How to serialize and deserialize signed extrinsic?

[imstar15]

I want to enable users to sign extrinsic on the web page, and then send the signed extrinsic to the server, and let the server submit it to the chain.

The signed extrinsic can be toHex or toU8a, but I currently can't deserialize signedExtrinsic.

Here is my code:

const api = await getKusamaWeb3Api();
const extrinsic = await api.tx.crowdloan.contribute(
  parachainIndex,
  contributionValue,
  null  // signature: Option<MultiSignature>, default value: null
);

// Only sign and not send
const signedExtrinsic = await extrinsic.signAsync(kusamaAddress, { signer: injector.signer });
// signedExtrinsic's type is Submittable
console.log('signedExtrinsic: ', signedExtrinsic);

// Serialization
const extrinsicU8a = signedExtrinsic.toU8a();
console.log('extrinsicU8a: ', extrinsicU8a);

// Deserialization
const extrinsicB = new Extrinsic(api.registry, extrinsicU8a);
console.log('extrinsicB: ', extrinsicB);

Here is the console log:

signedExtrinsic:  Submittable {registry: TypeRegistry, createdAtHash: undefined, _raw: Map(2), __private_43_ignoreStatusCb: false, __private_44_transformResult: ƒ, …}
index.js?707a:96 extrinsicU8a:  Uint8Array(116) [201, 1, 132, 0, 56, 87, 177, 110, 95, 164, 213, 196, 234, 70, 3, 236, 233, 10, 30, 46, 138, 62, 96, 63, 177, 0, 171, 115, 224, 105, 49, 9, 250, 231, 163, 19, 1, 18, 214, 152, 60, 29, 155, 246, 93, 168, 175, 54, 39, 45, 0, 1, 14, 161, 246, 50, 191, 97, 223, 129, 89, 100, 211, 79, 109, 10, 248, 109, 123, 134, 28, 205, 208, 58, 14, 180, 25, 135, 179, 201, 48, 93, 165, 128, 150, 253, 27, 189, 199, 44, 135, 170, 254, 142, 12, 55, 158, 217, 240, 24, …]
index.js?707a:141 error:  Error: createType(Call):: findMetaCall: Unable to find Call with index 0xc901/[201,1]
    at createTypeUnsafe (createType.js?abb9:57)
    at TypeRegistry.createTypeUnsafe (registry.js?6fc9:338)
    at TypeRegistry.createType (registry.js?6fc9:330)
    at Function.decodeExtrinsic (Extrinsic.js?25bd:37)
    at new GenericExtrinsicV4 (Extrinsic.js?25bd:20)
    at _callee$ (index.js?707a:97)
    at tryCatch (runtime.js?df26:63)
    at Generator.invoke [as _invoke] (runtime.js?df26:293)
    at Generator.eval [as next] (runtime.js?df26:118)
    at asyncGeneratorStep (asyncToGenerator.js?4564:3)
    at _next (asyncToGenerator.js?4564:25)

What is the correct way to do it?

thanks!

[jacogr]

api.tx(<signed value>) returns it to a submittable (hex input here is ok)

[imstar15]

@jacogr Thanks

[polkadot-js-bot]

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