# 工具包

插件是将外部代码集成到Micro工具箱的一种方式。这与Micro插件完全分开。这里使用的插件，允许您在工具包中添加额外的标志，命令和HTTP处理程序。

## 怎么运行的？

在`micro/plugin`下有一个全局插件管理器，它包含整个工具包中使用的插件。可以通过调用`plugin.Register`来注册插件。每个组件（api，web，sidecar，cli，bot）都有一个单独的插件管理器，用于注册只作为该组件一部分的添加插件。它们可以通过称为`api.Register`，`web.Register`等以相同的方式使用。

这是接口

```
// 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

这里有一个简单的插件示例，它添加一个标志，然后打印该值。

### 插件

在顶级目录中创建一个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
        }),
    ))
}
```

### 构建代码

只需使用该插件构建micro。

```
go build -o micro ./main.go ./plugin.go
```

## 知识库

该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)。


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