Build on Flow | Learn FCL – 9. How to pass Optional and Path Arguments to Scripts

// Import methods from FCL
import { query, config } from "@onflow/fcl";

// Specify the API endpoint - this time we will use Mainnet
const api = "https://rest-mainnet.onflow.org";

// Configure FCL to use mainnet as the access node
config().put("accessNode.api", api);

// Path Arguments
const passPathArgument = async () => {
  const cadence = `
    pub fun main(public: PublicPath, private: PrivatePath, storage: StoragePath): PrivatePath{
      // we can return any value, but let's return one of the Paths to see
      // how FCL decodes it into value
      return private
    }
  `;

  // Since we are not gonna use any of those for actual data access
  // we can construct any paths we like
  // this one will encode "/public/flowTokenVault"
  const publicPath = {
    domain: "public",
    identifier: "flowTokenVault"
  };

  // encode "/private/flowTokenVault"
  const privatePath = {
    domain: "private",
    identifier: "flowTokenVault"
  };

  // encode "/storage/flowTokenVault"
  const storagePath = {
    domain: "storage",
    identifier: "flowTokenVault"
  };

  // Notice that t.Path is not a function, but a constant!
  const args = (arg, t) => [
    arg(publicPath, t.Path),
    arg(privatePath, t.Path),
    arg(storagePath, t.Path)
  ];
  const result = await query({ cadence, args });
  console.log({ result });
};

// Optionals
const passOptionalIntegers = async () => {
  const cadence = `
    pub fun main(a: Int?): Int?{
      return a
    }
  `;

  // We will set value of our Int argument to null to check that script works correctly
  const a = null;
  const args = (arg, t) => [arg(a, t.Optional(t.Int))];

  const result = await query({ cadence, args });
  console.log({ result });
}; 

const passMultiOptional = async () => {
  const cadence = `
    pub fun main(a: String?, b: Bool?, c: UFix64?, d: Address?): Address?{
      return d
    }
  `;

    // it's perfectly fine to pass non-nil values alongside "empty"
  const a = "Hello";
  const b = null;
  const c = null;
  const d = "0x01";

  // Note the types are the same as we specify in Cadence code
  const args = (arg, t) => [
    arg(a, t.Optional(t.String)),
    arg(b, t.Optional(t.Bool)),
    arg(c, t.Optional(t.UFix64)),
    arg(d, t.Optional(t.Address))
  ];

  const result = await query({ cadence, args });
  console.log({ result });

  showResult("multiple", result);
};

const passArrayOfOptinalStrings = async () => {
  const cadence = `
    pub fun main(a: [String?]): String?{
      return a[0]
    }
  `;

  const a = ["Hello", null];
  // Type of the argument is composed of t.Array, t.Optional and t.String
  const args = (arg, t) => [arg(a, t.Array(t.Optional(t.String)))];
  const result = await query({ cadence, args });
  console.log({ result }); //
};

const passOptionalArray = async () => {
  const cadence = `
    pub fun main(a: [String]?): String?{
      if let arr = a {
        return arr[0]
      }

      return nil
    }
  `;
  const a = null;
  // This time we will wrap our array in "t.Optional()" call
  const args = (arg, t) => [arg(a, t.Optional(t.Array(t.String)))];
  const optionalArray = await query({ cadence, args });
  console.log({ optionalArray }); //
};

const passDictionaryOfOptionals = async () => {
  // In this example we will pass a Cadence Dictionary as argument
  // keys will be of type "String" and values will be Optionals of type "Int?"
  const cadence = `
    pub fun main(a: {String: Int?}): Int??{
      return a["amount"]
    }
  `;

  // Dictionaries should be represented as array of key/value pairs of respective types
  // Note that we shall pass numeric value as string here
  const a = [{ key: "amount", value: "42" }];
  // Dictionary type is composed out of t.Dictionary, t.String and t.Int for our case
  const args = (arg, t) => [
    arg(a, t.Dictionary({ key: t.String, value: t.Optional(t.Int) }))
  ];

  const result = await query({ cadence, args });
  console.log({ result });
};

(async () => {
    console.clear();

    // Path arguments
  await passPathArgument();

    // Optional arguments
  await passOptionalIntegers();
  await passMultiOptional();
  await passArrayOfOptinalStrings();
  await passOptionalArray();
  await passDictionaryOfOptionals();
})();

{result: Object}
    result: {
        domain: "private",
        identifier: "flowTokenVault"
    }
{result: null}
{result: "0x0000000000000001"}
{result: "Hello"}
{optionalArray: null}
{result: "42"}