Functions — Programuoki

Code

Refactor main.go — printing becomes functions

Keep your three variables exactly as they are — we're not touching them. The change is where the printing lives: pull it out of main into small, named functions.

Add these three functions below main:

// printHeader prints the app title line.
func printHeader() {
	fmt.Println("App:", appName)
}

// formatItem BUILDS the one-line summary and returns it (prints nothing).
func formatItem(title string, pages int, read bool) string {
	return fmt.Sprintf("Book: %s | pages: %d | read: %v", title, pages, read)
}

// printItem calls formatItem and prints the result.
func printItem(title string, pages int, read bool) {
	fmt.Println(formatItem(title, pages, read))
}

Then replace the two print lines in main with two calls:

	printHeader()
	printItem(title, pages, read)

Why split formatItem from printItem? Because formatItem returns the line instead of printing it — so later you can reuse it (e.g. writing the line to a file). printItem just prints what formatItem built. All the logic moved out of main.

Verify. The output must be exactly the same as in lesson 2:

App: Book list
Book: The Go Programming Language | pages: 380 | read: false

Tip. This is the heart of refactoring: a good refactor does not change the program's behavior — only the shape of the code. If the output changed, you broke something.

main.go MODIFY 16 lines changed

Edit this file in ./

package main

import "fmt"

// appName never changes while the program runs — a constant.
const appName = "Book list"

func main() {
	// Last lesson you wrote your fields on paper — now they are variables.
	var title string = "The Go Programming Language" // full form: var + name + type
	pages := 380                                     // short form: type inferred (int)
	read := false                                    // bool: true or false

	printHeader()
	printItem(title, pages, read)
}

// printHeader prints the app title line.
func printHeader() {
	fmt.Println("App:", appName)
}

// formatItem builds the one-line summary for a single record.
func formatItem(title string, pages int, read bool) string {
	return fmt.Sprintf("Book: %s | pages: %d | read: %v", title, pages, read)
}

// printItem prints the summary built by formatItem.
func printItem(title string, pages int, read bool) {
	fmt.Println(formatItem(title, pages, read))
}