Accessing Mapping from Another Contract

Question

I wanted to access (update/get) data from a mapping in another contract. Is it possible to access the mapping variables without writing a function to read/write. I looked at (here) but still little unclear on the approach.

I am getting an error "Indexed expression has to be a type, mapping, array at the line - "myData.contractsMap[_name].push(_value)"

Any suggestions? Thanks,

pragma solidity ^0.4.15;

contract Data {

    mapping (bytes32 => uint[])  public contractsMap;

}

contract ContractCreator {

    Data myData;
    uint[] myValueList;

    event Log(bytes32, uint);

    function ContractCreator() public {

        myData = new Data();
    }

    function setElements (bytes32 _name, uint _value) public {

        myData.contractsMap[_name].push(_value); //ERROR
    }

    function getElements (bytes32 _name) public {

       myValueList = myData.contractsMap[_name];
       for (uint i = 0; i < myValueList.length; i++) {
           Log(_name, myValueList[i]);
       }
    }
}

Answer 1

Sorry, but you are currently not allowed to access mappings of type (bytes32 => uint[]) in other contracts. You have to create the getters/setters in your Data contract and modify/access the mappings through these getters/setters in your ContractCreator contract.

Answer 2

mappings are private by default. like the poster above said, you'll need to have setters and getters in order for it to be accessible.

contract ContractFoo {
  mapping (address=>uint) somemapping; //not accessible unless there is a getter

  function getMapping(address _address) public constant returns (uint) {
    return somemapping[addr]
  }
}

here's a fiddle: https://ethfiddle.com/D0H5CVFT1B