} apiserver.AuthorizeClientBearerToken(c.LoopbackClientConfig, &c.Authentication, &c.Authorization) return &CompletedConfig{&cc} }