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Stores are global containers of application specific data. They are defined with the store keyword:

store Counter.Store {
  state counter : Number = 0

  fun increment : Promise(Never, Void) {
    next { counter = counter + 1 }

  fun decrement : Promise(Never, Void) {
    next { counter = counter - 1 }

In the example above, we defined a store for a global counter with a function to increment it and one to decrement it.

Stores are:

  • global - which means they are accessible from anywhere (for example: Counter.Store.counter ). This also means all accesses update the same, shared data.
  • mutable - their data can be changed using a next call (but only inside the store)
  • they can only contain functions and states


States on a store define keys which correspond to specific type of values. They can be accessed by their name.

Connecting to components

Stores can be connected to components. To learn more, check out components.