The following is a simple example of a contract which implements a counter. Both the initialize_counter() and increment_counter() ABI methods return the currently set value.
forc template --template-name counter my_counter_projectcontract;
abi TestContract {
#[storage(write)]
fn initialize_counter(value: u64) -> u64;
#[storage(read, write)]
fn increment_counter(amount: u64) -> u64;
}
storage {
counter: u64 = 0,
}
impl TestContract for Contract {
#[storage(write)]
fn initialize_counter(value: u64) -> u64 {
storage.counter.write(value);
value
}
#[storage(read, write)]
fn increment_counter(amount: u64) -> u64 {
let incremented = storage.counter.read() + amount;
storage.counter.write(incremented);
incremented
}
}