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47 lines
1.3 KiB
Go
47 lines
1.3 KiB
Go
package pointers_errors
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import "fmt"
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type Stringer interface {
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String() string
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}
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// creating a new type from an existing on
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// The idea being it could be more descriptive
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// but also you can declare methods on them
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// which can be used to add domain specific functionality
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type Bitcoin int
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// this let's us use fmt strings with %s on the Bitcoin type
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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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balance Bitcoin
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}
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func (w *Wallet) Deposit(amount Bitcoin) {
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// Need a pointer because the func args are copied
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// so w Wallet is a copy of wallet. Not the actually refernce to the
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// wallet that Deposit was called on.
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// Notice we don't have to derefence the pointer like in Balance because
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// in go https://go.dev/ref/spec#Method_values struct pointers are automatically
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// derefenced
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w.balance += amount
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}
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// Technically you do not need to change Balance to use a pointer receiver as taking a copy of the balance is fine. However, by convention you should keep your method receiver types the same for consistency.
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func (w *Wallet) Balance() Bitcoin {
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// dereferences the pointer
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// which as stated above didn't need to happen because go automatically
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// dereferences struct pointers.
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return (*w).balance
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}
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func (w *Wallet) Withdraw(amount Bitcoin) {
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w.balance -= amount
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}
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