How do I validate the presence of participant owner in Asset transfer transaction

Question

In the "basic-sample-network" or "trade-network" or "marbles-demo" sample of Hyperledger Fabric Composer - once the transaction is submitted then it checks for the presence of the asset ID in the database. However, it does not check if the new owner (participant) is actually present. How to check that the new owner is actually present in the database created?

Answer 1

I found the exact solution and syntax.. This is for the marbles trading demo and it checks for presence of both participant and the asset

/**
  * Trade a marble to a new player
  * @param {org.hyperledger_composer.marbles.TradeMarble} tradeMarble - the trade marble transaction
  * @transaction
  */
 function tradeMarble(tradeMarble) {
   return getParticipantRegistry('org.hyperledger_composer.marbles.Player')
     .then(function(playerRegistry) {
       return playerRegistry.exists(tradeMarble.newOwner.getIdentifier())
     })
      .then(function(exists) {
       if(!exists) {
         throw Error('Invalid participant id')
       } else {
        return getAssetRegistry('org.hyperledger_composer.marbles.Marble')
         .then(function (assetRegistry) {
          tradeMarble.marble.owner = tradeMarble.newOwner;
          return assetRegistry.update(tradeMarble.marble);
      });
       }
     })
 }