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Sub-states & linked machines

Nest state machines and reuse flows from other assets.

As a flow grows, group related states into a sub-state machine: a graph of its own that shows up in the parent as a single node. Use a linked machine to reuse a whole flow that lives in another StateFlow Asset.

StateFlow Editor — Adventure
The Adventure graph: a Menu state, a Level sub-state node listing Playing (entry), Pause, Win and Lose (exits), and a linked Shop node listing Store and Purchase.
Level is a sub-state machine and Shop is linked from Shop.asset. Each lists its entry state and its exit states with their ports.

Sub-state machines

  1. Right-click the graph and choose Create › New › Sub-State, then name it.
  2. Double-click the node to open its graph. The breadcrumb at the top shows where you are; click a parent to go back. The State machine dropdown in the toolbar jumps straight to any machine in the asset.
  3. Add states inside as usual and mark one as its entry state. A transition into the sub-state node arrives there.
  4. Mark the states that can leave the sub-state as exit states. Their triggers appear as ports on the sub-state node in the parent graph, and you wire them to the parent's states there.
StateFlow Editor — Adventure › Main › Level
Inside Level: Playing leads to Pause, Win and Lose popups, each marked with an exit icon. Resume and Retry ports show a hidden-eye icon.
Inside Level. Resume and Retry connect back to Playing in here, so they are hidden on the parent.

Hiding exit ports

An exit state's internal triggers, like Resume on a pause popup, don't need to clutter the parent graph. Click the eye next to a port on an exit state to hide it from the parent. Hidden ports still work inside the sub-state.

Existing sub-states

Create › Existing › Sub-States places another node for a machine that already exists in the asset. Use Duplicate on a sub-state node to copy the machine with all its states and transitions.

Linked machines

A linked machine points at another StateFlow Asset and shows its main machine as a node, like a sub-state. Edit the flow in its own asset, and every graph that links it picks up the change. Build a Shop, a Settings flow or a login flow once and link it from each game or scene that needs it.

  1. Build the shared flow in its own StateFlow Asset, with an entry state and exit states.
  2. In the parent graph, choose Create › Linked State Machine and pick the asset.
  3. Wire the linked node's exit ports to the parent's states. Each linking graph wires them its own way.
StateFlow Editor — Shop
Shop.asset on its own: Store (entry and exit) leads to Purchase (exit). Store's Buy port is hidden from parents.
Shop.asset on its own. The Adventure graph only sees Store's Back port and Purchase's Ok port.
Note

A linked asset is loaded with the load type of the asset that links it, not its own. Keep linked assets on the same load type as their parents; the StateFlow Asset inspector flags any mismatch.

At runtime

Sub-states and linked machines are an editor-side organisation tool. At runtime, every state from every machine and linked asset is part of one flow, and the layer rules apply across them as usual. In play mode, open any machine to see its active state and last transition; turn on Follow to keep the active state in view.

Play mode — Level
In play mode inside Level, the Pause popup is highlighted as active and the Pause transition from Playing is lit.
The Pause transition just fired inside Level.
Play mode
The Paused popup with Resume and Quit to Menu buttons.
Quit to Menu leaves the sub-state through its exit port.
Try it

Import Feature Samples from the Package Manager and open 07 Sub-States and Linked Machines/07 Sub-States and Linked Machines.unity. About the samples