Struct ExampleContract 

pub struct ExampleContract;

Neo N3 Contract Examples

Basic Hello-World pattern showing how to expose a method that simply returns contract state. This shows canonical devpack syntax for contract methods and metadata:

use neo_devpack::prelude::*;

#[neo_contract]
pub struct HelloWorld {
    greeting: NeoString,
}

impl HelloWorld {
    #[neo_method]
    pub fn say_hello(&self) -> NeoResult<NeoString> {
        Ok(self.greeting.clone())
    }
}

A more complete storage-backed counter that demonstrates manifest overlays, permissions, witnesses and event emission:

use neo_devpack::prelude::*;

#[neo_event]
pub struct CounterIncreased {
    pub account: NeoByteString,
    pub new_value: NeoInteger,
}

neo_manifest_overlay!(r#"{
    "name": "FamousCounter",
    "features": { "storage": true }
}"#);
neo_permission!("*", ["balanceOf"]);
neo_supported_standards!(["NEP-17"]);

#[neo_contract]
pub struct FamousCounter;

impl FamousCounter {
    #[neo_method]
    pub fn increment(&self, caller: NeoByteString) -> NeoResult<NeoInteger> {
        if !NeoRuntime::check_witness(&caller)?.as_bool() {
            return Err(NeoError::InvalidOperation);
        }

        let context = NeoStorage::get_context()?;
        let counter_key = NeoByteString::from_slice(b"counter");
        NeoStorage::put(&context, &counter_key, &NeoByteString::from_slice(b"1"))?;

        CounterIncreased {
            account: caller.clone(),
            new_value: NeoInteger::new(1),
        }
        .emit()?;

        Ok(NeoInteger::new(1))
    }
}