Why is this cross-contract call misbehaving?

Question

#[ink(message)]
        pub fn create_new_better_payment(
            &mut self,
            _value: Balance,
            _arbiter_provider: AccountId,
            _deadline: u64,
            //this deadline is deadline that will be added to current time once the audit is assigned to an auditor.
        ) -> Result<()> {
            let _now = self.env().block_timestamp();
            let x = PaymentInfo {
                value: _value,
                starttime: _now,
                auditor: self.env().caller(),
                arbiterprovider: _arbiter_provider,
                patron: self.env().caller(),
                deadline: _deadline,
                currentstatus: AuditStatus::AuditCreated,
            };
            assert_ne!(_value, 0);
            let xyz = ink::env::call::build_call::<Environment>()
                .call(self.stablecoin_address)
                .gas_limit(0)
                .exec_input(
                    ink::env::call::ExecutionInput::new(ink::env::call::Selector::new(
                        ink::selector_bytes!("transfer_from"),
                    ))
                    .push_arg(self.env().caller())
                    .push_arg(self.env().account_id())
                    .push_arg(_value),
                )
                .returns::<bool>()
                .invoke();
            if xyz {
                self.env().emit_event(TokenIncoming {
                    id: self.current_audit_id,
                });
                self.audit_id_to_payment_info
                    .insert(&self.current_audit_id, &x);
                self.env().emit_event(AuditInfoUpdated {
                    id: Some(self.current_audit_id),
                    payment_info: Some(x),
                    updated_by: Some(self.env().caller()),
                });
                self.current_audit_id = self.current_audit_id + 1;
                return Ok(());
            } else {
                return Err(Error::InsufficientBalance);
            }
        }

Why is this function misbehaving?

I am trying to send the caller's ERC20 tokens to this contract in the above function, The rest of everything is working, but not the cross-contract calling.

What am I doing wrong here? This function will update the state of its contract but won't transfer the ERC20 tokens of other contract.

Answer 1

You need to call approve before transfer_from. Most likely ERC20 contract returned an error. You need to handle errors from the cross contract call.

See more about error handling here and here