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In my solidity code, I am not using the global variable msg.* but still I get the error message in the function. Please explain why this function needs to be a Payable function

The below snippet is taken from https://github.com/imperialsoftech/coffee-supplychain-ethereum I just changed the compiler version to ^0.5.8 in truffle

enter image description here

/*get farm inspector data*/
function getFarmInspectorData(address batchNo) public onlyAuthCaller view returns (string memory coffeeFamily,
                                                                                   string memory typeOfSeed,
                                                                                   string memory fertilizerUsed){

    farmInspector memory tmpData = batchFarmInspector[batchNo];
    return (tmpData.coffeeFamily, tmpData.typeOfSeed, tmpData.fertilizerUsed);
}

Resolved..

modifier onlyAuthCaller() {
    lastAccess = msg.sender;   **<---------- this is the state variable getting updated.**
    require(
        authorizedCaller[msg.sender] == 1,
        "You are not authorized");
    _;
}
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I suspect this error message is misleading.

Try changing this:

farmInspector memory tmpData = batchFarmInspector[batchNo];

To this

farmInspector storage tmpData = batchFarmInspector[batchNo];

We can't see the whole picture, so I'm assuming batchFarmInspected is an array or a mapping of struct farmInspector. storage will make it a storage pointer and you should be able to return the three values, as expected.

See here for more details: https://blog.b9lab.com/storage-pointers-in-solidity-7dcfaa536089

Hope it helps.

  • mapping (address => farmInspector) batchFarmInspector; I tried to change like this farmInspector storage tmpData = batchFarmInspector[batchNo]; Still the same error.. The snippet is taken from github.com/imperialsoftech/coffee-supplychain-ethereum I just changed the compiler version to ^0.5.8 in truffle – iappmaker Jul 8 at 2:50
  • I understand that payable is used to access the global variable msg.* .. do we need that if we need to update the state variable ? – iappmaker Jul 8 at 2:59
  • No. Only msg.value. msg.sender is always available. – Rob Hitchens - B9lab Jul 8 at 4:52

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