Trigger

Trigger is a deterministic reactive state framework for Flutter.
It enforces a static acyclic dependency graph at initialization, It enforces a static acyclic dependency graph at initialization — guaranteeing predictable updates, eliminating structural cycles, and simplifying data flow reasoning.

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Why Trigger?

• Deterministic by Design
  Trigger locks the dependency graph at init-time. No hidden structural cycles. No runtime graph mutations. Your app’s state updates are predictable by construction.

• Cycle Detection Built-in
  Effects are validated with BFS cycle detection during initialization. If a circular dependency exists, Trigger throws immediately — saving you from runtime headaches and impossible-to-test scenarios.

• Debugging Made Clear
  With dumpDepsGraph(), you can visualize the dependency graph in seconds. See which fields impact which effects, and reason about your data flow without guesswork.

• Separation of Concerns
  Effects live outside the UI. Business logic and state transformations are explicit, structured, and easy to reason about.

• Simple Mode or Structural Mode

  • Simple: Use Trigger without Effects — lightweight, no ceremony.
  • Structural: Add Effects for deterministic data flow — more ceremony, but less cognitive load and easier testing.

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Philosophy

Trigger trades a little ceremony for clarity and robustness.
It reduces structural and defensive testing overhead, eliminates defensive coding against cycles, and lowers cognitive load when reasoning about complex state flows.

Trigger guarantees deterministic update order within the dependency graph by enforcing a static acyclic dependency graph at initialization.

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Example

@TriggerGen("MainStates", fx: [BMIEffect])
class Decl {
  int counter = 0;
  double weight = 0;
  double hight = 0;
  double bmi = 0;
}

final class BMIEffect extends MainStatesEffect {
  BMIEffect(super.trigger);

  @override
  final listenTo = MainStates.fields.weight.hight;

  @override
  final allowedMutate = MainStates.fields.bmi;

  @override
  void onTrigger() {
    final h = hight / 100;
    bmi = weight / (h * h);
  }
}