From 103b83ebafccb595799879292b8d660ba6634383 Mon Sep 17 00:00:00 2001
From: Sam Reid <reids@colorado.edu>
Date: Thu, 3 Mar 2022 21:06:13 -0700
Subject: [PATCH] Convert method to emitter, see
 https://github.com/phetsims/center-and-spread/issues/45

---
 js/common/model/CASModel.ts    | 15 +++++++++------
 js/common/model/SoccerModel.ts | 25 ++++++++++++-------------
 2 files changed, 21 insertions(+), 19 deletions(-)

diff --git a/js/common/model/CASModel.ts b/js/common/model/CASModel.ts
index 39e7348d..dbe502b7 100644
--- a/js/common/model/CASModel.ts
+++ b/js/common/model/CASModel.ts
@@ -71,6 +71,9 @@ class CASModel {
   private lastHighlightAnimationStepTime: number;
   readonly isMedianAnimationCompleteProperty: BooleanProperty;
 
+  // TODO: See if TypeScript 4.6 will let us initialize more things here
+  protected readonly objectValueBecameNonNullEmitter: Emitter<[ CASObject ]>;
+
   constructor( objectType: CASObjectType, maxNumberOfObjects: number, providedOptions: CASModelOptions ) {
 
     const options = optionize<CASModelOptions, CASModelSelfOptions, {}>( {
@@ -176,7 +179,7 @@ class CASModel {
           if ( options.includeCards ) {
             this.cardModelGroup.createNextElement( casObject );
           }
-          this.objectValueBecameNonNull( casObject );
+          this.objectValueBecameNonNullEmitter.emit( casObject );
           casObject.valueProperty.unlink( listener ); // Only create the card once, then no need to listen further
         }
       };
@@ -214,6 +217,11 @@ class CASModel {
         this.isMedianAnimationCompleteProperty.value = false;
       }
     } );
+
+    this.objectValueBecameNonNullEmitter = new Emitter<[ CASObject ]>( {
+      parameters: [ { valueType: CASObject } ]
+    } );
+    this.objectValueBecameNonNullEmitter.addListener( () => this.updateAnimation() );
   }
 
   updateMeanAndMedian(): void {
@@ -336,11 +344,6 @@ class CASModel {
     } );
   }
 
-  // TODO: Should this be an emitter?  We say yes.
-  protected objectValueBecameNonNull( casObject: CASObject ): void {
-    this.updateAnimation();
-  }
-
   /**
    * Clears out the data and the cards
    */
diff --git a/js/common/model/SoccerModel.ts b/js/common/model/SoccerModel.ts
index 74cd0b20..05635b5a 100644
--- a/js/common/model/SoccerModel.ts
+++ b/js/common/model/SoccerModel.ts
@@ -97,6 +97,18 @@ class SoccerModel extends CASModel {
       numberOfRemainingKickableObjects => numberOfRemainingKickableObjects > 0 );
 
     this.currentDistribution = SoccerModel.chooseDistribution();
+
+    this.objectValueBecameNonNullEmitter.addListener( casObject => {
+
+      // If the soccer player that kicked that ball was still in line when the ball lands, they can leave the line now.
+      if ( this.soccerPlayerGroup.includes( this.ballPlayerMap.get( casObject )! ) ) {
+        this.advanceLine();
+      }
+
+      if ( this.numberOfRemainingObjectsProperty.value > 0 && this.nextBallToKickProperty.value === null ) {
+        this.nextBallToKickProperty.value = this.createBall();
+      }
+    } );
   }
 
   static chooseDistribution(): number[] {
@@ -267,19 +279,6 @@ class SoccerModel extends CASModel {
     }
   }
 
-  protected objectValueBecameNonNull( casObject: CASObject ): void {
-    super.objectValueBecameNonNull( casObject );
-
-    // If the soccer player that kicked that ball was still in line when the ball lands, they can leave the line now.
-    if ( this.soccerPlayerGroup.includes( this.ballPlayerMap.get( casObject )! ) ) {
-      this.advanceLine();
-    }
-
-    if ( this.numberOfRemainingObjectsProperty.value > 0 && this.nextBallToKickProperty.value === null ) {
-      this.nextBallToKickProperty.value = this.createBall();
-    }
-  }
-
   // When a ball lands, or when the next player is supposed to kick (before the ball lands), move the line forward
   private advanceLine(): void {