Revel命令列工具源碼閱讀

這是一個建立於 的文章，其中的資訊可能已經有所發展或是發生改變。

這一篇來詳細看下revel命令列工具。下面是這個包的幾個檔案，以及對應的功能說明。

檔案名稱	短描述(Short)	完整描述(Long)
clean.go	clean a Revel application’s temp files	Clean the Revel web application named by the given import path. For example: revel clean github.com/robfig/revel/samples/chat It removes the app/tmp directory.
new.go	create a skeleton Revel application	New creates a few files to get a new Revel application running quickly. It puts all of the files in the given import path, taking the final element in the path to be the app name. For example: revel new import/path/helloworld
package.go	package a Revel application (e.g. for deployment)	Package the Revel web application named by the given import path. This allows it to be deployed and run on a machine that lacks a Go installation. For example: revel package github.com/robfig/revel/samples/chat
run.go	run a Revel application	Run the Revel web application named by the given import path. For example, to run the chat room sample application: revel run github.com/robfig/revel/samples/chat dev The run mode is used to select which set of app.conf configuration should apply and may be used to determine logic in the application itself. Run mode defaults to “dev”. You can set a port as an optional third parameter. For revel run github.com/robfig/revel/samples/chat prod 8080
test.go	run all tests from the command-line	Run all tests for the Revel app named by the given import path. For example, to run the booking sample application’s tests: revel test github.com/robfig/revel/samples/booking dev The run mode is used to select which set of app.conf configuration should apply and may be used to determine logic in the application itself. Run mode defaults to “dev”.

以上幾個檔案分別對應命令列工具的幾個命令，而剩下的幾個檔案及其作用如下：

檔案名稱	作用
package_run.bat.template	windows下運行指令碼模板
package_run.sh.template	linux下運行指令碼模板
rev.go	主函數以及命令解析，運行
util.go	工具函數集合

我們需要先瞭解rev.go檔案中以下的程式碼片段：

// Cribbed from the genius organization of the "go" command.
type Command struct {
Run func(args []string)
UsageLine, Short, Long string
}

func (cmd *Command) Name() string {
name := cmd.UsageLine
i := strings.Index(name, " ")
if i >= 0 {
name = name[:i]
}
return name
}

var commands = []*Command{
cmdRun,
cmdNew,
cmdClean,
cmdPackage,
cmdTest,
}

1. Command結構很簡單，Run來用儲存命令的處理函數，而其他三個參數則用來儲存命令的形式，簡單描述以及完整描述。例如：
   var cmdNew = &Command{
   UsageLine: "new [path]",
   Short: "create a skeleton Revel application",
   Long:
   New creates a few files to get a new Revel application running quickly.

   It puts all of the files in the given import path, taking the final element in
   the path to be the app name.

   For example:

   revel new import/path/helloworld
,
   }

2. Name函數從UsageLine讀取命令名，例如：run，new等。
3. commands是一個*Command類型數組，儲存了所有命令的*Command，例如：cmdNew，它是在new.go檔案中定義，注意該結構中Run變數的值則是在init函數獲得，例如：

   func init() {
   cmdNew.Run = newApp
   }
   func newApp(args []string) {
   …
   }

當我們使用類似：revel new myapp的命令時，rev包中的main函數將被調用，並解析其中的參數，接著調用對應命令的Run函數，程式碼片段如下：

for _, cmd := range commands {
if cmd.Name() == args[0] {
cmd.Run(args[1:])
return
}
}

rev.go中剩餘一些細節也比較簡單，這裡就不逐行解釋了。
這一篇就到這裡。