State field

State Fields are simple wrappers around storing values.

Also read key.field or Fields guide.

.get()

Returns the current value of the derived field in a StoreState.

Signature:

field.get(storeState: StoreState): FieldValue

Arguments:

• StoreState - The store state to get value from

Returns:

• The current value of field stored in the store state.

Example:

// Initialize a Field with a default value of 0
const counterField = key.field(0);
 
counterField.get(store.state) // 0

.initialValue

The initial value of the field.

Signature:

field.initialValue: Value

Example:

// Initialize a Field with a default value of 0
const counterField = key.field(0);
 
counterField.initialValue // 0

.update()

Helps build a transaction for updating the state field.

Signature:

field.update<TVal>(val: TVal | ((val: TVal) => TVal)): Transaction

Arguments:

• val - The value to update the field with. Can be a value or a function that takes the current value and returns a new value.

Returns:

• Transaction - A transaction that can be dispatched to the store.

Example:

const counterField = key.field(0);
 
store.dispatch(
  counterField.update(1) // Update the counter to 1
)
 
// callback version
store.dispatch(
  counterField.update((val) => val + 1) // Add one to whatever the current value is
)