Go语言教程之边写边学：编写并测试程序 ：完成银行项目功能

实现转账方法

• 你需要实现向其他帐户转账的功能。 在本例中，你必须使用至少两个帐户来初始化程序，而不是像之前一样只使用一个帐户。
• 由于你要在核心程序包中添加新方法，因此请首先创建测试用例，以确保你编写正确的逻辑来进行转账。 请密切注意在函数与指针之间进行通信的方式。
• 你的转账方法应当接收你要转账的金额以及你将在其中增加资金的帐户对象。 请确保重用存款和取款方法以避免重复(特别是对于错误处理)。
• 请记住，如果你没有足够的资金，则无法向其他帐户转账。

修改对账单终结点以返回JSON对象

"{\"Name\":\"John\",\"Address\":\"Los Angeles, California\",\"Phone\":\"(213) 555 0147\",\"Number\":1001,\"Balance\":0}"

//...

func TestTransfer(t *testing.T) {
    accountA := Account{
		Customer: Customer{
			Name:    "John",
			Address: "Los Angeles, California",
			Phone:   "(213) 555 0147",
		},
		Number:  1001,
		Balance: 0,
	}

	accountB := Account{
		Customer: Customer{
			Name:    "Mark",
			Address: "Irvine, California",
			Phone:   "(949) 555 0198",
		},
		Number:  1002,
		Balance: 0,
	}

	accountA.Deposit(100)
	err := accountA.Transfer(50, &accountB)

	if accountA.Balance != 50 && accountB.Balance != 50 {
		t.Error("transfer from account A to account B is not working", err)
	}
}

银行核心：bank.go

package bank

import (
	"errors"
	"fmt"
)

//...

// Transfer function
func (a *Account) Transfer(amount float64, dest *Account) error {
	if amount <= 0 {
		return errors.New("the amount to transfer should be greater than zero")
	}

	if a.Balance < amount {
		return errors.New("the amount to transfer should be greater than the account's balance")
	}

	a.Withdraw(amount)
	dest.Deposit(amount)
	return nil
}

// Bank ...
type Bank interface {
	Statement() string
}

// Statement ...
func Statement(b Bank) string {
	return b.Statement()
}

银行API：main.go

package main

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"strconv"

	"github.com/msft/bank"
)

var accounts = map[float64]*CustomAccount{}

func main() {
	accounts[1001] = &CustomAccount{
		Account: &bank.Account{
			Customer: bank.Customer{
				Name:    "John",
				Address: "Los Angeles, California",
				Phone:   "(213) 555 0147",
			},
			Number: 1001,
		},
	}

	accounts[1002] = &CustomAccount{
		Account: &bank.Account{
			Customer: bank.Customer{
				Name:    "Mark",
				Address: "Irvine, California",
				Phone:   "(949) 555 0198",
			},
			Number: 1002,
		},
	}

	http.HandleFunc("/statement", statement)
	http.HandleFunc("/deposit", deposit)
	http.HandleFunc("/withdraw", withdraw)
	http.HandleFunc("/transfer", transfer)
	log.Fatal(http.ListenAndServe("localhost:8000", nil))
}

//...

func transfer(w http.ResponseWriter, req *http.Request) {
	numberqs := req.URL.Query().Get("number")
	amountqs := req.URL.Query().Get("amount")
	destqs := req.URL.Query().Get("dest")

	if numberqs == "" {
		fmt.Fprintf(w, "Account number is missing!")
		return
	}

	if number, err := strconv.ParseFloat(numberqs, 64); err != nil {
		fmt.Fprintf(w, "Invalid account number!")
	} else if amount, err := strconv.ParseFloat(amountqs, 64); err != nil {
		fmt.Fprintf(w, "Invalid amount number!")
	} else if dest, err := strconv.ParseFloat(destqs, 64); err != nil {
		fmt.Fprintf(w, "Invalid account destination number!")
	} else {
		if accountA, ok := accounts[number]; !ok {
			fmt.Fprintf(w, "Account with number %v can't be found!", number)
		} else if accountB, ok := accounts[dest]; !ok {
			fmt.Fprintf(w, "Account with number %v can't be found!", dest)
		} else {
			err := accountA.Transfer(amount, accountB.Account)
			if err != nil {
				fmt.Fprintf(w, "%v", err)
			} else {
				fmt.Fprintf(w, accountA.Statement())
			}
		}
	}
}

func statement(w http.ResponseWriter, req *http.Request) {
	numberqs := req.URL.Query().Get("number")

	if numberqs == "" {
		fmt.Fprintf(w, "Account number is missing!")
		return
	}

	number, err := strconv.ParseFloat(numberqs, 64)
	if err != nil {
		fmt.Fprintf(w, "Invalid account number!")
	} else {
		account, ok := accounts[number]
		if !ok {
			fmt.Fprintf(w, "Account with number %v can't be found!", number)
		} else {
			json.NewEncoder(w).Encode(bank.Statement(account))
		}
	}
}

// CustomAccount ...
type CustomAccount struct {
	*bank.Account
}

// Statement ...
func (c *CustomAccount) Statement() string {
	json, err := json.Marshal(c)
	if err != nil {
		return err.Error()
	}

	return string(json)
}