39 lines
565 B
Go
39 lines
565 B
Go
|
package main
|
||
|
|
|
||
|
|
import (
|
||
|
|
"errors"
|
||
|
|
"fmt"
|
||
|
|
)
|
||
|
|
|
||
|
|
type Bitcoin int
|
||
|
|
|
||
|
|
type Stringer interface {
|
||
|
|
String() string
|
||
|
|
}
|
||
|
|
|
||
|
|
type Wallet struct {
|
||
|
|
balance Bitcoin
|
||
|
|
}
|
||
|
|
|
||
|
|
var ErrInsufficientFunds = errors.New("cannot withdraw, insufficient funds")
|
||
|
|
|
||
|
|
func (w *Wallet) Deposit(amount Bitcoin) {
|
||
|
|
w.balance += amount
|
||
|
|
}
|
||
|
|
|
||
|
|
func (w *Wallet) Withdraw(amount Bitcoin) error {
|
||
|
|
if amount > w.balance {
|
||
|
|
return ErrInsufficientFunds
|
||
|
|
}
|
||
|
|
w.balance -= amount
|
||
|
|
return nil
|
||
|
|
}
|
||
|
|
|
||
|
|
func (w *Wallet) Balance() Bitcoin {
|
||
|
|
return w.balance
|
||
|
|
}
|
||
|
|
|
||
|
|
func (b Bitcoin) String() string {
|
||
|
|
return fmt.Sprintf("%d BTC", b)
|
||
|
|
}
|