tulkdan.dev
+38
Go/pointers/pointer.go
+38
Go/pointers/pointer.go
···
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package pointers
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import (
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"fmt"
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"errors"
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)
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type Bitcoin int
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type Stringer interface {
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String() string
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}
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func (b Bitcoin) String() string {
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return fmt.Sprintf("%d BTC", b)
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}
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type Wallet struct {
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// when using lowercase properties names, it will be private
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balance Bitcoin
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}
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func (w *Wallet) Deposit(amount Bitcoin) {
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w.balance += amount
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}
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func (w *Wallet) Balance() Bitcoin {
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return w.balance
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}
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func (w *Wallet) Withdraw(amount Bitcoin) error {
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if amount > w.balance {
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return errors.New("cannot withdraw, insufficient funds")
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}
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w.balance -= amount
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return nil
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}
+61
Go/pointers/pointer_test.go
+61
Go/pointers/pointer_test.go
···
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package pointers
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import "testing"
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func TestWallet(t *testing.T) {
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t.Run("deposit", func(t *testing.T) {
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wallet := Wallet{}
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wallet.Deposit(Bitcoin(10))
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assertBalance(t, wallet, Bitcoin(10))
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})
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t.Run("withdraw", func(t *testing.T) {
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wallet := Wallet{balance: Bitcoin(20)}
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err := wallet.Withdraw(Bitcoin(10))
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assertNoError(t, err)
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assertBalance(t, wallet, Bitcoin(10))
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})
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t.Run("withdraw insufficient funds", func(t *testing.T) {
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startingBalance := Bitcoin(20)
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wallet := Wallet{startingBalance}
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err := wallet.Withdraw(Bitcoin(100))
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assertError(t, err, "cannot withdraw, insufficient funds")
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assertBalance(t, wallet, startingBalance)
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})
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}
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func assertBalance(t testing.TB, wallet Wallet, want Bitcoin) {
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t.Helper()
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got := wallet.Balance()
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if got != want {
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t.Errorf("got %s want %s", got, want)
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}
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}
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func assertNoError(t testing.TB, got error) {
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t.Helper()
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if got != nil {
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t.Fatal("got an error butt didn't want one")
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}
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}
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func assertError(t testing.TB, got error, want string) {
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t.Helper()
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if got == nil {
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t.Fatal("didn't get an error but wanted one")
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}
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if got.Error() != want {
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t.Errorf("got %q, want %q", got, want)
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}
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}