[Unity] How to implement a `Action` logics(feat. TransferAsset)

:bulb: This article was written based on Nine Chronicles version v100301[1].

Structure of handling actions in Unity

    participant View
    participant ActionManager
    participant Agent
    participant ActionRenderHandler
    Note over ActionRenderHandler: Observe the render event of the action
    Note over View: Click the button
    View ->>+ ActionManager: Request to create an action
    Note over ActionManager: Create an action
    ActionManager ->> Agent: Request to create a transacsion
    Note over Agent: Create a transaction
    ActionManager ->>- View: Returns an observable of a render event
    activate View
    Note over View: Observe
    Note over Agent: Do blockchain node stuffs
    Note over Agent: A new block was mined
    Agent --)+ ActionRenderHandler: Broadcast
    Agent --) View: Broadcast
    deactivate View
    Note over ActionRenderHandler: Update game state
    ActionRenderHandler ->>- View: Update view
    Note over View: Update

Check actions on lib9c

The first thing to do is to check lib9c for the actions we want to deal with in 9c-unity.

This document covers an action called ‘TransferAsset’.

TransferAsset actions list

There are several TransferAsset actions in lib9c as shown below.

class name action type
TransferAsset “transfer_asset3”
TransferAsset0 “transfer_asset”
TransferAsset2 “transfer_asset2”

In lib9c, actions that are responsible for specific functions are often upgraded to fix bugs or improve functions. And this is done by leaving the original as is and adding a new version of the action, where the class name and action type follow the convention for setting them as shown below.

Change of the action class name and action type by action upgrade

Step 1. Create a new action class with new action type

  • Create a new class as pascal case.
  • Set the action type as snake case of the class name.
class name action type desc
TransferAsset “transfer_asset” new one

Step 2. Upgrade the action

  • Rename class name of old one consider action type.
  • Create a new class as pascal case.(without version number)
  • Set the action type of the new class above as snake case with a version number.
  • The version number starts with 2.
class name action type desc
TransferAsset “transfer_asset2” new one
TransferAsset0(or TransferAsset1) “transfer_asset” old one

Step 3. Upgrade the action

class name action type desc
TransferAsset “transfer_asset3” new one
TransferAsset0(or TransferAsset1) “transfer_asset” old one
TransferAsset2 “transfer_asset2” old one

Obsoleted action

When upgrading an action, we usually obsolete the action from the previous version so that it is no longer available.

The obsolete processing status of the TransferAsset action.

class name action type is obsoleted
TransferAsset “transfer_asset3” no
TransferAsset0(or TransferAsset1) “transfer_asset” yes
TransferAsset2 “transfer_asset2” no

As you can see above, There are cases where we didn’t set the old actions to obsolete.

In 9c-unity, we are handling actions which is not obsoleted and I use the TransferAsset class in this article.

Action creation

Responsibility for creating actions rests with ActionManager.
I wrote a method that creates a TransferAsset action below.

public IObservable<ActionBase.ActionEvaluation<TransferAsset>> TransferAsset(
    Address sender,
    Address recipient,
    FungibleAssetValue amount,
    string memo)
    // Create an action.
    var action = new TransferAsset(

    // Request to create a transaction to IAgent inside of ProcessAction method.

    // Return observable of the first render of the `TransferAsset` rendered from now.
    return _agent.ActionRenderer.EveryRender<TransferAsset>()

I found above method does not work and I improved it from this pull request.

Action render event handling

In 9c-unity, most action render events are handled by ActionRenderHandler.
And the render event handling method of the TransferAsset action has already been written here.

private void ResponseTransferAsset(ActionBase.ActionEvaluation<TransferAsset> eval)
    // Check the action has an exceptions.
    if (!(eval.Exception is null))

    var senderAddress = eval.Action.Sender;
    var recipientAddress = eval.Action.Recipient;
    var currentAgentAddress = States.Instance.AgentState.address;
    var playToEarnRewardAddress = new Address("d595f7e85e1757d6558e9e448fa9af77ab28be4c");

    // If sender address of the TransferAsset action equals to current agent address,
    if (senderAddress == currentAgentAddress)
        var amount = eval.Action.Amount;

        // Call some UI system.
            L10nManager.Localize("UI_TRANSFERASSET_NOTIFICATION_SENDER", amount, recipientAddress),
    // else if recipient address of the TransferAsset action equals to current agent address,
    else if (recipientAddress == currentAgentAddress)
        var amount = eval.Action.Amount;
        // // If sender address of the TransferAsset action equals to specific address,
        if (senderAddress == playToEarnRewardAddress)
            // Call some UI system.
                L10nManager.Localize("UI_PLAYTOEARN_NOTIFICATION_FORMAT", amount),
            // Call some UI system.
                L10nManager.Localize("UI_TRANSFERASSET_NOTIFICATION_RECIPIENT", amount, senderAddress),

    // Update agent state on game state asynchronously.

Handling Action Render Events in the UI

Now, based on what I introduced above, it is possible to create an action from the UI and update the UI based on a specific event.

public class TransferAssetView : MonoBehaviour
    private Address _senderAddr;
    private Address _recipientAddr;
    private FungibleAssetValue _amount;
    private string _meno;
    private Button _button;

    // Invoked from `ActionRenderHandler` or other context.
    public void OnActionRendered()
        // Do something.

    // Invoked when `_button` clicked.
    private void OnButtonClick()
            .TransferAsset(_senderAddr, _recipientAddr, _amount, _meno)

  1. lib9c:v100301, NineChronicles:v100301 ↩︎

1 Like

so if i created “transfer_asset4” it will accepted on miner part? or it should be “transfer_asset3” same as latest build?

All you need to do after creating “transfer_asset4” is to put a pull request to the upstream lib9c repository.
This is because other nodes do not know about the “transfer_asset4” you created. It also means that “transfer_asset4” is not agreed upon as a protocol.

1 Like