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I was trying to access and store a Struct from an external contract. Is there a way with which this is possible. This would be a simple PoC where I am trying to access a Struct from Student contract in ClassRoom Contract but keep getting:

TypeError: Type tuple(string memory,uint256,bool) is not implicitly convertible to expected type struct stu storage ref.
  --> contracts/TestContract.sol:32:16:
   |
32 |         test = student.studentNames(ID);
   |     

Contracts:

SPDX-License-Identifier: MIT
pragma solidity ^0.8.0;
struct stu {
    string name;
    uint age;
    bool tookTest;
}
contract Student{
    mapping(uint => stu) public studentNames;
    function addStudent (uint ID, string memory _name, uint _age) public {
        studentNames[ID] = stu(_name, _age, false);
    }
    function updateStudent (uint ID) public {
        studentNames[ID].tookTest = true;
    }
}
contract ClassRoom {
    address studentAddr;
    Student student;
    stu public test;
    function classRoom(address addr) public {
        studentAddr = addr;
        student = Student(addr);
    }

    //some function that performs a check on student obj and updates the tookTest status to true
    function updateTookTest (uint ID) public {
        student.updateStudent(ID);
    }
    //if you want to access the public mapping
    function readStudentStruct (uint ID) public {
        test = student.studentNames(ID);
    }
}

I can see the call resolves correctly so it's not an issue accessing the mapping and the struct, just storing it. Any ideas?

1 Answer 1

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The issue is that structures are tuples, so you must read them as tuples. The following code will works.

contract ClassRoom{

Student studentContract;
stu public test;

constructor(address _addr) {
    studentContract = Student(_addr);
}

function updateTookTest (uint ID) public {
}

function readStudentStruct (uint ID) public view returns(string memory, 
uint, bool) {

    stu memory student;
    (student.name, student.age, student.tookTest) = 
    studentContract.studentNames(ID);
    return (student.name, student.age, student.tookTest);
}
}

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