Solidity: Return array of structs now support?

[EasonWang01]

Is it support now for solidity?

struct User {
    uint id;
    string name;
    string age;
    uint salary;
}
User[] public users;

function queryuser () returns ( User[] ) {
    return users;
}

Thanks for reply.

[chriseth]

Try pragma experimental ABIDecoderV2; on a 0.4.17 compiler.

[EasonWang01]

The remix IDE says below:

 SyntaxError: Unsupported experimental feature name.
pragma experimental ABIDecoderV2;

pragma experimental ABIDecoderV2;


contract test {
.....
}

Version:

Your current Solidity version is
0.4.17-nightly.2017.9.19+commit.1fc71bd7.Emscripten.clang

[chriseth]

oh I'm sorry - it's ABIEncoderV2.

[EasonWang01]

When execute the return array function it says below

Value: "0x0000000000000000000000000000000000000000000000000000000000000020000000000000000000000000000000000000000000000000000000000000000100000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000008000000000000000000000000000000000000000000000000000000000000000c000000000000000000000000000000000000000000000000000000000000000c80000000000000000000000000000000000000000000000000000000000000003656173000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000043078303000000000000000000000000000000000000000000000000000000000"
Decoded: Failed to decode output: Error: Unsupported or invalid type: tuple

function

    function queryuser() public constant returns(User[]) {
        return users;
    }

    function addUser(uint _salaryId, string _name, string _userAddress, uint _salary) public  
      returns(uint) {
        users.length++;
        users[users.length-1].salaryId = _salaryId;
        users[users.length-1].name = _name;
        users[users.length-1].userAddress = _userAddress;
        users[users.length-1].salary = _salary;
        return users.length;
    }

[axic]

@EasonWang01 this seems to be a limitation in the decoding library you are using (possibly web3.js).

[EasonWang01]

Was using Remix IDE,is it possible to decode it?

[axic]

Not in Remix currently.

[EasonWang01]

Do you know how to decode it if not using Remix?
Thanks

[VoR0220]

@EasonWang01 that will need to be written up. I'm not sure if any of the ABIs support it just yet.

[mimitc123]

@EasonWang01 Has the problem been solved

[srameshr]

Still cant return array of struct?

[chriseth]

Any help is appreciated!

[wjmelements]

Returning structs in general seems to work only for automatic public accessors and fail otherwise.

pragma solidity^0.4.19;
pragma experimental ABIEncoderV2;

library L {
    struct Data {
        uint c;
    }
    struct Storage {
        Data[] data;
    }

    function inc(Storage storage self)
    internal {
        self.data.push(Data(self.data.length));
    }
}
contract C {
    using L for L.Storage;
    L.Storage lib;
    L.Data[] data;
    L.Data[] public publicArray;
    L.Data public publicSingle;

    function push()
    external {
        lib.inc();
        data.push(L.Data(data.length));
        publicArray.push(L.Data(data.length));
    }
    function getLib(uint i)
    public view returns (L.Data) {
        return lib.data[i];
    }
    function get(uint i)
    public view returns (L.Data) {
        return data[i];
    }
}

In remix IDE the failure is "Failed to decode output: Error: Unsupported or invalid type: tuple". I get a similar error in web3.js.

[wjmelements]

The difference in the ABI between the cases that decode and the cases that don't is the output type.

"outputs":[{"name":"c","type":"uint256"}] works

"outputs":[{"components":[{"name":"c","type":"uint256"}],"name":"","type":"tuple"}] fails to decode

Why is there indirection about "components"? The array of dictionaries was already sufficient to describe a struct type, and was already implemented by several decoders.

[wjmelements]

Workaround here: https://github.com/ethereum/browser-solidity/issues/920#issuecomment-348069589

[chriseth]

@wjmelements web3.js is still lacking an implementation for structs. ethers.js should already be fully compliant. The components-indirection was needed, because the type value is of type string. We considered making it either string or array, but people more used to JS/JSON advised against it.

[ThomasMW]

Is there any progress yet, in either Remix or Web3.js? I can't see the current workaround.

[wjmelements]

@ThomasMW they renamed the repo, which killed that link. Here is the new link: https://github.com/ethereum/remix-ide/issues/920#issuecomment-348069589

[comeonbuddy]

according to the answer in the url https://github.com/ethereum/remix-ide/issues/920#issuecomment-348069589 which is

function all(uint pos) public constant returns(uint id, uint value, uint time){ 
DonateInfo storage di = list[pos];
return (di.id, di.value, di.time)
} 

But it is not returning the whole list of array tho, it is taking in an uint and output a specific struct, similar to array[unit]?

[clrke]

Yup, is it not possible to get all DonateInfos?

[kyriediculous]

Breaking down the struct into an array will not work either without converting strings to bytes and back, it's quite the messy workaround as well imo.

Using 0.4.22 and experimental ABIEncoderV2 still getting the error.

It would be really cool if this could receive some priority, I imagine many devs would like to see this feature. Not trying to be pushy here :smile: .

Wouldn't having a struct as a real object be an "easy" solution? Not that I have any clue what I'm talking about here.

Another workaround is constructing your array on the client side with .map() (from an array of integers) I guess...

[Ajit666]

"error": "Failed to decode output: Error: Unsupported or invalid type: tuple"

[kyriediculous]

Why is this closed ?

[axic]

Because it has been supported since 0.4.17 by the compiler.

[kyriediculous]

is it?. Using nightly builds or experimental encoders doesn't really qualifiy as supported imo.

[adrianmcli]

I agree that this should be re-opened. Trying to return an array of structs is still an active issue in the community.

[chriseth]

You have to activate an experimental feature: https://github.com/ethereum/solidity/issues/2948#issuecomment-331182206

Having this issue open does not speed up the completion of the experimental feature.

[d-saravanan]

how do i return a mapping or a array from a solidity function

[wjmelements]

You cannot return a mapping.

[erak]

@ANUDAVIS Could you please share an example? Without any code, it's hard to reason about your issue. In general, this should work:

pragma solidity >0.5.6;
pragma experimental ABIEncoderV2;

contract Contract {

    struct Entry {
        uint id;
    }

    function getEntries() public returns (Entry[] memory) {
        Entry[] memory entries = new Entry[](1);
        entries[0] = Entry(1);
        return entries;
    }
}