Drop Trait का उपयोग

// Define a struct `Logger` to group related fields together
struct Logger {
    name: String,
}

// Implement the `Drop` trait for `Logger`
impl Drop for Logger {
    // Define the function `drop` taking `self`
    fn drop(&mut self) {
        // Print "Logger '{}' shutting down" to the console, substituting in `self.name` (with a trailing newline)
        println!("Logger '{}' shutting down", self.name);
    }
}

// Entry point: execution of the program starts here
fn main() {
    // Declare an immutable variable `_logger`, set to `Logger { name: String::from("main-logger") }`
    let _logger = Logger { name: String::from("main-logger") };
    // Print "Logger is active" to the console (with a trailing newline)
    println!("Logger is active");
}

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// Define a struct `Resource` to group related fields together
struct Resource;

// Implement the `Drop` trait for `Resource`
impl Drop for Resource {
    // Define the function `drop` taking `self`
    fn drop(&mut self) {
        // Print "Resource cleaned up" to the console (with a trailing newline)
        println!("Resource cleaned up");
    }
}

// Entry point: execution of the program starts here
fn main() {
    // Declare an immutable variable `res`, set to `Resource`
    let res = Resource;
    // Print "About to drop early" to the console (with a trailing newline)
    println!("About to drop early");
    drop(res);
    // Print "Dropped; continuing" to the console (with a trailing newline)
    println!("Dropped; continuing");
}

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// Define a struct `Item` to group related fields together
struct Item(i32);

// Implement the `Drop` trait for `Item`
impl Drop for Item {
    // Define the function `drop` taking `self`
    fn drop(&mut self) {
        // Print "Dropping item {}" to the console, substituting in `self.0` (with a trailing newline)
        println!("Dropping item {}", self.0);
    }
}

// Entry point: execution of the program starts here
fn main() {
    // Declare an immutable variable `_a`, set to `Item(1)`
    let _a = Item(1);
    // Declare an immutable variable `_b`, set to `Item(2)`
    let _b = Item(2);
    // Declare an immutable variable `_c`, set to `Item(3)`
    let _c = Item(3);
    // Print "All items created" to the console (with a trailing newline)
    println!("All items created");
}

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// Define a struct `Connection` to group related fields together
struct Connection {
    id: u32,
}

// Implement the `Drop` trait for `Connection`
impl Drop for Connection {
    // Define the function `drop` taking `self`
    fn drop(&mut self) {
        // Print "Closing connection #{}" to the console, substituting in `self.id` (with a trailing newline)
        println!("Closing connection #{}", self.id);
    }
}

// Define the function `use_connection` with no parameters
fn use_connection() {
    // Declare an immutable variable `_conn`, set to `Connection { id: 7 }`
    let _conn = Connection { id: 7 };
    // Print "Using connection #7" to the console (with a trailing newline)
    println!("Using connection #7");
}

// Entry point: execution of the program starts here
fn main() {
    use_connection();
    // Print "Connection was closed automatically" to the console (with a trailing newline)
    println!("Connection was closed automatically");
}

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