Option

The Option type represents an optional value. It can be either Some(value) containing a value, or None representing the absence of a value. This is a type-safe alternative to using nil or zero values.

Basic Usage

Creating Options

import "github.com/IBM/fp-go/option"

// Create an Option with a value
some := option.Some(42)

// Create an empty Option
none := option.None[int]()

Checking for Values

// Check if an Option contains a value
if option.IsSome(some) {
    fmt.Println("Has a value")
}

// Check if an Option is empty
if option.IsNone(none) {
    fmt.Println("No value")
}

Extracting Values

// Get the value or provide a default
value := option.GetOrElse(func() int { return 0 })(some)
// value = 42

// Get the value from None with default
value = option.GetOrElse(func() int { return 0 })(none)
// value = 0

Practical Example

Here's a practical example of using Option to handle optional configuration:

import (
    "github.com/IBM/fp-go/option"
    "github.com/IBM/fp-go/function"
)

type Config struct {
    Port option.Option[int]
    Host option.Option[string]
}

func getPort(config Config) int {
    return function.Pipe1(
        config.Port,
        option.GetOrElse(func() int { return 8080 }),
    )
}

func main() {
    // Config with explicit port
    config1 := Config{
        Port: option.Some(3000),
        Host: option.Some("localhost"),
    }
    fmt.Println(getPort(config1)) // 3000

    // Config without port (uses default)
    config2 := Config{
        Port: option.None[int](),
        Host: option.Some("localhost"),
    }
    fmt.Println(getPort(config2)) // 8080
}

Why Use Option?

• Type Safety: The compiler ensures you handle both cases (Some and None)
• Explicit Intent: Makes it clear when a value might be absent
• Composability: Works seamlessly with other fp-go functions
• No Nil Panics: Eliminates nil pointer dereference errors