How can I update data on IPFS

Question

I am storing user information on IPFS in JSON object format and then storing that file hash on blockchain. I want to update that JSON object array every time I add a new user object. How can I achieve this?

I'm using Etherium Blockchain and ReactJS

Can you share the code that you've tried? – Miguel Mota Dec 26 '20 at 22:39 — Miguel Mota, Dec 26 '20 at 22:39

score 3 · Accepted Answer · answered Dec 26 '20 at 22:39

3

IPFS hashes are based on the content so the IPFS hash will change when the JSON data changes in this case. This means the content hash on-chain will have to be updated.

Read current JSON data from IPFS
Update JSON data with new entry
Add new JSON data to IPFS
Update content hash on smart contract

answered Dec 26 '20 at 22:39

Miguel Mota

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is there any code example or how we can do this? – Muhammad Zaryab Rafique Nov 08 '22 at 10:13

score -2 · Answer 2 · answered Dec 26 '20 at 21:42

Below is an example of a smart contract that can be used to maintain a list of links to user objects.

Each user is assigned a unique identifier (for example, a GUID without delimiters just fits in bytes32). Method PutUser is used to add / update a link to the user's object. The GetUser method is used to get a link to the user's object. Method GetUsersList is used to get a list of users.

When you change the some user's object, you put it again in the IPFS and add a new link using the PutUser

pragma solidity >=0.5.8 <0.6.0;

contract UsersList
{
    address    Owner ;

    struct IpfsLink
    {
      bytes32  used ;
       string  link ;
    }

    mapping (bytes32 => IpfsLink)  UsersIpfsLinks ;

    bytes32[]  Users ;

//
   constructor() public
   {
              Owner     = tx.origin ;
   }
// 
   function PutUser(bytes32  user_, string memory ipfs_link_) public
   {
       if(msg.sender!=Owner)  return ;

       if(UsersIpfsLinks[user_].used!="Y")
       {
             UsersIpfsLinks[user_]=IpfsLink({ used: "Y", link: ipfs_link_ }) ;

                    Users.push(user_) ;
       }
       else
       {
             UsersIpfsLinks[user_].link=ipfs_link_ ;
       }
   }
//
    function GetUser(bytes32  user_) public view returns (string memory retVal)
    {
       return(UsersIpfsLinks[user_].link) ;
    }
//
    function GetUsersList() public view returns (bytes32[] memory retVal)
    {
       return(Users) ;
    }

}

How can I update data on IPFS

2 Answers2