ScalarSignal


The ScalarSignal class monitors a numerical value.

Properties

PropertyDescription

lastValue

(get) lastValue: number (set) (Not Available)

Specifies a number that represents the last value of the signal.

Note: The signal value is updated during simulation tick. This means that the value of lastValue is undefined before its first update. It is also undefined for signals that aren't used for any bindings/subscriptions, because those signals aren't guaranteed to be updated at each simulation tick.

Methods

MethodDescription

eq

eq(other: ScalarSignal): BoolSignal

Returns a Boolean signal that takes the value of true every time when the value of the left-hand-side signal is equal to the value of the right-hand-side one, and the value of false all other time.

Note: the scalar values are tested for exact equality. For some applications it might be reasonable to perform a non-strict comparison allowing the values to be within a small distance one from another.

See Also: ReactiveModule.eq

expSmooth

expSmooth(dampFactor: number): ScalarSignal

Smoothes a variable signal using exponential averaging over time. The argument specifies the dampening time constant in milliseconds.

Note: See also ReactiveModule.expSmooth.

format

format(formatString: string): StringSignal

Converts a ScalarSignal to a StringSignal according to the supplied formatting string.

Note: formatString shall conform to the Folly formatting rules as specified here: https://github.com/facebook/folly/blob/master/folly/docs/Format.md#format-string-syntax .

See Also: ScalarSignal.toString.

ge

ge(other: ScalarSignal): BoolSignal

Returns a Boolean signal that takes the value of true every time when the value of the left-hand-side signal is greater than or equal to the value of the right-hand-side one, and the value of false all other time.

See Also: ReactiveModule.ge

gt

gt(other: ScalarSignal): BoolSignal

Returns a Boolean signal that takes the value of true every time when the value of the left-hand-side signal is strictly greater than the value of the right-hand-side one, and the value of false all other time.

See Also: ReactiveModule.gt

interval

interval(threshold: number): EventSource

Returns an EventSource that emits an event whenever the supplied ScalarSignal first passes (becomes greater than or equal) a value of N*threshold, N = 1, 2, 3, ... Events are signaled in increasing order of N, starting from 1, with no omissions. For each value of N, the respective event is fired only once.

The emitted event (the argument passed to the callback function) has the value of corresponding N*threshold.

Note: The threshold must be a positive number.

Note: interval is mostly useful for non-negative non-decreasing scalar signals.

See Also: ReactiveModule.trigger, ReactiveModule.multiTrigger.

le

le(other: ScalarSignal): BoolSignal

Returns a Boolean signal that takes the value of true every time when the value of the left-hand-side signal is less than or equal to the value of the right-hand-side one, and the value of false all other time.

See Also: ReactiveModule.le

lt

lt(other: ScalarSignal): BoolSignal

Returns a Boolean signal that takes the value of true every time when the value of the left-hand-side signal is strictly less than the value of the right-hand-side one, and the value of false all other time.

See Also: ReactiveModule.lt

monitor

monitor(): EventSource monitor(config: { fireOnInitialValue: ?boolean}): EventSource

Returns an EventSource that emits an event every time the value of the input signal changes. The event contains a JSON object with the old and new values in the format:

{ "oldValue": val, "newValue": val }

Note: By default, there is no event fired for the initial value of the signal. If config.fireOnInitialValue is set to true then an event for initial signal value is also emitted. oldValue is unset for this initial event.

multiTrigger

multiTrigger(threshold: number): EventSource

Returns an EventSource that fires every time the signal raises to (becomes greater than or equal after being less than) the value of threshold.

The emitted event (the argument passed to the callback function) has the value of threshold.

Note: The initial value of the signal is assumed to be 0.0.

See Also: ReactiveModule.trigger, ReactiveModule.interval.

ne

ne(other: ScalarSignal): BoolSignal

Returns a Boolean signal that takes the value of true every time when the value of the left-hand-side signal is not equal to the value of the right-hand-side one, and the value of false all other time.

Note: the scalar values are tested for exact equality. For some applications it might be reasonable to perform a non-strict comparison allowing the values to be within a small distance one from another.

See Also: ReactiveModule.ne

pin

pin(): ScalarSignal

Returns a ScalarSignal containing a constant value which is the value of the specified signal immediately after pin is called.

pinLastValue

pinLastValue(): ConstScalarSignal

Returns a ConstScalarSignal containing a constant value which is the last value of the specified signal before pinLastValue is called. ConstScalarSignal can be passed to a functions which accept numbers.

schmittTrigger

schmittTrigger(config: { low: number, high: number, initialValue: ?boolean}): BoolSignal

Returns a Boolean signal that is true when the input is strictly greater than the upper threshold, and false when it is strictly less than the lower threshold. For input values between and including the thresholds, the Shmitt trigger returns the same value as at the previous update, or initialValue if this is the first update.

Note: The initialValue is assumed to be false if it isn't specified.

toString

toString(): StringSignal

Converts a ScalarSignal to a StringSignal according to the default string formatting rules.

Note: ScalarSignal.format allows more flexible control over the way the number is converted to string.

trigger

trigger(threshold: number): EventSource

Returns an EventSource that fires the first time the value of the signal raises (becomes greater than or equal) to the level of threshold. No more than one event is ever emitted by this EventSource.

The emitted event (the argument passed to the callback function) has the value of threshold.

Note: for positive thresholds, trigger is equivalent to interval(threshold).take(1).

See Also: ReactiveModule.multiTrigger, ReactiveModule.interval.

valueOf (inherited from ISignal)

valueOf(): void

Throws an error. Signals are not supposed to be implicitly converted to scalar values.

See also: ScalarSignal.add, ScalarSignal.sub, ScalarSignal.mul, ScalarSignal.div

Example

// Load in the required modules
  const Animation = require('Animation');
  const Scene = require('Scene');
  const TouchGestures = require('TouchGestures');

  // Access a plane inserted in the scene
  const plane = Scene.root.find('plane0');

  // Use pinLastValue as a way of getting the intial Y position of the plane
  const planeInitialYPosition = plane.transform.y.pinLastValue();
  // Define an end value using the negative Y value of the plane
  const planeEndYPosition = plane.transform.y.mul(-1).pinLastValue();

  // Create a timeDriver to set the duration of our animation
  const timeDriver = Animation.timeDriver({durationMilliseconds: 5000});
  // Create a linear sampler using the positions defined above as the start and end points
  let linearSampler = Animation.samplers.linear(planeInitialYPosition,planeEndYPosition);

  // Bind the Y position of the plane to an animation using the driver and sampler and
  // start the timeDriver
  plane.transform.y = Animation.animate(timeDriver,linearSampler);
  timeDriver.start();

  // Register a tap event on the plane
  TouchGestures.onTap(plane).subscribe(function() {
    // Redefine the linear sampler using the last Y value of the plane and the intial y value stored earlier
    linearSampler = Animation.samplers.linear(plane.transform.y.pinLastValue(), planeInitialYPosition);
    // Bind the Y position of the plane to an animation using the updated sampler and reset the time driver
    plane.transform.y = Animation.animate(timeDriver,linearSampler);
    timeDriver.reset();
  });