Solidity invalid opcode error

Question

I am using a code to collect IDs from a structure and I am using the following code for it:

pragma solidity ^0.4.24;


contract MediaGallery {

address owner;

uint counter;


struct MediaAsset {

    uint id;

    string name;

    address author;

    uint createDate;

    string[] tags;

    string mediaHash;

}


mapping(address => MediaAsset[]) public mediaDatabase;


constructor () {

    owner = msg.sender;

}


function addMedia(string _name, string _mediaHash) public returns (bool success) {

    MediaAsset memory currentMedia;


    currentMedia.id = counter;

    currentMedia.name = _name;

    currentMedia.author = msg.sender;

    currentMedia.createDate = now;

    currentMedia.mediaHash = _mediaHash;


    mediaDatabase[msg.sender].push(currentMedia);


    return true;

}


function addTag(uint _id, string _tag) public returns (bool success) {

    mediaDatabase[msg.sender][_id].tags.push(_tag);


    return true;

}


function getMediaByAddress(address _user) public view returns (uint[]) {

    uint[] memory mediaAssetIds = new uint[](mediaDatabase[_user].length);


    uint numberOfMediaAssets = 0;


    for(uint i = 1; i <= mediaDatabase[_user].length;  i++) {

        mediaAssetIds[numberOfMediaAssets] = mediaDatabase[_user][i].id;

        numberOfMediaAssets++;

    }

    return mediaAssetIds;

}

}

But when I execute this code, I get invalid opcode error.

Answer 1

In the for loop, your indexing going beyond the array index. Your loop variable i has an off-by-one error. The highest value I can have is mediaDatabase[_user].length but in the loop, i is going for one value greater than this.

Modify you code to the following code:

for (uint i = 0; i < mediaDatabase[_user].length; i++) {

recompile and run, it should work.