Solidity Function Call – Calling a Simple Function from Another Contract

contract-debuggingsolidity

I'm running into issues calling the function y() in the contract pullother. The input for the function y() is the output of the function g(). When I call y() using this input the output is blank ('' to be specific) rather than 15. I'm not exactly sure what I'm doing wrong here as this seems to align with the examples I see online of people successfully calling functions from other contracts.

The below is Untitled.sol

    pragma solidity ^0.4.6;

    contract helloworld {

    function f() returns (uint){
    return 15;
    }

    }

The below is the contract i would like to use to call the function f() in the contract helloworld.

pragma solidity ^0.4.6;

import "./Untitled.sol";

contract pullother {
address public hello;

function g() returns (address){
    hello = new helloworld();
    return hello;
}

function y(address contractadd) returns (uint){
    helloworld h = helloworld(contractadd);
    h.f();
}
}

Best Answer

I've tried your code in the solidity browser and it works

I think your need to use

return h.f()

Related Solutions

Solidity – VM Exception: Invalid JUMP When Calling a Second Function

You need to add the constant keyword to the test() function like:

pragma solidity ^0.4.0;
contract Test {
    mapping (address => uint256) weismap;

    function bet(uint vote) payable returns (uint256 weis) {
        if (msg.value==0) 
            throw;
        weismap[msg.sender]= msg.value;
        return  weismap[msg.sender];
    }

    function test() constant returns (uint myVote)  {
        return 1;
    }
}

Calling bet(...) with the value 2. Note that I'm sending 2 ethers as well with the transaction:

Now I call test() AND I've left the value 2. This call to test() fails as the constant function is being called as a transaction, not a read of the values off the blockchain:

If I call test() AND I've set value to blank, this call to test() succeeds as the constant function is being called as a read of the values off the blockchain:

Truffle Solidity – Solving Problem with Console: Cannot Read Property ‘Call’ of Undefined

If you are running the latest version of Truffle (v.3.x), the way to call a function or variable in your contract has evolved a little bit according to the Upgrading documentation

In Truffle 2.0, your contract abstractions managed your networks in a naive way, and added constructs like a "default network" that opened up the possibility of using the wrong network artifacts and deployed addresses at the wrong time. This provided a fancy and easy to use syntax – i.e., MyContract.deployed().myFunction(...) – but it left your code open to errors. Truffle 3.0 changes this syntax, where .deployed() is now thennable, like a promise (see example below). Similarly, this makes your contract abstractions seamlessly integrate with EIP 190, Ethereum's package management standard. All of this is for the better, but it means you'll have some changes to make all across the board.

So in your case, if you want to call a function, you have to do this:

HelloWorld.deployed().then(function(instance) {
    return instance.balance.call();
}).then(function(balance) {
    console.log(balance);
});

Please refer to the latest documentation for more details.

Best Answer

Related Solutions

Solidity – VM Exception: Invalid JUMP When Calling a Second Function

Truffle Solidity – Solving Problem with Console: Cannot Read Property ‘Call’ of Undefined

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