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Action

Atom is the core of the atomic state. It allows creating an object that stores an autonomous micro-state, observable by anything—whether a widget or a function. However, an Atom could be modified by anything, anywhere, leading to classic side-effect problems. To address this, we removed the state setter and added AtomAction. This ensures that while an Atom can be listened to by anything, it can only be modified in a specific place, enhancing predictability and reducing uncontrolled side effects.

// Atom creation
final counterState = atom(0);

// Listen to changes
counterState.addListener(() {
    print(counterState.state); // 1
});

// Action creation
final increment = atomAction((set) {
    set(counterState, 1);
});

// Execute action
increment();

This simple limitation provides significant predictability in state propagation. The scope of AtomAction contains the set property, which is the only way to update a state. You can have AtomAction with up to 3 parameters:

  • atomAction1
  • atomAction2
  • atomAction3

Example:

final counterAction = atomAction1<String>((set, action) {
    final state = counterState.state;

    if(action == 'INCREMENT') {
        set(counterState, state + 1);
    } else if(action == 'DECREMENT') {
        set(counterState, state - 1);
    }
});

counterAction('INCREMENT');

This versatility allows for a simple common call, a pub-sub mechanism, or even turning an action into a state reducer, making everything more interesting.