职责链模式
职责链模式用于分离不同职责，并且动态组合相关职责。
Golang实现职责链模式时候，因为没有继承的支持，使用链对象包涵职责的方式，即：
- 链对象包含当前职责对象以及下一个职责链。
- 职责对象提供接口表示是否能处理对应请求。
- 职责对象提供处理函数处理相关职责。
同时可在职责链类中实现职责接口相关函数，使职责链对象可以当做一般职责对象是用。
chain.go
package chain import "fmt" type Manager interface { HaveRight(money int) bool HandleFeeRequest(name string, money int) bool } type RequestChain struct { Manager successor *RequestChain } func (r *RequestChain) SetSuccessor(m *RequestChain) { r.successor = m } func (r *RequestChain) HandleFeeRequest(name string, money int) bool { if r.Manager.HaveRight(money) { return r.Manager.HandleFeeRequest(name, money) } if r.successor != nil { return r.successor.HandleFeeRequest(name, money) } return false } func (r *RequestChain) HaveRight(money int) bool { return true } type ProjectManager struct{} func NewProjectManagerChain() *RequestChain { return &RequestChain{ Manager: &ProjectManager{}, } } func (*ProjectManager) HaveRight(money int) bool { return money < 500 } func (*ProjectManager) HandleFeeRequest(name string, money int) bool { if name == "bob" { fmt.Printf("Project manager permit %s %d fee request\n", name, money) return true } fmt.Printf("Project manager don't permit %s %d fee request\n", name, money) return false } type DepManager struct{} func NewDepManagerChain() *RequestChain { return &RequestChain{ Manager: &DepManager{}, } } func (*DepManager) HaveRight(money int) bool { return money < 5000 } func (*DepManager) HandleFeeRequest(name string, money int) bool { if name == "tom" { fmt.Printf("Dep manager permit %s %d fee request\n", name, money) return true } fmt.Printf("Dep manager don't permit %s %d fee request\n", name, money) return false } type GeneralManager struct{} func NewGeneralManagerChain() *RequestChain { return &RequestChain{ Manager: &GeneralManager{}, } } func (*GeneralManager) HaveRight(money int) bool { return true } func (*GeneralManager) HandleFeeRequest(name string, money int) bool { if name == "ada" { fmt.Printf("General manager permit %s %d fee request\n", name, money) return true } fmt.Printf("General manager don't permit %s %d fee request\n", name, money) return false }
chain_test.go
package chain func ExampleChain() { c1 := NewProjectManagerChain() c2 := NewDepManagerChain() c3 := NewGeneralManagerChain() c1.SetSuccessor(c2) c2.SetSuccessor(c3) var c Manager = c1 c.HandleFeeRequest("bob", 400) c.HandleFeeRequest("tom", 1400) c.HandleFeeRequest("ada", 10000) c.HandleFeeRequest("floar", 400) // Output: // Project manager permit bob 400 fee request // Dep manager permit tom 1400 fee request // General manager permit ada 10000 fee request // Project manager don't permit floar 400 fee request }
