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Ejercicios de Go

Bank Account in Go with Errors

A struct, pointer methods and your own error types: deposits and withdrawals that can fail safely.

  • Principiante
  • 5 min de lectura
  • 1 ejemplo ejecutable
Lo que aprenderás
  • Methods that return error
  • A custom error type
  • Unexported fields
Ejecutar código →
Operation → result
Deposit(50)<nil>
Withdraw(500)insufficient funds
Withdraw(120)<nil>, balance 30

Every operation can succeed or fail

This exercise combines a struct, pointer methods and error handling. Each operation returns an error, and the error says exactly what went wrong.

Deposit rejects amounts that are not positive and Withdraw rejects an amount larger than the balance, so the balance can never become invalid. balance starts with a lower-case letter, so code outside the package cannot change it directly. A nil error prints as <nil>.

Puntos clave

  1. Deposit rejects amounts that are not positive.
  2. Withdraw rejects more than the balance.
  3. balance is unexported, so only the methods change it.

Ejemplo ejecutable de Go

Go
Ejecutar código →
main.go
package main

import (
	"errors"
	"fmt"
)

var ErrInvalidAmount = errors.New("amount must be positive")

type InsufficientFundsError struct {
	Needed, Available int
}

func (e InsufficientFundsError) Error() string {
	return fmt.Sprintf("insufficient funds: need %d, have %d", e.Needed, e.Available)
}

type Account struct {
	Owner   string
	balance int
}

func (a *Account) Deposit(amount int) error {
	if amount <= 0 {
		return ErrInvalidAmount
	}
	a.balance += amount
	return nil
}

func (a *Account) Withdraw(amount int) error {
	if amount > a.balance {
		return InsufficientFundsError{Needed: amount, Available: a.balance}
	}
	a.balance -= amount
	return nil
}

func main() {
	account := &Account{Owner: "Ada", balance: 100}
	fmt.Println(account.Deposit(50))
	fmt.Println(account.Withdraw(500))
	fmt.Println(account.Deposit(0))
	fmt.Println(account.Withdraw(120))
	fmt.Println(account.Owner, "has", account.balance)
}
Obtén un botón Run para este ejemplo Resultado de ejecutar el código
<nil>
insufficient funds: need 500, have 150
amount must be positive
<nil>
Ada has 30

Practica

Abre el ejemplo en el compilador online, cambia un valor o añade una línea y predice la salida antes de ejecutarlo. Después rompe el código a propósito y lee el mensaje del compilador.

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