الإغلاقات

ما هي Closure؟

fn main() {
    let add_one = |x| x + 1;
    println!("{}", add_one(4));
}

صياغة Closure

fn main() {
    let multiply = |a, b| a * b;
    println!("{}", multiply(3, 5));
}

Closures متعددة الأسطر

fn main() {
    let describe = |n: i32| {
        let doubled = n * 2;
        println!("{} doubled is {}", n, doubled);
    };
    describe(7);
}

التقاط البيئة

fn main() {
    let factor = 10;
    let scale = |x| x * factor;
    println!("{}", scale(5));
}

استنتاج الأنواع في Closures

fn main() {
    let greet = |name: &str| -> String {
        format!("Hello, {}!", name)
    };
    println!("{}", greet("Rust"));
}

تمرير Closures كمعاملات

fn main() {
    let nums = vec![1, 2, 3];
    let doubled: Vec<i32> = nums.iter().map(|x| x * 2).collect();
    println!("{:?}", doubled);
}

التصفية باستخدام Closures

fn main() {
    let nums = vec![1, 2, 3, 4, 5, 6];
    let evens: Vec<i32> = nums.into_iter().filter(|x| x % 2 == 0).collect();
    println!("{:?}", evens);
}

تخزين Closures

fn main() {
    let is_even = |n: i32| n % 2 == 0;
    println!("{} {}", is_even(4), is_even(7));
}

Closures مقابل الدوال

fn main() {
    let base = 100;
    let bonus = |earned: i32| earned + base;
    println!("{}", bonus(25));
}

إعادة القيم المحسوبة

fn main() {
    let nums = vec![10, 20, 30];
    let total: i32 = nums.iter().map(|x| x + 1).sum();
    println!("total {}", total);
}

تلتقط Closures بالمرجع

fn main() {
    let name = String::from("Ada");
    let printer = || println!("Name: {}", name);
    printer();
    println!("still usable: {}", name);
}

تحقق سريع

مراجعة

fn main() {
    let tax = 0.2;
    let with_tax = |price: f64| price * (1.0 + tax);
    println!("{}", with_tax(50.0));
}