Impl & Methods

In Flame, methods and associated functions are defined within impl blocks attached to a struct or enum.

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Defining an impl Block

struct Account {
    owner: String,
    balance: Float
}

impl Account {
    // 1. Associated Function / Constructor (No self parameter)
    fn new(owner: String, initial_deposit: Float) -> Account {
        return Account {
            owner: owner,
            balance: initial_deposit
        }
    }

    // 2. Immutable Method (Borrows self immutably: &self)
    fn get_balance(&self) -> Float {
        return self.balance
    }

    // 3. Mutable Method (Borrows self mutably: &mut self)
    fn deposit(&mut self, amount: Float) {
        self.balance = self.balance + amount
    }

    // 4. Value Method (Consumes/Moves self: self)
    fn close(self) -> Float {
        print($"Closing account for {self.owner}")
        return self.balance
    }
}

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Method Receiver Types

Flame strictly distinguishes method receiver types according to ownership rules:

Receiver	Syntax	Semantics
Associated Function	fn name(...)	Called on the type itself: Account.new(...)
Immutable Borrow	fn name(&self)	Reads data from instance without modifying or consuming it
Mutable Borrow	fn name(&mut self)	Can modify instance fields in-place
Consuming Move	fn name(self)	Takes ownership of instance; variable cannot be used afterwards

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Usage Example

// Call constructor
let mut my_acc = Account.new("Alice", 500.0)

// Call immutable method
print($"Current Balance: {my_acc.get_balance()}") // 500.0

// Call mutable method
my_acc.deposit(250.0)
print($"Updated Balance: {my_acc.get_balance()}") // 750.0

// Call consuming method (moves `my_acc`)
let payout = my_acc.close()
print($"Final payout: {payout}")

// print(my_acc.get_balance()) // Error: `my_acc` was moved by `.close()`!