how do I call a public interface method from the ui?

[dckc]

I saw this question today in discord...

Hi, how do I call a public interface method from the ui?

I can connect the vstorage, get the contract, use ChainStorageWatcher to get the instance but I don't find any tutorial on how to call a method defined in the public interface

stay tuned for an answer. cc @Jovonni @amessbee

[dckc]

As explained in Building Client Dapps

Clients interact with the consensus layer by making queries and submitting messages in signed transactions.

If the public facet method is a "get", the client often wants not just one answer, but a stream of answers as the current value changes.

In that case, you can somewhat simulate a call on the public facet by

• providing a notifier from the client's public interface
• subscribing to the notifier from within the contract and for each update, feed the contents thru vstorage
• querying / watching vstorage from a client

If the public facet method is not a "get", then you should be able to accomplish it with invitations and offers as discussed in the docs above.

I can imagine this is overly brief. Please ask questions where it's not clear. Or perhaps one of my colleagues will find a moment to give examples.

[yribero]

My current intent is to create and deploy a contract for storing notes (simple strings) into an array on the contract and retrieve them with a getter, watching if new ones are added.
I defined two functions in my publicFacet: getNotes and addNote. I would like to call those methods, and I hope only addNote requires to create a transaction.
I can't find any examples how to achieve this result. Though I understand this explanation in principle, it is still way too abstract to turn it into working code. I appreciate any help. In the discord #dev channel I go by the name fenner.

[dckc]

The agoric platform doesn't have a special case for query methods in contracts. (Whether it could or should is a longer discussion...)

Instead, it has vstorage / chainStorage.

The addNote method can publish to chainStorage, and the ui code can query vstorage.

I see @amessbee put together a quick example where the contract does...

      await storePatientData(patientData.patientId, patientData);

-- https://github.com/amessbee/dapp-med-rep/blob/b0f3adb041d9383a7badee12b51bf457cce0e473/contract/src/med-rec-contract.js#L84C1-L84C66

The publishHandler function is close to an addNote function. Since this contract isn't actually trading assets, the indirection around makePublishInvitation is unfortunate overhead. We have sketches for avoiding that eventually, but for now, that's the way it works.

On the ui side, getNotes is implemented as a fetch:

  const fetchPatientData = async (patientId: string) => {
    setSelectedPatientId(patientId); // Set the selected patient ID
    const response = await fetch(`${ENDPOINTS.API}/agoric/vstorage/data/published.patientData.patients.${patientId}`);

https://github.com/amessbee/dapp-med-rep/blob/b0f3adb041d9383a7badee12b51bf457cce0e473/ui/src/App.tsx#L333C1-L335C119

[yribero]

Hi, thank you very much for the pointer.

[dckc]

EVM analog: views

• Solidity - View and Pure Functions - GeeksforGeeks

[dckc]

How can I react (as a neutral observer) to the publishing of notes?

The chainStorageWatcher API is designed for this. It's basically HTTP polling.

In order to react to new notes, you might want a published.notes.latest that increments each time a new note becomes available.

[yribero]

I managed to access the vstorage from my web app and read all the nodes I was interested in. Now I would like to do the same within the smart contract, but this seems trickier.
I have found a way to access the agoricNames

const ns = (await makeAgoricNamesAccess()).agoricNames

But that's not what I want: I need to access the notes (which are not under agoric names) but I am currently not able to. Any hints?

[yribero]

Some more context from discord:

How do I access nodes create d in a smart contract? For example I can create a collection in my contract like this:

const notes = await E(privateArgs.storageNode).makeChildNode('collection');

And then push a note into it:

    const noteNode = await E(notes).makeChildNode(note.id.toString());
    const marshalledData = JSON.stringify(await E(marshaller).toCapData(note));
    await E(noteNode).setValue(marshalledData);

But later I'm not able to read them. These nodes don't have a getValue method, or any value/children reading method, for that matters.

I can access agoricNames and lookup stuff

const ns = (await makeAgoricNamesAccess()).agoricNames

But not my data whose root is at the same level as the agoricNames

[dckc]

How do I access nodes create d in a smart contract?

chainStorage, the contract-side API, is write-only.
vstorage, the client-side API, is read-only.

As I mentioned Oct 30, the norm is:

• a contract provides a public facet method such as getPublicTopics(). Peers inside the VM can use that to subscribe to updates.
  • in this case, a latestNoteId topic would let peers inside the VM subscribe to new notes
  • an E(publicFacet).getNote(id) method would let peers inside the VM get the contents of any note
• the contract subscribes to its own topics and reflects them into vstorage for off-chain clients

@amessbee perhaps you could update your demo app to show this pattern?

@yribero I can elaborate during office hours. The next one is tomorrow.

[yribero]

Thank you once more. I will try to attend the event