假如让你来设计group api, 你该怎么设计呢？

group api 和普通api的区别在于前缀不同，如果group api的版本为v1.0 那么相对应的url为/v1.0/xxx, 如果是普通api的话那么api相对应的版本为/xxx

在gin web framework 中设计的原则也是以相对路径来区分。

// RouterGroup is used internally to configure router, a RouterGroup is associated with// a prefix and an array of handlers (middleware).type RouterGroup struct {	Handlers HandlersChain #处理函数	basePath string  #相对路径	engine   *Engine #存在哪个engine上	root     bool  #基于基树判断是否为root}

先看gin中group 的添加规则：

router := gin.New()	users := router.Group("/users")

先看gin.New()默认的basePath是什么。

// New returns a new blank Engine instance without any middleware attached.// By default the configuration is:// - RedirectTrailingSlash:  true// - RedirectFixedPath:      false// - HandleMethodNotAllowed: false// - ForwardedByClientIP:    true// - UseRawPath:             false// - UnescapePathValues:     truefunc New() *Engine {	debugPrintWARNINGNew()	engine := &Engine{		RouterGroup: RouterGroup{			Handlers: nil,			basePath: "/",  #默认为“/”			root:     true,		},		FuncMap:                template.FuncMap{},		RedirectTrailingSlash:  true,		RedirectFixedPath:      false,		HandleMethodNotAllowed: false,		ForwardedByClientIP:    true,		AppEngine:              defaultAppEngine,		UseRawPath:             false,		UnescapePathValues:     true,		MaxMultipartMemory:     defaultMultipartMemory,		trees:                  make(methodTrees, 0, 9),		delims:                 render.Delims{Left: "{
   {", Right: "}}"},		secureJsonPrefix:       "while(1);",	}	engine.RouterGroup.engine = engine	engine.pool.New = func() interface{} {		return engine.allocateContext()	}	return engine}

　　

查看router.Group("/users") 的调用

// Group creates a new router group. You should add all the routes that have common middlewares or the same path prefix.// For example, all the routes that use a common middleware for authorization could be grouped.func (group *RouterGroup) Group(relativePath string, handlers ...HandlerFunc) *RouterGroup {	return &RouterGroup{		Handlers: group.combineHandlers(handlers),		basePath: group.calculateAbsolutePath(relativePath), #根据relativePath这个参数，计算basePath		engine:   group.engine,	}}

　查看group.calculateAbsolutePath(relativePath) 的调用

func (group *RouterGroup) calculateAbsolutePath(relativePath string) string {	return joinPaths(group.basePath, relativePath)}

　再查看joinPaths的实现

func joinPaths(absolutePath, relativePath string) string {	if relativePath == "" { #如果没有relativePath 直接返回absolutePath,默认为“/”		return absolutePath	}        #处理最后的“/”	finalPath := path.Join(absolutePath, relativePath)	appendSlash := lastChar(relativePath) == '/' && lastChar(finalPath) != '/'	if appendSlash {		return finalPath + "/"	}	return finalPath}