Learn INK with Real Code Examples

#[ink::contract]
mod counter {
    #[ink(storage)]
    pub struct Counter {
        value: u64,
    }

    impl Counter {
        #[ink(constructor)]
        pub fn new() -> Self {
        Self { value: 0 }
        }

        #[ink(message)]
        pub fn increment(&mut self) {
        self.value += 1;
        }

        #[ink(message)]
        pub fn reset(&mut self) {
        self.value = 0;
        }
    }
}

A minimal Ink! contract defining a counter with increment and reset functions.

#[ink::contract]
mod owner_message {
    #[ink(storage)]
    pub struct OwnerMessage {
        owner: AccountId,
        message: ink::prelude::string::String,
    }

    impl OwnerMessage {
        #[ink(constructor)]
        pub fn new() -> Self {
        Self {
        owner: Self::env().caller(),
        message: String::from(""),
        }
        }

        #[ink(message)]
        pub fn set_message(&mut self, msg: String) {
        assert!(self.env().caller() == self.owner);
        self.message = msg;
        }
    }
}

A contract where only the owner can update a stored message.

#[ink::contract]
mod token {
    #[ink(storage)]
    pub struct Token {
        total: u64,
        balances: ink::storage::Mapping<AccountId, u64>,
    }

    impl Token {
        #[ink(constructor)]
        pub fn new(amount: u64) -> Self {
        let caller = Self::env().caller();
        let mut balances = ink::storage::Mapping::new();
        balances.insert(caller, &amount);
        Self { total: amount, balances }
        }

        #[ink(message)]
        pub fn transfer(&mut self, to: AccountId, amount: u64) {
        let caller = self.env().caller();
        let caller_balance = self.balances.get(caller).unwrap_or(0);
        assert!(caller_balance >= amount);
        self.balances.insert(caller, &(caller_balance - amount));
        let to_balance = self.balances.get(to).unwrap_or(0);
        self.balances.insert(to, &(to_balance + amount));
        }
    }
}

A basic ERC20-like token implementation in Ink! supporting mint, transfer, and balance queries.

#[ink::contract]
mod vault {
    #[ink(storage)]
    pub struct Vault {}

    impl Vault {
        #[ink(constructor)]
        pub fn new() -> Self { Self {} }

        #[ink(message, payable)]
        pub fn deposit(&mut self) {}

        #[ink(message)]
        pub fn withdraw(&mut self, amount: u128) {
        self.env().transfer(self.env().caller(), amount).unwrap();
        }
    }
}

A vault contract for storing native chain tokens with deposit/withdraw logic.

#[ink::contract]
mod timelock {
    #[ink(storage)]
    pub struct Timelock {
        unlock: u64,
    }

    impl Timelock {
        #[ink(constructor)]
        pub fn new(unlock: u64) -> Self { Self { unlock } }

        #[ink(message)]
        pub fn withdraw(&mut self) {
        assert!(self.env().block_timestamp() >= self.unlock);
        self.env().transfer(self.env().caller(), self.env().balance()).unwrap();
        }
    }
}

Funds can be withdrawn only after a specific block timestamp.

#[ink::contract]
mod voting {
    #[ink(storage)]
    pub struct Voting {
        yes: u64,
        no: u64,
    }

    impl Voting {
        #[ink(constructor)]
        pub fn new() -> Self { Self { yes: 0, no: 0 } }

        #[ink(message)]
        pub fn vote(&mut self, choice: bool) {
        if choice { self.yes += 1; } else { self.no += 1; }
        }
    }
}

A minimal yes/no voting system implemented in Ink!.

#[ink::contract]
mod whitelist {
    #[ink(storage)]
    pub struct Whitelist {
        owner: AccountId,
        allowed: ink::storage::Mapping<AccountId, bool>,
    }

    impl Whitelist {
        #[ink(constructor)]
        pub fn new() -> Self {
        Self { owner: Self::env().caller(), allowed: ink::storage::Mapping::new() }
        }

        #[ink(message)]
        pub fn add(&mut self, user: AccountId) {
        assert!(self.env().caller() == self.owner);
        self.allowed.insert(user, &true);
        }

        #[ink(message)]
        pub fn restricted(&self) {
        assert!(self.allowed.get(self.env().caller()).unwrap_or(false));
        }
    }
}

Only whitelisted users can perform a restricted action.

#[ink::contract]
mod logger {
    #[ink(event)]
    pub struct Log {
        #[ink(topic)]
        from: AccountId,
        msg: String,
    }

    #[ink(storage)]
    pub struct Logger {}

    impl Logger {
        #[ink(constructor)]
        pub fn new() -> Self { Self {} }

        #[ink(message)]
        pub fn fire(&self, msg: String) {
        self.env().emit_event(Log { from: self.env().caller(), msg });
        }
    }
}

Demonstrates Ink! events with a simple log message.

#[ink::contract]
mod config {
    #[ink(storage)]
    pub struct Config {
        config: u64,
    }

    impl Config {
        #[ink(constructor)]
        pub fn new(num: u64) -> Self {
        Self { config: num }
        }

        #[ink(message)]
        pub fn get(&self) -> u64 { self.config }
    }
}

Shows how to use immutable data in Ink!.

#[ink::contract]
mod multiplier {
    #[ink(storage)]
    pub struct Multiplier {
        factor: u64,
    }

    impl Multiplier {
        #[ink(constructor)]
        pub fn new(f: u64) -> Self {
        Self { factor: f }
        }

        #[ink(message)]
        pub fn multiply(&self, x: u64) -> u64 {
        x * self.factor
        }
    }
}

Multiplies any input by a stored factor.