CODEWITHSUNDEEP
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Eddy
Eddy

Reputation: 3713

How to use an array of strings in a solidity mapping?

I need to store a mapping between a string to items which are 128 bytes long in a solidity contract. The problem is that the longest bytes data type is bytes32, which is not long enough, and if I try to store my strings in a string array I get the following error: 

This type is only supported in the experimental ABI encoder. Use "pragma experimental abiencoderv2;" to enable this feature

So I cannot use bytes32 because it's not big enough. I cannot use bytes because it's not supported. And I cannot use string[] because it's experimental and not recommended in production.

Any solution?

This is the contract I'm using: 

pragma solidity ^0.4.24;

contract SomeData {    
    struct Data {
        string id;
        string[3] items;
    }

    mapping (string => Data) dataItems;

    function addData(string id, string[3] items) public {
        Data memory data = Data(id, items);
        data.id = id;
        data.items = items;
        dataItems[id] = data;
    }

    function getDataItems(string id) public view returns (string[3]){
        return dataItems[id].items;
    }
}

Upvotes: 1

Views: 4409

Answers (1)

Adam Kipnis
Adam Kipnis

Reputation: 10991

Since you know the maximum length of each individual string, you can use a static 2 dimensional array:

contract SomeData {

    struct Data {
        string id;
        byte[128][100] items;
    }

    mapping (string => Data) dataItems;


    function addData(string id, byte[128][100] items) public {
        Data memory data = Data(id, items);
        data.id = id;
        data.items = items;
        dataItems[id] = data;
    }

    function getDataItems(string id) public view returns (byte[128][100]){
        return (dataItems[id].items);
    }
}

Note, only 2-dimensional dynamic arrays are not allowed. You could even use byte[128][] if you wanted to.

Upvotes: 1

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