I have a contract which acts as an auction house. Each Auction is a struct. Therefore, each time a user wants to sell an item, a new Auction struct is created in storage.

This wouldn't be a problem if I stored all the Auctions in one storage array. However, due to different query reasons, I need to have the same Auction reference, stored within multiple arrays.

I come from a Java/C# background, so in that sense, what makes sense to me is:

  1. Create an object on heap
  2. Get the reference to that object
  3. Add the reference to N arrays
  4. Changing the object from any of these arrays changes the data on the heap, thus effectively changing it for every array which holds a reference to it

The problem is, I have no idea how to pull this off in Solidity. Here is what my code does:

  1. mapping(uint256 => Auction) allAuctions keeps track of all auctions
  2. mapping(address => Auction[]) userAuctions keeps track of all auctions made by a wallet

What I tried to do is the following:

allAuctions[n] = Auction(); // I thought this would make an object "on the heap" and add a reference to the map

userAuctions[wallet].push(allAuctions[n]); // Push the reference from the map into the array

However, when I execute this, it doesn't work. It seems to me that 2 separate structs are being made in the storage, because changing 1 doesn't change the other.

Is there a way to make this work or is my paradigm completely incorrect? Thanks in advance.

1 Answer 1


Solidity doesn't have references. As everything in software engineering you can workaround that limitation using an indirection. Store all auction in a mapping or array and use auctionId to refer it from anywhere else.

 maping (uint256 => Auction) auctions;
 mapping(address => uint256[]) userAuctions;

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