一、前言

golang 为了加速编译，不允许包循环引用。通常来说，只要你的包规划得好，严格规范单向调用链（如控制层 -> 业务层 -> 数据层），一般不会出现包循环引用问题。当然现实业务往往不会这么理想，同层级之间的不同包经常需要互相引用，下面我就分享几种解决包循环引用的方案。

二、新建公共接口包（父包），将需要循环调用的函数或方法抽象为接口

  • package_i
package package_i
 
type PackageAInterface interface {
	PrintA()
}
 
type PackageBInterface interface {
	PrintB()
}
  • package_a
package package_a
 
import (
	"cycle/package_i"
	"fmt"
)
 
type PackageA struct {
	B package_i.PackageBInterface
}
 
func (a PackageA) PrintA() {
	fmt.Println("I'm a!")
}
 
func (a PackageA) PrintAll() {
	a.PrintA()
	a.B.PrintB()
}
  • package_b
package package_b
 
import (
	"cycle/package_i"
	"fmt"
)
 
type PackageB struct {
	A package_i.PackageAInterface
}
 
func (b PackageB) PrintB() {
	fmt.Println("I'm b!")
}
 
func (b PackageB) PrintAll() {
	b.PrintB()
	b.A.PrintA()
}
  • main
package main
 
import (
	"cycle/package_a"
	"cycle/package_b"
)
 
func main() {
	a := new(package_a.PackageA)
	b := new(package_b.PackageB)
        a.B = b
        b.A = a
	a.PrintAll()
	b.PrintAll()
}

三、新建公共组合包（子包），在组合包中组合调用

  • package_c
package package_c
 
import (
	"cycle/package_a"
	"cycle/package_b"
)
 
type CombileAB struct {
	A *package_a.PackageA
	B *package_b.PackageB
}
 
func (c CombileAB) PrintAll() {
	c.A.PrintA()
	c.B.PrintB()
}
  • main
package main
 
import (
	"cycle/package_a"
	"cycle/package_b"
	"cycle/package_c"
)
 
func main() {
	a := new(package_a.PackageA)
	b := new(package_b.PackageB)
	c := new(package_c.CombileAB)
	c.A = a
	c.B = b
	c.PrintAll()
}

四、全局存储需要相互依赖的函数，通过关键字进行调用

  • callback_mgr
package callback_mgr
 
import (
	"fmt"
	"reflect"
)
 
var callBackMap map[string]interface{}
 
func init() {
	callBackMap = make(map[string]interface{})
}
 
func RegisterCallBack(key string, callBack interface{}) {
	callBackMap[key] = callBack
}
 
func CallBackFunc(key string, args ...interface{}) []interface{} {
	if callBack, ok := callBackMap[key]; ok {
		in := make([]reflect.Value, len(args))
		for i, arg := range args {
			in[i] = reflect.ValueOf(arg)
		}
		outList := reflect.ValueOf(callBack).Call(in)
		result := make([]interface{}, len(outList))
		for i, out := range outList {
			result[i] = out.Interface()
		}
		return result
	} else {
		panic(fmt.Errorf("callBack(%s) not found", key))
	}
}
  • package_a
package package_a
 
import (
	"cycle/callback_mgr"
	"fmt"
)
 
func init() {
	callback_mgr.RegisterCallBack("getA", new(PackageA).GetA)
}
 
type PackageA struct {
}
 
func (a PackageA) GetA() string {
	return "I'm a!"
}
 
func (a PackageA) PrintAll() {
	fmt.Println(a.GetA())
	fmt.Println(callback_mgr.CallBackFunc("getB")[0].(string))
}
  • package_b
package package_b
 
import (
	"cycle/callback_mgr"
	"fmt"
)
 
func init() {
	callback_mgr.RegisterCallBack("getB", new(PackageB).GetB)
}
 
type PackageB struct {
}
 
func (b PackageB) GetB() string {
	return "I'm b!"
}
 
func (b PackageB) PrintAll() {
	fmt.Println(b.GetB())
	fmt.Println(callback_mgr.CallBackFunc("getA")[0].(string))
}
  • main
package main
 
import (
	"cycle/package_a"
	"cycle/package_b"
)
 
func main() {
	a := new(package_a.PackageA)
	b := new(package_b.PackageB)
	a.PrintAll()
	b.PrintAll()
}

五、不需要回调结果的可以通过事件总线（eventBus）解耦

  • eventBus
package eventBus
 
import (
	"github.com/asaskevich/EventBus"
)
 
var globalEventBus EventBus.Bus
 
func init() {
	globalEventBus = EventBus.New()
}
 
func Subscribe(topic string, fn interface{}) error {
	return globalEventBus.Subscribe(topic, fn)
}
 
func SubscribeAsync(topic string, fn interface{}, transactional bool) error {
	return globalEventBus.SubscribeAsync(topic, fn, transactional)
}
 
func Publish(topic string, args ...interface{}) {
	globalEventBus.Publish(topic, args...)
}
  • package_a
package package_a
 
import (
	"cycle/eventBus"
	"fmt"
)
 
func init() {
	eventBus.Subscribe("PrintA", new(PackageA).PrintA)
}
 
type PackageA struct {
}
 
func (a PackageA) PrintA() {
	fmt.Println("I'm a!")
}
 
func (a PackageA) PrintAll() {
	a.PrintA()
	eventBus.Publish("PrintB")
}
  • package_b
package package_b
 
import (
	"cycle/eventBus"
	"fmt"
)
 
func init() {
	eventBus.Subscribe("PrintB", new(PackageB).PrintB)
}
 
type PackageB struct {
}
 
func (b PackageB) PrintB() {
	fmt.Println("I'm b!")
}
 
func (b PackageB) PrintAll() {
	b.PrintB()
	eventBus.Publish("PrintA")
}