4_unpack_example_test.go

package mu_test

import (
	"errors"
	"fmt"

	"github.com/appthrust/mu"
)

// ExampleResult_Unpack demonstrates converting Result back to Go's (value, error) pattern
func ExampleResult_Unpack() {
	// Ok result unpacks to (value, nil)
	okResult := mu.Ok(42)
	value, err := okResult.Unpack()
	fmt.Printf("Ok result: value=%d, err=%v\n", value, err)

	// Err result unpacks to (zero_value, error)
	errResult := mu.Err[int](errors.New("something went wrong"))
	value, err = errResult.Unpack()
	fmt.Printf("Err result: value=%d, err=%v\n", value, err)

	// Output:
	// Ok result: value=42, err=<nil>
	// Err result: value=0, err=something went wrong
}

// ExampleResult_Unpack_withFunctions demonstrates using Unpack with functions
func ExampleResult_Unpack_withFunctions() {
	// Function that returns Result
	divide := func(a, b int) mu.Result[int] {
		if b == 0 {
			return mu.Err[int](errors.New("division by zero"))
		}
		return mu.Ok(a / b)
	}

	// Convert Result back to Go pattern for traditional error handling
	handleDivision := func(a, b int) {
		value, err := divide(a, b).Unpack()
		if err != nil {
			fmt.Printf("Error: %v\n", err)
			return
		}
		fmt.Printf("Result: %d\n", value)
	}

	handleDivision(10, 2)
	handleDivision(10, 0)

	// Output:
	// Result: 5
	// Error: division by zero
}

// ExampleResult_Unpack_bridgeToLegacyCode shows bridging mu.Result to legacy Go code
func ExampleResult_Unpack_bridgeToLegacyCode() {
	// Legacy function that expects (value, error)
	processData := func(data string, err error) {
		if err != nil {
			fmt.Printf("Processing failed: %v\n", err)
			return
		}
		fmt.Printf("Processing: %s\n", data)
	}

	// Modern function that returns Result
	fetchData := func(id int) mu.Result[string] {
		if id <= 0 {
			return mu.Err[string](errors.New("invalid ID"))
		}
		return mu.Ok(fmt.Sprintf("data-%d", id))
	}

	// Bridge between modern and legacy code
	data, err := fetchData(123).Unpack()
	processData(data, err)

	data, err = fetchData(-1).Unpack()
	processData(data, err)

	// Output:
	// Processing: data-123
	// Processing failed: invalid ID
}