Caching a contract query/promise

[ethernalquestion]

Searched everywhere but could not find a solution to this. I would like to cache a set of promises that would call contract.function.method, or contract.staticCall.method. My problem is that I am basically repeatedly doing these queries and I want to remove the overhead of building the promise every block. Is there a way to do this currently?

The closest I could get was to cache the queries for several different blockTags in the future, but unfortunately it seems like the actual query evaluates in the background even though the promise was not called with promise.all yet.

Really appreciate your help, thanks a lot!

[zemse]

There are certain queries like getBalance whose response can change so you may not want to cache them while some of the queries whose value never changes erc20token.symbol(), you would like to cache.

Now a quick approach can be to maintain a dictionary of all the cached values.

let cache = {};

setInterval(async() => {
  const balance = await contract.balanceOf('0xabc...');
  const symbol = cache['token-symbol'] !== undefined ? cache['token-symbol'] : (cache['token-symbol'] = await contract.symbol());
}, 5000)

The closest I could get was to cache the queries for several different blockTags in the future, but unfortunately it seems like the actual query evaluates in the background even though the promise was not called with promise.all yet.

I'm trying to understand this, can you explain this or maybe share a code snippet example?

[ricmoo]

I think what you are looking for is generating the transaction, to send later? You can use const tx = await contract.populateTransaction.methodCall(), which will return a Promise that resolves to the transaction. Later you can then use provider.sendTransaction(tx) to actually perform the call.

Is that what you meant? Once a Promise is constructed, its executor is evaluated immediately...

[ethernalquestion]

Thanks Ric and zemse. Ric thats precisely that I was looking for, I'm experimenting with this approach now, though unfortunately currently getting an "Error: invalid hexlify value " error when attempting to execute the provider.sendTransaction(tx) and trying to debug to find out the cause.. This is a view only call btw, so would be a query only

[ethernalquestion]

@ricmoo, any idea what could be causing this "Error: invalid hexlify value " ? Basically I call populateTransaction.methodCall(), it generates the payload correctly afaik but then when I call provider.sendTransaction(tx) it gives me the hexlify error.. (sorry for bothering you with probably whats a very basic question!)

[zemse]

Just trying to help, provider.sendTransaction (docs) expects the transaction to be signed i.e. a serialised transaction hex string. So the output of populateTransaction.methodCall() you need to sign it using signer to generate the serialized hex string and then pass this hex string into the provider.sendTransaction.

If you are using wallet, it's wallet.signTransaciton (docs), if you are using something like metamask, then signer.sendTransaction (docs) signs as well as submits the tx.

[ethernalquestion]

Thanks a lot Zemse and everyone. With Zemse's latest reply I was able to resolve this by going through the docs. Basically my transaction was a query rather than a write transaction so I had to do something slightly different than what you guys suggested:

• tx = await contract.populateTransaction.methodCall()
• later on when i need to use it, response = provider.call(tx )
• finally I had to decode the response, using interface.decodeFunctionResult, as the result from step 2 was encoded.
  Thanks again!