How to call a function and to read return values from an external deployed contract address?

Question

I am trying to call a function from deployed contract address using the below format

DeployedContractAddress.call(bytes4(keccak256("get(address)")),0xfffff);

But when trying to call the get(_address) using deployed contract address(without abi encoded), it should return an array. But here, it returns Boolean values true or false.

 function get(address _address) public returns (uint256[]){
 for(uint i=0;i<n;i++){
     arr[address].push(i);
 }
 return (arr);
}

Is there any simple way to get an array values without using ABI encoded?

Answer 1

According to the Solidity documentation, starting from version 0.5.0 it is possible to access the return data from a call:

address.call(bytes memory) returns (bool, bytes memory)

issue low-level CALL with the given payload, returns success condition and return data, forwards all available gas, adjustable

The data is given as a single bytes array, so you will likely want to decode it using abi.decode in order to make use of it.

Prior to version 0.5.0, you can count on the fact that the return values remains on the stack when the call() returns. They can be accessed, but you will have to use assembly.

Answer 2

The call method only returns a boolean value ( true / false ) based on the success it had calling said method.

If you want to read the "returned values" you need to deal with the ABI or you can do an assembly call and read and handle the values manually.

Check out How do I construct a call to another contract using inline assembly?

You can always specify an abstract interface for the abi you're going to use:

contract AbiInterface {
    function get(address _address) public returns (uint256[]);
}

function doIt() {
    AbiInterface myContract = AbiInterface.at(DeployedContractAddress);
    myContract.get(0xfffff);
}

But this of course does not work if you're trying to call arbitrary methods.