Contract calls & match

Reading state from a contract can revert. In hand-written AssemblyScript an unguarded call aborts the whole handler; the idiomatic fix (try_*) is easy to forget. Redstart makes the safe path the only path: a contract call returns a Result, and you must match it before touching the value.

handler on Token.Approval(event) {
  let result = ERC20.bind(event.address).balanceOf(event.params.owner)
  match result {
    Ok(currentBalance) => {
      let owner = Account.loadOrCreate(event.params.owner, { balance: BigInt.zero })
      owner.balance = currentBalance
    }
    Err(e) => {
      // call reverted — leave balances untouched
    }
  }
}

This lowers to graph-ts’s try_balanceOf() and a .reverted check — the correct pattern, generated for you. Accessing .value without a surrounding match is a compile error (E…: .value-without-match).

Binding

ERC20.bind(address) produces a typed contract instance. Every function in the imported ABI is available, with ABI-typed parameters and return values.