pub
- Rust course
- Intermediate
- Lesson 73/115
- 4 min
Control visibility with pub.
pub
Visibility is decided item by item. For a struct, pub only opens the type; each field must be marked separately. For an enum, pub opens all variants:
mod banka {
pub struct Hesap {
pub sahip: String, // readable/writable from outside
bakiye: i64, // private
}
pub enum Tur { Vadesiz, Vadeli } // both variants are open
}A struct with a private field can't be built from outside with Hesap { .. }; a constructor (pub fn new) must be offered.
Getter and constructor
Controlled access to private fields is given through methods:
impl Hesap {
pub fn new(sahip: &str) -> Self {
Self { sahip: sahip.to_string(), bakiye: 0 }
}
pub fn bakiye(&self) -> i64 {
self.bakiye
}
pub fn yatir(&mut self, n: i64) {
if n > 0 {
self.bakiye += n;
}
}
}Code inside the module can always access private fields in the same module.
Practice Bank module
Inside mod banka, write Hesap with a pub sahip field and a private bakiye field; add the methods new, bakiye and yatir. In main, open an account for "Ece" and deposit 50; print h.sahip and h.bakiye() separated by a space.
Starter code
fn main() {
// buraya yaz
}Sample solution
mod banka {
pub struct Hesap {
pub sahip: String,
bakiye: i64,
}
impl Hesap {
pub fn new(sahip: &str) -> Self {
Self {
sahip: sahip.to_string(),
bakiye: 0,
}
}
pub fn bakiye(&self) -> i64 {
self.bakiye
}
pub fn yatir(&mut self, n: i64) {
if n > 0 {
self.bakiye += n;
}
}
}
}
use banka::Hesap;
fn main() {
let mut h = Hesap::new("Ece");
h.yatir(50);
println!("{} {}", h.sahip, h.bakiye());
}Expected output
Ece 50
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 What is the benefit of keeping the balance private?
- The balance can only change through methods following the rules (yatir, cek) Correct answer
- It runs faster
- Memory saving
- The compiler requires it
Explanation: Encapsulation protects invariants: for example, the balance never goes negative.
2 Public field
pub struct Hesap {
____ sahip: String,
bakiye: i64,
}pub struct Hesap {
pub sahip: String,
bakiye: i64,
}Explanation: Struct fields are opened individually with pub.
3 Item and outside access
| Term | Meaning |
|---|---|
pub sahip |
Readable and writable |
bakiye (no pub) |
Inaccessible |
pub enum Tur |
All variants open |
pub fn bakiye(&self) |
Read-only access |