ride-1.scala

# In this example multiple accounts can deposit their funds and safely take them back.
# User balances are stored in the dApp state as mapping `address => waves`.

{-# STDLIB_VERSION 4 #-}
{-# CONTENT_TYPE DAPP #-}
{-# SCRIPT_TYPE ACCOUNT #-}

@Callable(i)
func deposit() = {
   # deposit function can be invoked from UI by user to top up the balance
   let pmt = extract(i.payment)  # creating variable with all data about a payment attached to the invokation
   if (isDefined(pmt.assetId)) then throw("can hodl waves only at the moment")  # waves-only threshold
   else {
        let currentKey = toBase58String(i.caller.bytes)  # determining caller key
        let currentAmount = match getInteger(this, currentKey) {  # reading current user's balance from the account state
            case a:Int => a
            case _ => 0  # taking zero as a balance value if this is the first time user deposits money
        }
        let newAmount = currentAmount + pmt.amount  # counting new balance as "old balance + payment value"
        [IntegerEntry(currentKey, newAmount)]  # updating user's balance in the account state
   }
}

@Verifier(tx)
func verify() = false  # this script can NOT be updated because of this verifier function