Reading contract value returns null

Question

Facing an issue while trying to query for a value in my contract. The value keeps getting retuned as null with an error. However, it works fine on substrate Contracts UI

Front end Dapp :

  const gasLimit = 3000n * 1000000n;
  // a limit to how much Balance to be used to pay for the storage created by the contract call
  // if null is passed, unlimited balance can be used
  const storageDepositLimit = null

  // Load the contract instance
  const Contract = new ContractPromise(api, abi, AlephsendContractAddress);
 
    // Perform a read of the contract's `get` message
  const callValue = await Contract.query.isPause("5HGn5UF5qdz8ShagwxRFSm387Hhd4wccAuVHZ17KtyyeUone",{
    gasLimit,
    storageDepositLimit,
  });
  console.log(callValue.output.toHuman());

Contract function :

#[ink(message)]
pub fn is_pause(&self) -> bool {
   
   return self.paused;
   
}

This is how my storage is defined :

#![cfg_attr(not(feature = "std"), no_std, no_main)]

#[ink::contract]

mod aleph_send {

use openbrush::contracts::traits::psp22::{PSP22Ref,PSP22Error};
use openbrush::contracts::ownable::*;
use scale::alloc::vec::Vec;
use openbrush::traits::Storage;


#[ink(storage)]
#[derive(Default, Storage)]
pub struct Aleph {
    #[storage_field]
        ownable: ownable::Data,
        pub fee    : Balance,
        pub paused : bool
}



impl Aleph {...contract code}

Any help would be much appreciated!

Answer 1

I can't see what is wrong with your call, but let's try to fix it.

First be sure you have the proper metadata, see this previous StackExchange issue: How can you query a smart contract using the polkadot.js api?

You can try too if the result of the query has been ok like this:

const { result, output } = await Contract.query.isPause("5HGn5UF5qdz8ShagwxRFSm387Hhd4wccAuVHZ17KtyyeUone",{
    gasLimit,
    storageDepositLimit,
});
// check if the call was successful
if (result.isOk) {
  // output the return value
  console.log('Success', output.toHuman());
} else {
  console.error('Error', result.asErr);
}

You have an example here: Reading contract values where it queries the incrementer smart contract.

And similar in this previous StackExchange Issue: How to get output when calling a contract method and signing it?

Answer 2

gasLimit should be of type WeighV2, not Weight. Try something like

const gasLimit = api.registry.createType(
  'WeightV2',
  api.consts.system.blockWeights['maxBlock']
) as WeightV2;

For querying a method this should be sufficient. If you want to execute transactions than you need to query a method first to get gas limits.