update histogram when data changes (for phet-io), see #42

js/coins/model/CoinsExperimentSceneModel.ts

@@ -29,6 +29,8 @@ type SelfOptions = {
 };
 type CoinExperimentSceneModelOptions = SelfOptions & PickRequired<PhetioObjectOptions, 'tandem'>;
 
+type MeasuredCoinStates = ClassicalCoinStates | QuantumCoinStates;
+
 // constants
 
 // allowed values for the number of coins to use in the multi-coin experiment
@@ -51,7 +53,7 @@ export default class CoinsExperimentSceneModel extends PhetioObject {
   // The coins that are flipped/prepared and then measured during the experiment.
   public readonly singleCoin: TwoStateSystem<ClassicalCoinStates> | TwoStateSystem<QuantumCoinStates>;
 
-  public readonly coinSet: TwoStateSystemSet<ClassicalCoinStates | QuantumCoinStates>;
+  public readonly coinSet: TwoStateSystemSet<ClassicalCoinStates> | TwoStateSystemSet<QuantumCoinStates>;
 
   // The initial state of the coin(s) before any flipping or other experiment preparation occurs.
   public readonly initialCoinStateProperty: Property<ClassicalCoinStates> | Property<QuantumUncollapsedCoinStates>;
@@ -136,11 +138,10 @@ export default class CoinsExperimentSceneModel extends PhetioObject {
 
         // The scene is moving from preparation mode to measurement mode. Set the coins to be in the initial state
         // chosen by the user.  If these are quantum coins and the initial state is set to superposed, set an arbitrary
-        // initial state, which is okay because the values won't be shown to the user.
-        let initialState = this.initialCoinStateProperty.value;
-        if ( this.systemType === 'quantum' && initialState === 'superposed' ) {
-          initialState = 'up';
-        }
+        // initial state.  This is okay because the values won't be shown to the user.
+        const initialState: MeasuredCoinStates = this.initialCoinStateProperty.value === 'superposed' ?
+                                                 'up' :
+                                                 this.initialCoinStateProperty.value;
         // TODO: How can this be better and avoid the "as never" weirdness?  See https://github.com/phetsims/quantum-measurement/issues/42.
         this.singleCoin.setMeasurementValuesImmediate( initialState as never );
         this.coinSet.setMeasurementValuesImmediate( initialState as never );

js/common/model/TwoStateSystem.ts

@@ -14,15 +14,14 @@ import TwoStateSystemSet, { TwoStateSystemSetOptions } from './TwoStateSystemSet
 import StrictOmit from '../../../../phet-core/js/types/StrictOmit.js';
 import Property from '../../../../axon/js/Property.js';
 import StringUnionIO from '../../../../tandem/js/types/StringUnionIO.js';
-import NullableIO from '../../../../tandem/js/types/NullableIO.js';
 
 type SelfOptions = EmptySelfOptions;
 type TwoStateSystemOptions = SelfOptions & StrictOmit<TwoStateSystemSetOptions, 'maxNumberOfSystems'>;
 
 export default class TwoStateSystem<T extends string> extends TwoStateSystemSet<T> {
 
   // the value of most recent measurement, null indicates indeterminate
-  public readonly measuredValueProperty: Property<T | null>;
+  public readonly measuredValueProperty: Property<T>;
 
   public constructor( stateValues: readonly T[],
                       initialState: T,
@@ -37,8 +36,8 @@ export default class TwoStateSystem<T extends string> extends TwoStateSystemSet<
 
     this.measuredValueProperty = new Property( initialState, {
       tandem: options.tandem.createTandem( 'measuredValueProperty' ),
-      phetioValueType: NullableIO( StringUnionIO( stateValues ) ),
-      validValues: [ ...stateValues, null ]
+      phetioValueType: StringUnionIO( stateValues ),
+      validValues: [ ...stateValues ]
     } );
 
     // Hook up to the data-changed emitter to update the data Property.

js/common/model/TwoStateSystemSet.ts

@@ -33,7 +33,7 @@ export type TwoStateSystemSetOptions = SelfOptions & PickRequired<PhetioObjectOp
 
 export type StateSetMeasurementResult<T> = {
   length: number;
-  measuredValues: Array<T | null>;
+  measuredValues: Array<T>;
 };
 
 // Define the time that it will take to prepare a measurement, in seconds.  This is empirically determined.
@@ -267,7 +267,7 @@ export default class TwoStateSystemSet<T extends string> extends PhetioObject {
    * Set the measurement values immediately to the provided value for all elements in this set without transitioning
    * through the 'preparingToBeMeasured' state.
    */
-  public setMeasurementValuesImmediate( value: T ): void {
+  public setMeasurementValuesImmediate( whatIsUpHere: T ): void {
 
     // Cancel any in-progress preparation.
     if ( this.preparingToBeMeasuredTimeoutListener ) {
@@ -276,7 +276,7 @@ export default class TwoStateSystemSet<T extends string> extends PhetioObject {
     }
 
     // Set the seed value to the value that will incite its listener to update the data to the provided value.
-    const valueIndex = this.validValues.indexOf( value );
+    const valueIndex = this.validValues.indexOf( whatIsUpHere );
     assert && assert( valueIndex === 0 || valueIndex === 1 );
     this.seedProperty.value = valueIndex;