How do you submit a pair when calling an entrypoint on a contract with Taquito?

Question

I am trying to submit a Pair of Bytes in a contract call with Taquito but am receiving an error.

The contract interaction documentation does not go into exactly how to submit a Pair, but it does go into how to access a Map with a Pair as a key.

Based on that I arrived at the following code, but am still receiving an error.

Contract has a single entrypoint, run_test, that accepts a Pair of Bytes, with the Bytes themselves being packed Strings.

This is the method used for packing the String (works fine when just sending Bytes instead of a Pair)

const packer = new MichelCodecPacker()
const packString = async stringData => {
  const packedString = await packer.packData({
    data: {
      string: stringData,
    },
    type: {
      prim: 'string',
    }
  })

  return packedString
}

used in the call

const leftByteData = await packString('Left String')
const rightByteData = await packString('Right String')

contract.methods.run_test(
    { 0: leftByteData.packed, 1: rightByteData.packed }
).send()

Which is accepting the type

TPair(TBytes, TBytes)

The error I receive is

BytesValidationError: [4] Invalid bytes: [object Object] at BytesToken.isValid
// ... verbose stack trace info snipped ...
at Array.map (<anonymous>) {
  value: {
    '0': '05010000000b4c65667420537472696e67',
    '1': '05010000000c526967687420537472696e67'
  },
  token: BytesToken {
    val: { prim: 'bytes' },
    idx: 4,
    fac: [Function: createToken],
    createToken: [Function: createToken]
  }
}

Is it possible to send a Pair as a value in a contract call with Taquito, and if so how do you do it?

Answer 1

Your code is correct, but you have to use the methodsObject property instead of methods if you want to use a JavaScript object as the parameter of the contract call.
Alternatively, you can split the elements of the pair and pass them separately to the contract call, like this:

contract.methods.run_test(leftByteData.packed, rightByteData.packed).send()

To learn more: https://tezostaquito.io/docs/smartcontracts/#choosing-between-the-methods-or-methodsobject-members-to-interact-with-smart-contracts