Solidity Function Limits – Is There a Limitation on Number of Return Values?

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Answer of this question (https://ethereum.stackexchange.com/a/3590/4575) says that: "I am not allowed to return dynamic arrays from Solidity functions yet."

On the other hand, Solidity supports functions with multiple return values. How can I return multiple strings from a contract function?

[Q] Is there any limitation for the number of the return values in one function call. Such as, could I return N (for example N=1000) number of values or even more in one function call?

function getData() constant returns (bytes32, bytes32, bytes32, bytes32, 
                                     bytes32, bytes32, bytes32, ...) {
    bytes32 a = "a";
    bytes32 b = "b";
    bytes32 c = "c";
    bytes32 d = "d";
    bytes32 e = "e";
    bytes32 f = "f";
    bytes32 g = "g";
    return (a, b, c, d, e, f, g, ...);
}

Thank you for your valuable time and help.

Best Answer

In practice, the call stack imposes a limitation in current implementations.

The following contract will face a 'Stack too deep' compiler error.

pragma solidity ^0.4.3;

contract Test {
    function getData() constant returns (bytes32, bytes32, bytes32, bytes32,
                                     bytes32, bytes32, bytes32, bytes32,
                                     bytes32, bytes32, bytes32, bytes32,
                                     bytes32, bytes32, bytes32) {                                         

        return ("a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k", "l", "m", "n", "o");                                         
    }
}

Browser Solidity:

https://ethereum.github.io/browser-solidity/#gist=ac9812a045a41fd4168f2e352732962d

Gist URL:

https://gist.github.com/anonymous/ac9812a045a41fd4168f2e352732962d

Related Solutions

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.

Solidity – Handling Unimplemented Functions in Contracts

The problem is that totalSupply() implementation is missing. Seems like autogenerated getters do not count. So you need to explicitly create the function.

contract StandardToken is Token {
    uint256 _totalSupply;

    function totalSupply() constant returns (uint256 totalSupply) {
        totalSupply = _totalSupply;
    }
}

Best Answer

Related Solutions

Solidity Return Struct – Creating and Using Data Structures

Solidity – Handling Unimplemented Functions in Contracts

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