Send Lumens and receive custom tokens in a single transaction?

Question

How do I implement the issuance of a loan with a pledge?

I want to send a loan from a multi-signature account and receive a pledge in the form of custom tokens in a single transaction.

At the moment I'm stuck in this place:

const transaction = new Stellar.TransactionBuilder(loan)
    .addOperation(Stellar.Operation.payment({
      destination: borrowerPublicKey,
      asset: Stellar.Asset.native(),
      amount
    }))
    .addOperation(... receive custom tokens)
    .build();

Answer 1

const transaction = new Stellar.TransactionBuilder(loan)
    .addOperation(Stellar.Operation.payment({
      destination: borrowerPublicKey,
      asset: Stellar.Asset.native(),
      amount
    }))
    .addOperation(Stellar.Operation.payment({
      destination: loan,
      asset: new Stellar.Asset('LOAN', loan),
      amount,
      source: borrowerPublicKey
    }))
    .build()

You'll need signatures from both the loan and borrowerPublicKey accounts, otherwise the transaction will fail. To achieve this you can prepare and sign a transaction with loan secret key on the server, and then request a signature from the borrower on the client side.