# 工具包插件
插件是將外部代碼集成到Micro工具箱的一種方式。這與Micro插件完全分開。這里使用的插件，允許您在工具包中添加額外的標志，命令和HTTP處理程序。
## 怎么運行的？
在`micro/plugin`下有一個全局插件管理器，它包含整個工具包中使用的插件。可以通過調用`plugin.Register`來注冊插件。每個組件（api，web，sidecar，cli，bot）都有一個單獨的插件管理器，用于注冊只作為該組件一部分的添加插件。它們可以通過稱為`api.Register`，`web.Register`等以相同的方式使用。
這是接口
```
// Plugin is the interface for plugins to micro. It differs from go-micro in that it's for
// the micro API, Web, Sidecar, CLI. It's a method of building middleware for the HTTP side.
type Plugin interface {
// Global Flags
Flags() []cli.Flag
// Sub-commands
Commands() []cli.Command
// Handle is the middleware handler for HTTP requests. We pass in
// the existing handler so it can be wrapped to create a call chain.
Handler() Handler
// Init called when command line args are parsed.
// The initialised cli.Context is passed in.
Init(*cli.Context) error
// Name of the plugin
String() string
}
// Manager is the plugin manager which stores plugins and allows them to be retrieved.
// This is used by all the components of micro.
type Manager interface {
Plugins() map[string]Plugin
Register(name string, plugin Plugin) error
}
// Handler is the plugin middleware handler which wraps an existing http.Handler passed in.
// Its the responsibility of the Handler to call the next http.Handler in the chain.
type Handler func(http.Handler) http.Handler
```
## 如何使用它
這里有一個簡單的插件示例，它添加一個標志，然后打印該值。
### 插件
在頂級目錄中創建一個plugin.go文件。
```
package main
import (
"log"
"github.com/micro/cli"
"github.com/micro/micro/plugin"
)
func init() {
plugin.Register(plugin.NewPlugin(
plugin.WithName("example"),
plugin.WithFlag(cli.StringFlag{
Name: "example_flag",
Usage: "This is an example plugin flag",
EnvVar: "EXAMPLE_FLAG",
Value: "avalue",
}),
plugin.WithInit(func(ctx *cli.Context) error {
log.Println("Got value for example_flag", ctx.String("example_flag"))
return nil
}),
))
}
```
### 構建代碼
只需使用該插件構建micro。
```
go build -o micro ./main.go ./plugin.go
```
## 知識庫
該工具包的插件可以在中找到[github.com/micro/go-plugins/micro](https://github.com/micro/go-plugins/tree/master/micro)。
