Returning bytes from array of structs

Question

In solidity do i return an array or structs in bytes.

This is not a duplicate of this question because that solution always returns the error: new BigNumber() not a number: [object Object]

pragma solidity ^0.4.2;
contract Something {
    mapping (address => Ton[]) allTons;

    struct Ton { 
        uint id;
        string name;
        bool access;
    }

    function Something() public {
        allTons[msg.sender].push(Ton({
            id: 1,
            name: "CoolDude",
            access: true
        }));
        allTons[msg.sender].push(Ton({
            id: 2,
            name: "NotCoolDude",
            access: false
        }));
    }

    function GiveBytes() public constant returns(bytes){
        // unsure

    }


}

Possible duplicate of How contract method returns struct or array? — niksmac, Dec 21 '17 at 04:16

score 1 · Answer 1 · answered Dec 21 '17 at 06:23

I fiddled around with it until this works.

There is possibly a more elegant solution but you should be warned that returning arrays and structs is very new. Also, it will not scale as well as this pattern.

This will have a fixed gas cost at any scale by relying on the client to iterate over the function if wants the whole table.

pragma solidity ^0.4.18;

contract Something {

    mapping (address => Ton[]) allTons;

    struct Ton { 
        uint id;
        string name;
        bool access;
    }

    function Something() public {

        allTons[msg.sender].push(Ton({
            id: 1,
            name: "CoolDude",
            access: true
        }));

        allTons[msg.sender].push(Ton({
            id: 2,
            name: "NotCoolDude",
            access: false
        }));
    }

    // fish them out one row at a time
    // and return a simpler response.

    function getTonAtRow(address user, uint row) public constant returns(uint, string, bool) {
        return(allTons[user][row].id, allTons[user][row].name, allTons[user][row].access);

    }

}

More elaboration over here: Are there well-solved and simple storage patterns for Solidity?

Hope it helps.

Well this doesnt really help for the array of structs, – Alain Goldman Dec 21 '17 at 15:40 — Alain Goldman, Dec 21 '17 at 15:40

score 0 · Answer 2 · answered May 15 '18 at 11:35

Just declare your mapping AllTons as public and you will get a default getter function that takes an address and the index of the array. Then define a function to return the number of items in the array, given an address. Iterate the getter function to get all your items.

pragma solidity ^0.4.23;

contract Something {

    mapping (address => Ton[]) public allTons;

    struct Ton { 
        uint id;
        string name;
        bool access;
    }

    constructor() public {

        allTons[msg.sender].push(Ton({
            id: 1,
            name: "CoolDude",
            access: true
        }));

        allTons[msg.sender].push(Ton({
            id: 2,
            name: "NotCoolDude",
            access: false
        }));
    }

    // Get the items count first,
    // then use the default allTons getter to get each item.

    function getTonCount(address _address) public view returns (uint _count) {
        _count = allTons[_address].length;        
    }

}

Returning bytes from array of structs

2 Answers2