mediator pattern

README.md

@@ -38,7 +38,7 @@ A curated collection of idiomatic design & application patterns for Go language.
 |:-------:|:----------- |:------:|
 | [Chain of Responsibility](/behavioral/chain_of_responsibility/main.go) | Avoids coupling a sender to receiver by giving more than object a chance to handle the request | ✔ |
 | [Command](/behavioral/command/main.go) | Bundles a command and arguments to call later | ✔ |
-| [Mediator](/behavioral/mediator.md) | Connects objects and acts as a proxy | ✘ |
+| [Mediator](/behavioral/mediator/main.go) | Connects objects and acts as a proxy | ✔ |
 | [Memento](/behavioral/memento.md) | Generate an opaque token that can be used to go back to a previous state | ✘ |
 | [Observer](/behavioral/observer.md) | Provide a callback for notification of events/changes to data | ✔ |
 | [Registry](/behavioral/registry.md) | Keep track of all subclasses of a given class | ✘ |

behavioral/mediator/main.go

@@ -0,0 +1,76 @@
+// 中介者模式(mediator pattern)
+// 当两个对象存在复杂的依赖关系时，考虑增加一个中介者使之解耦，使他们不需要进行显示的引用.
+// 但问题在于中介本身会去实现复杂的逻辑，进而导致中介者变得复杂臃肿难以维护.
+//
+// 这里是竞价和消息交换的例子.
+// 参与竞价的玩家只需要向中介出价就可以知道是否能买到商品，由中介确定谁的出价高
+package main
+
+import (
+	"log"
+	"math/rand"
+	"time"
+)
+
+// buyer 之间通过中介进行引用
+type Buyer struct {
+	m	*Mediator
+	Name string// unique
+}
+
+func (b Buyer)Bid(price int){
+	if p ,ok := b.m.isMaxPrice(b ,price);ok{
+		log.Println(b.Name ,"are in lead temporarily with" ,p)
+	}else{
+		log.Println(b.Name ,"lose with" ,p)
+	}
+}
+
+type Mediator struct {
+	Buyers map[Buyer]int
+	MaxPrice int
+	MaxPriceBuyer Buyer
+}
+
+func (m *Mediator)isMaxPrice(b Buyer ,price int)(int ,bool){
+	if b.Name == m.MaxPriceBuyer.Name{
+		return m.MaxPrice ,true
+	}
+	m.Buyers[b] = price
+	for k ,v := range m.Buyers{
+		if v > m.MaxPrice{
+			m.MaxPrice = v
+			m.MaxPriceBuyer = k
+		}
+	}
+	if b.Name == m.MaxPriceBuyer.Name{
+		return price ,true
+	}
+	return price ,false
+}
+
+func main(){
+	m := &Mediator{
+		make(map[Buyer]int),
+		0,
+		Buyer{},
+	}
+
+	icg := Buyer{m ,"icg"}
+	nyn := Buyer{m ,"nyn"}
+
+	rand.Seed(time.Now().UnixNano())
+	for i:=0 ;i<3 ;i++{
+		icg.Bid(rand.Intn(10000))
+		nyn.Bid(rand.Intn(10000))
+	}
+	// output:
+	/*
+	2019/05/02 12:19:52 icg are in lead temporarily with 1024
+	2019/05/02 12:19:52 nyn are in lead temporarily with 4232
+	2019/05/02 12:19:52 icg are in lead temporarily with 6412
+	2019/05/02 12:19:52 nyn are in lead temporarily with 6747
+	2019/05/02 12:19:52 icg lose with 4951
+	2019/05/02 12:19:52 nyn are in lead temporarily with 6747
+	 */
+}