[Ethereum] Return a struct from a Solidity Contract

soliditystruct

I'm just trying to get confirmation as to whether this is supported within Solidity currently. Older responses to this question seem to imply this has been added, but I can't find any concrete literature to confirm.

If I have a struct within the contract, can I return it via a getter on the contract? For example:

struct myDetails {
    string firstName;
    string lastName;
}

function getName() returns (???) {
    return myName;
}

Thx

Marty

Best Answer

It's not currently possible to return a struct to the outside with your own function. Nonetheless, it's possible with Solidity's automatically generated getters.

By marking a variable public (for example uint public someNumber) Solidity will automatically generate a getter (someContract.someNumber()). This will indeed work on structs (Foo public someFoo) and even arrays and mappings! (mapping(uint => player) public players) In the last case, you provide a key to the getter to get the one you want. (someContract.players(7))

One caveat: Nested structs, arrays, and mappings inside of structs are currently not returned by getters. Strings, however, are.

Related Solutions

Go-Ethereum – Uncaught Error: new BigNumber() Not a Base 16 Number

Base 16 is hexadecimal. The variable iPos you're giving to getFirstname is base 10 IE "0"

Hexademical is 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E,F <-- Sixteen positions.

Demical is 0,1,2,3,4,5,6,7,8,9 <-- Ten positions.

The number zero in Base 16 is 0x0.

Solidity Return Struct – Creating and Using Data Structures

Update:

See here. We can return structs but only for internal calls.

Returning structs in new version in Solidity

In this snippet, function tryIt() returns true after a successful compile. It's just making an internal call (success). getAssetStructById() fails when called from outside.

pragma solidity 0.4.17;

contract Test {

    enum assetState{something}

    mapping(uint256 => asst) assetsById;

    struct asst {
        uint256 assetId;
        uint256 next;
        uint256 prev;
        uint256 timestampCreation;
        address assetOwner;
        address issuer;
        string content;
        uint256 sellPrice;
        assetState state;
    }

    function getAssetStructById(uint256 assetId) public view returns (asst _asset) {
        return (assetsById[assetId]);
    }

    function tryIt(uint id) public view returns(bool success) {
        asst memory a = getAssetStructById(id); 
        return true;
    }
}

Hope it helps.

Best Answer

Related Solutions

Go-Ethereum – Uncaught Error: new BigNumber() Not a Base 16 Number

Solidity Return Struct – Creating and Using Data Structures

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