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Scripts and Flow ​

OpalScript and Flow share one component registry. Attach the script, then the graph can call it.

Methods that become nodes ​

OpalScriptIn Flow
public void Collect()Component action
public bool IsSpinning()Component condition
public async Task<int> Charge()Action with Started, Completed, Canceled, Failed paths
Lifecycle (Start, Update, FixedUpdate, End)Engine only — not nodes

Typed parameters become Flow inputs. [Pure] opts a synchronous helper into checked read-only behavior, including transitive calls. An ordinary public bool condition can still run commands.

Public async methods can return Task<T> with typed completion results. Flow uses the same outcomes as the Tasks panel. See task outcomes in Flow and Tasks.

Call a script from Flow ​

A public void method on an attached class becomes a component action. Engine hooks such as OnTap are not Flow nodes — the high-level coin uses OnTap in the class itself.

csharp
class Coin : Component {
    public void Collect() {
        Game.SetNumber("score", Game.GetNumber("score") + 1);
        Scene.Destroy(Self);
    }
}

After you attach Coin and declare score:

text
On Tap
  → Coin.Collect

Collect adds one to GameState and destroys the object.

Script node ​

Flow also has a Script node for a one-off snippet (current object, event params, components). Keep those named. A graph full of anonymous blocks is harder than either pure Flow or a reusable project class.

Use a Script node between an event and an action when you are prototyping, then promote it to a class method when you reuse it.

Events ​

An OpalScript public event Payload Opened appears under that component in Flow, with an aggregate Payload pin and typed member pins. Optional values expose presence separately. [EventId("opened")] keeps the Flow key stable across renames. See typed events.

HUD and UI ​

Score labels are the easy case: Data bindings → GameState in the UI Inspector. See UI and HUD.

When a label needs a derived number (a percent, a price), expose a [Computed] getter — typed HUD bindings. Buttons that call a method: direct UI actions.

What not to mix up ​

  • UI score labels use Data bindings → GameState. Flow writes GameState with Set Value / Add Counter, or =GameState.score in a Flow expression. Scripts use Game.SetNumber("score", …).
  • opal.component declarations are not typed GetComponent<T>() targets. Look up OpalScript classes and native types.
  • Flow as text is the same graph as nodes — it is not OpalScript.