"Member not found or not visible" when trying to access individual struct members

Question

I'm new to Solidity and coding in general and this code may be a disaster, but I'm learning.

Basically, I'd like to get members of a struct with a function. I can return the entire struct in the form of a tuple in another function (getPairData()), but not when trying to return individual members. When I try accessing the members (getPairMembers()) - I get an error: struct member not found or not visible after argument dependent lookup in struct MapTest.Pair storage... (see photo below)

I think this code may be a little hacky - I wasn't sure how to keep track of multiple datasets from the same user. I tried making a mapping to an array of the structs, but couldn't figure out how to access each one individually so I mapped every address to an integer mapped to the struct array to act as a sort of index(?)

Here's my code:

pragma solidity ^0.8.0;

contract MapTest {

struct Pair {
    uint256 token1;
    uint256 token2;
    uint256 breedStart;
    uint256 breedEnd;
}

mapping(address => mapping(uint256 => Pair[])) userPairs; 
mapping(address => uint256) pairCount;
mapping(uint256 => bool) isBreeding;

function getRandom() public view returns(uint256){
    uint256 time = block.timestamp;
    uint256 rand = uint256(keccak256(abi.encodePacked(time)));
    
    return (rand % 360);
}

function breed(uint256 _token1, uint256 _token2) public {
    require (isBreeding[_token1] == false && isBreeding[_token2] == false);

    uint256 breedTime = getRandom();
    uint256 time = block.timestamp;
    
    Pair memory pairTest;
    
    pairTest.breedStart = time;
    pairTest.breedEnd = time + breedTime;
    pairTest.token1 = _token1;
    pairTest.token2 = _token2;
    
    userPairs[msg.sender][pairCount[msg.sender]].push(pairTest);
    isBreeding[_token1] = true;
    isBreeding[_token2] = true;
    
    pairCount[msg.sender]++;
    //function for burning incubator here
}


function getPairData(address _wallet, uint256 _index) public view returns(Pair[] memory){
    return userPairs[_wallet][_index];
}

function getPairMembers(address _wallet, uint _index) public view returns(uint256, uint256, uint256, uint256){
    return (userPairs[_wallet][_index].token1, 
            userPairs[_wallet][_index].token2, 
            userPairs[_wallet][_index].breedStart, 
            userPairs[_wallet][_index].breedEnd);
}

}

The error code I receive is this:

Any help would be greatly appreciated.

Answer 1

The logic you used is actually for: mapping(address=>mapping(uint=>Pair)) which is the structure itself instead of the struct array you're defining inside the mapping. To access token1 value, you'll first need to push the items into the Pair[] array like you did here: userPairs[msg.sender][pairCount[msg.sender]].push(pairTest) and then iterate through the mapping array with a for loop.

for(uint i=0;i<userPairs[msg.sender][pairCount[msg.sender]].length;i++)
{
 return userPairs[msg.sender][pairCount[msg.sender]][i].token1;
}