Payable Methods

We can allow methods to accept token transfer together with the function call. This is done so that contracts can define a fee in tokens that needs to be payed when they are used. By the default the methods are not payable and they will panic if someone will attempt to transfer tokens to them during the invocation. This is done for safety reason, in case someone accidentally transfers tokens during the function call.

To declare a method as payable, use the #[payable] annotation within the near_bindgen macro as follows:

#[payable]
pub fn my_method(&mut self) {
...
}

This will allow the my_method function to be called and transfer balance to the contract.

Example:

#[near_bindgen]
impl Contract {
    #[payable]
    pub fn take_my_money(&mut self) {
        env::log_str("Thanks!");
    }
    pub fn do_not_take_my_money(&mut self) {
        env::log_str("Thanks!");
    }
}

is equivalent to:

#[near_bindgen]
impl Contract {
    pub fn take_my_money(&mut self) {
        env::log_str("Thanks!");
    }
    pub fn do_not_take_my_money(&mut self) {
        if near_sdk::env::attached_deposit() != 0 {
            near_sdk::env::panic(b"Method do_not_take_my_money doesn't accept deposit");
        }
        env::log_str("Thanks!");
    }
}