gistfile1.txt

/* This works ---------------------------- 

NB: shell variables are replaced with their
    values before 'uplink_create_contract'
    is called.

*/ 

global account david = u'${DAVID_ADDRESS}';
global account charlie = u'${CHARLIE_ADDRESS}';

global assetDisc usd = a'${USD_ASSET_ADDRESS}';
global assetDisc assetAddress = a'${VIOLIN_ADDRESS}';

global int usdAmount;
global int numTokens;

transition initial -> loop;
transition loop -> loop;
transition loop -> terminal;

@initial {david}
start() {
  transitionTo(:loop);
}

@loop {charlie}
execute(int usdValue, int tokenAmount) {
  usdAmount = usdValue;
  transferTo(usd, usdAmount);

  numTokens = tokenAmount;
  transferHoldings(david, assetAddress, numTokens, charlie);

  transferFrom(usd, usdAmount, david);

  transitionTo(:loop);
}

@loop {david}
terminate() {
  transitionTo(:terminal);
}

### Given the contract above, I can call it like this to swap
### one violin token for one USD cent;

  result = rpc.uplink_call_contract(
          private_key = privkey,
          from_address = account_address,
          contract_addr = contract_address,
          method = 'execute',
          args = [VInt(1), VInt(1)]
          )

### I want to pass in the asset, buyer and seller addresses,
### so to try and pass in the asset address, I modified the
### contract like this;


global account david = u'${DAVID_ADDRESS}';
global account charlie = u'${CHARLIE_ADDRESS}';

global assetDisc usd = a'${USD_ASSET_ADDRESS}';
global assetDisc assetAddress;

global int usdAmount;
global int numTokens;

transition initial -> loop;
transition loop -> loop;
transition loop -> terminal;

@initial {david}
start() {
  transitionTo(:loop);
}

@loop {charlie}
execute(int usdValue, assetDisc astAddr, int tokenAmount) {
  usdAmount = usdValue;
  transferTo(usd, usdAmount);

  assetAddress = astAddr;
  numTokens = tokenAmount;
  transferHoldings(david, assetAddress, numTokens, charlie);

  transferFrom(usd, usdAmount, david);

  transitionTo(:loop);
}

@loop {david}
terminate() {
  transitionTo(:terminal);
}


### Then tried to call it like this;

result = rpc.uplink_call_contract(
        private_key = privkey,
        from_address = account_address,
        contract_addr = contract_address,
        method = 'execute',
        args = [VInt(1), VAsset(asset_address), VInt(1)]
        )

### The call fails, and in the logs I can see this error;

[2018-09-08T11:38:58.950+00:00] (Messaging) Could not verify transaction with signature: Base64PByteString {unbase64P = "AE0zMDE5NjQ3ODI5ODI1Nzg1MTczNjQ4OTY3NDI3NjAxNzY5MzcxMDE5MTMzOTcxNDc3NjI3MjczNDkzOTgyNTg0MTc2OTQyNDIxODExNToATTgzMTg2ODM5OTA3MTE2OTQzMDYyNjk5Mjk1MjM4MzU3Njk0MjQzNTMwODA3ODE0NDk5OTg2NzA0OTIyNzc2MDEyODc2Nzc1ODk3NTc4"} due to: InvalidTransaction {transaction = Transaction {header = TxContract (Call {address = Address "5naLArqVf6yoFjLHJg2wQPQRoFaehSHiqg4qgYrb56Ya", method = "execute", args = [VInt 1,VAsset (Address "3D76xmFJffT4CyRx8vcypj3yKHoTLvPwKP9sk5gaShkX"),VInt 1]}), signature = Base64PByteString {unbase64P = "AE0zMDE5NjQ3ODI5ODI1Nzg1MTczNjQ4OTY3NDI3NjAxNzY5MzcxMDE5MTMzOTcxNDc3NjI3MjczNDkzOTgyNTg0MTc2OTQyNDIxODExNToATTgzMTg2ODM5OTA3MTE2OTQzMDYyNjk5Mjk1MjM4MzU3Njk0MjQzNTMwODA3ODE0NDk5OTg2NzA0OTIyNzc2MDEyODc2Nzc1ODk3NTc4"}, origin = Address "2PeARE8xv4w2PTqrhPd3ag1b41FnbQRoVCXvWd5tDE4C"}, reason = InvalidTxField (InvalidTxSignature (InvalidSignature (Signature {sign_r = 30196478298257851736489674276017693710191339714776272734939825841769424218115, sign_s = 83186839907116943062699295238357694243530807814499986704922776012876775897578}) "\NUL\NUL\NUL\STXG\ESC\146\&0M9\v[O\219\219\165V\187\176\250O\SUB\219\NAK\151\188\131\f\134sU\b\141\156\246{\NUL\NUL\NUL\NUL\NUL\NUL\NUL\aexecute\NUL\NUL\NUL\NUL\NUL\NUL\NUL\ETX\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\SOH\ACK \209>v\211MH\r\239Ll7W(\192\ESC\155u\ESC\SUB>\CAN\186\219\254\255D\n\175\&3FT\NUL\NUL\NUL\NUL\NUL\NUL\NUL\NUL\SOH"))}