Encapsulation & Package Exports

🐹 Go Language Lesson 11 Intermediate

Encapsulation in Go is simple and clean. Access visibility is determined entirely by whether a variable, field, or function name starts with a capital letter.

1 Capitalization Visibility Rule

Go does not use access modifier keywords like `private`, `public`, or `protected`. Instead, visibility is managed via naming conventions:

Exported (Public): Any struct field, function, or variable starting with an **uppercase letter** is exported and visible outside its declaring package (e.g. `fmt.Println`).
Unexported (Private): Any field or function starting with a **lowercase letter** is private and visible only within its declaring package.

2 Encapsulation Code

Let's look at an example illustrating package structure export boundaries:

Go — Encapsulation ▶ Run Code

package main

import "fmt"

struct BankAccount {
    Owner   string  // Exported (Public)
    balance float64 // Unexported (Private to package)
}

func main() {
    acc := BankAccount{Owner: "Alice", balance: 500.0}
    fmt.Println("Owner: ", acc.Owner)
    
    // Accessing 'balance' is allowed here because this code is in the same package (main).
    // If 'BankAccount' was imported from another package, accessing 'balance' would fail.
    fmt.Printf("Balance: %.2f\n", acc.balance)
}

3 Code Challenge

Challenge: Write a struct called `Product`. Declare one public field `Name` and one private field `cost`. Inside the package, write a method to initialize these fields and print details. Explain what happens when external packages try to read the `cost` property.