9.3.7 الگو State

 1package main
 2
 3import "fmt"
 4
 5type vendingMachine struct {
 6    hasItem       state
 7    itemRequested state
 8    hasMoney      state
 9    noItem        state
10
11    currentState state
12
13    itemCount int
14    itemPrice int
15}
16
17func newVendingMachine(itemCount, itemPrice int) *vendingMachine {
18    v := &vendingMachine{
19        itemCount: itemCount,
20        itemPrice: itemPrice,
21    }
22    hasItemState := &hasItemState{
23        vendingMachine: v,
24    }
25    itemRequestedState := &itemRequestedState{
26        vendingMachine: v,
27    }
28    hasMoneyState := &hasMoneyState{
29        vendingMachine: v,
30    }
31    noItemState := &noItemState{
32        vendingMachine: v,
33    }
34
35    v.setState(hasItemState)
36    v.hasItem = hasItemState
37    v.itemRequested = itemRequestedState
38    v.hasMoney = hasMoneyState
39    v.noItem = noItemState
40    return v
41}
42
43func (v *vendingMachine) requestItem() error {
44    return v.currentState.requestItem()
45}
46
47func (v *vendingMachine) addItem(count int) error {
48    return v.currentState.addItem(count)
49}
50
51func (v *vendingMachine) insertMoney(money int) error {
52    return v.currentState.insertMoney(money)
53}
54
55func (v *vendingMachine) dispenseItem() error {
56    return v.currentState.dispenseItem()
57}
58
59func (v *vendingMachine) setState(s state) {
60    v.currentState = s
61}
62
63func (v *vendingMachine) incrementItemCount(count int) {
64    fmt.Printf("Adding %d items\n", count)
65    v.itemCount = v.itemCount + count
66}

1package main
2
3type state interface {
4    addItem(int) error
5    requestItem() error
6    insertMoney(money int) error
7    dispenseItem() error
8}

 1package main
 2
 3import "fmt"
 4
 5type noItemState struct {
 6    vendingMachine *vendingMachine
 7}
 8
 9func (i *noItemState) requestItem() error {
10    return fmt.Errorf("Item out of stock")
11}
12
13func (i *noItemState) addItem(count int) error {
14    i.vendingMachine.incrementItemCount(count)
15    i.vendingMachine.setState(i.vendingMachine.hasItem)
16    return nil
17}
18
19func (i *noItemState) insertMoney(money int) error {
20    return fmt.Errorf("Item out of stock")
21}
22func (i *noItemState) dispenseItem() error {
23    return fmt.Errorf("Item out of stock")
24}

 1package main
 2
 3import "fmt"
 4
 5type hasItemState struct {
 6    vendingMachine *vendingMachine
 7}
 8
 9func (i *hasItemState) requestItem() error {
10    if i.vendingMachine.itemCount == 0 {
11        i.vendingMachine.setState(i.vendingMachine.noItem)
12        return fmt.Errorf("No item present")
13    }
14    fmt.Printf("Item requestd\n")
15    i.vendingMachine.setState(i.vendingMachine.itemRequested)
16    return nil
17}
18
19func (i *hasItemState) addItem(count int) error {
20    fmt.Printf("%d items added\n", count)
21    i.vendingMachine.incrementItemCount(count)
22    return nil
23}
24
25func (i *hasItemState) insertMoney(money int) error {
26    return fmt.Errorf("Please select item first")
27}
28func (i *hasItemState) dispenseItem() error {
29    return fmt.Errorf("Please select item first")
30}

 1package main
 2
 3import "fmt"
 4
 5type itemRequestedState struct {
 6    vendingMachine *vendingMachine
 7}
 8
 9func (i *itemRequestedState) requestItem() error {
10    return fmt.Errorf("Item already requested")
11}
12
13func (i *itemRequestedState) addItem(count int) error {
14    return fmt.Errorf("Item Dispense in progress")
15}
16
17func (i *itemRequestedState) insertMoney(money int) error {
18    if money < i.vendingMachine.itemPrice {
19        fmt.Errorf("Inserted money is less. Please insert %d", i.vendingMachine.itemPrice)
20    }
21    fmt.Println("Money entered is ok")
22    i.vendingMachine.setState(i.vendingMachine.hasMoney)
23    return nil
24}
25
26func (i *itemRequestedState) dispenseItem() error {
27    return fmt.Errorf("Please insert money first")
28}

 1package main
 2
 3import "fmt"
 4
 5type hasMoneyState struct {
 6    vendingMachine *vendingMachine
 7}
 8
 9func (i *hasMoneyState) requestItem() error {
10    return fmt.Errorf("Item dispense in progress")
11}
12
13func (i *hasMoneyState) addItem(count int) error {
14    return fmt.Errorf("Item dispense in progress")
15}
16
17func (i *hasMoneyState) insertMoney(money int) error {
18    return fmt.Errorf("Item out of stock")
19}
20
21func (i *hasMoneyState) dispenseItem() error {
22    fmt.Println("Dispensing Item")
23    i.vendingMachine.itemCount = i.vendingMachine.itemCount - 1
24    if i.vendingMachine.itemCount == 0 {
25        i.vendingMachine.setState(i.vendingMachine.noItem)
26    } else {
27        i.vendingMachine.setState(i.vendingMachine.hasItem)
28    }
29    return nil
30}

 1package main
 2
 3import (
 4    "fmt"
 5    "log"
 6)
 7
 8func main() {
 9    vendingMachine := newVendingMachine(1, 10)
10    err := vendingMachine.requestItem()
11    if err != nil {
12        log.Fatalf(err.Error())
13    }
14    err = vendingMachine.insertMoney(10)
15    if err != nil {
16        log.Fatalf(err.Error())
17    }
18    err = vendingMachine.dispenseItem()
19    if err != nil {
20        log.Fatalf(err.Error())
21    }
22
23    fmt.Println()
24    err = vendingMachine.addItem(2)
25    if err != nil {
26        log.Fatalf(err.Error())
27    }
28
29    fmt.Println()
30
31    err = vendingMachine.requestItem()
32    if err != nil {
33        log.Fatalf(err.Error())
34    }
35
36    err = vendingMachine.insertMoney(10)
37    if err != nil {
38        log.Fatalf(err.Error())
39    }
40
41    err = vendingMachine.dispenseItem()
42    if err != nil {
43        log.Fatalf(err.Error())
44    }
45}

1Item requestd
2Money entered is ok
3Dispensing Item
4
5Adding 2 items
6
7Item requestd
8Money entered is ok
9Dispensing Item