Methods और self

// Define a struct `Book` to group related fields together
struct Book {
    title: String,
    pages: u32,
}

// Implement methods on `Book`
impl Book {
    // Define the function `summary` taking `&self` and returning a String
    fn summary(&self) -> String {
        format!("{} ({} pages)", self.title, self.pages)
    }
}

// Entry point: execution of the program starts here
fn main() {
    // Declare an immutable variable `book`, set to `Book { title: String::from("The Rust Book"), pages: 500 }`
    let book = Book { title: String::from("The Rust Book"), pages: 500 };
    // Print "{}" to the console, substituting in `book.summary()` (with a trailing newline)
    println!("{}", book.summary());
}

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// Define a struct `Counter` to group related fields together
struct Counter {
    value: i32,
}

// Implement methods on `Counter`
impl Counter {
    // Define the function `increment` taking `self`
    fn increment(&mut self) {
        self.value += 1;
    }
}

// Entry point: execution of the program starts here
fn main() {
    // Declare a mutable variable `counter`, initialized to `Counter { value: 0 }`
    let mut counter = Counter { value: 0 };
    counter.increment();
    counter.increment();
    // Print "Counter: {}" to the console, substituting in `counter.value` (with a trailing newline)
    println!("Counter: {}", counter.value);
}

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// Define a struct `Wrapper` to group related fields together
struct Wrapper {
    value: String,
}

// Implement methods on `Wrapper`
impl Wrapper {
    // Define the function `unwrap` taking `self` and returning a String
    fn unwrap(self) -> String {
        self.value
    }
}

// Entry point: execution of the program starts here
fn main() {
    // Declare an immutable variable `wrapped`, set to `Wrapper { value: String::from("inside") }`
    let wrapped = Wrapper { value: String::from("inside") };
    // Declare an immutable variable `inner`, set to `wrapped.unwrap()`
    let inner = wrapped.unwrap();
    // Print "{}" to the console, substituting in `inner` (with a trailing newline)
    println!("{}", inner);
}

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// Define a struct `Temperature` to group related fields together
struct Temperature {
    celsius: f64,
}

// Implement methods on `Temperature`
impl Temperature {
    // Define the function `to_fahrenheit` taking `&self` and returning a floating-point number
    fn to_fahrenheit(&self) -> f64 {
        self.celsius * 9.0 / 5.0 + 32.0
    }
}

// Entry point: execution of the program starts here
fn main() {
    // Declare an immutable variable `temp`, set to `Temperature { celsius: 20.0 }`
    let temp = Temperature { celsius: 20.0 };
    // Print "{}F" to the console, substituting in `temp.to_fahrenheit()` (with a trailing newline)
    println!("{}F", temp.to_fahrenheit());
}

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