Public Method Types

Methods can be called externally by using the pub identifier within the #[near_bindgen] macro which will expose the method in the compiled WASM bytecode.

It is important to only mark methods that should be called externally as public. If you need a contract to call itself, you can mark the function as public but add the #[private] annotation so that it will panic if called from anything but the contract itself.

A basic usage of this would look like the following:

#[near_bindgen]
impl MyContractStructure {
    pub fn some_method(&mut self) {
        // .. method logic here
    }
}

Where this would expose some_method from the WASM binary and allow it to be called externally.

Expand to see generated code

#[cfg(target_arch = "wasm32")]
#[no_mangle]
pub extern "C" fn some_method() {
    near_sdk::env::setup_panic_hook();
    if near_sdk::env::attached_deposit() != 0 {
        near_sdk::env::panic("Method some_method doesn\'t accept deposit".as_bytes());
    }
    let mut contract: MyContractStructure = near_sdk::env::state_read().unwrap_or_default();
    contract.some_method();
    near_sdk::env::state_write(&contract);
}

Exposing trait implementations

Functions can also be exposed through trait implementations. This can be useful if implementing a shared interface or standard for a contract. This code generation is handled very similarly to basic pub functions, but the #[near_bindgen] macro only needs to be attached to the trait implementation, not the trait itself:

pub trait MyTrait {
    fn trait_method(&mut self);
}

#[near_bindgen]
impl MyTrait for MyContractStructure {
    fn trait_method(&mut self) {
        // .. method logic here
    }
}

In this example, the generated code will be the same as the previous example, except with a different method name.

Expand to see generated code

#[cfg(target_arch = "wasm32")]
#[no_mangle]
pub extern "C" fn trait_method() {
    near_sdk::env::setup_panic_hook();
    if near_sdk::env::attached_deposit() != 0 {
        near_sdk::env::panic("Method trait_method doesn\'t accept deposit".as_bytes());
    }
    let mut contract: MyContractStructure = near_sdk::env::state_read().unwrap_or_default();
    contract.trait_method();
    near_sdk::env::state_write(&contract);
}