feat(popover-edit): Helper class to reduce form state preservation boilerplate (#15939)

src/cdk-experimental/popover-edit/form-value-container.ts

@@ -0,0 +1,38 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+export interface Entry<FormValue> {
+  value?: FormValue;
+}
+
+/**
+ * A convenience class for preserving unsaved form state while an edit lens is closed.
+ *
+ * Example usage:
+ * class MyComponent {
+ *   readonly nameEditValues = new FormValueContainer&lt;Item, {name: string}&gt;();
+ * }
+ *
+ * &lt;form cdkEditControl [(cdkEditControlPreservedFormValue)]="nameEditValues.for(item).value"&gt;
+ */
+export class FormValueContainer<Key extends object, FormValue> {
+  private _formValues = new WeakMap<Key, Entry<FormValue>>();
+
+  for(key: Key): Entry<FormValue> {
+    const _formValues = this._formValues;
+
+    let entry = _formValues.get(key);
+    if (!entry) {
+      // Expose entry as an object so that we can [(two-way)] bind to its value member
+      entry = {};
+      _formValues.set(key, entry);
+    }
+
+    return entry;
+  }
+}

src/cdk-experimental/popover-edit/popover-edit.spec.ts

@@ -14,6 +14,7 @@ import {
   CdkPopoverEditColspan,
   CdkPopoverEditModule,
   HoverContentState,
+  FormValueContainer,
   PopoverEditClickOutBehavior,
 } from './index';
 
@@ -22,8 +23,7 @@ const NAME_EDIT_TEMPLATE = `
       <form #f="ngForm"
           cdkEditControl
           (ngSubmit)="onSubmit(element, f)"
-          [cdkEditControlPreservedFormValue]="preservedValues.get(element)"
-          (cdkEditControlPreservedFormValueChange)="preservedValues.set(element, $event)"
+          [(cdkEditControlPreservedFormValue)]="preservedValues.for(element).value"
           [cdkEditControlIgnoreSubmitUnlessValid]="ignoreSubmitUnlessValid"
           [cdkEditControlClickOutBehavior]="clickOutBehavior">
         <input [ngModel]="element.name" name="name" required>
@@ -63,7 +63,7 @@ interface PeriodicElement {
 abstract class BaseTestComponent {
   @ViewChild('table', {static: false}) table: ElementRef;
 
-  preservedValues = new Map<number, PeriodicElement>();
+  preservedValues = new FormValueContainer<PeriodicElement, {'name': string}>();
 
   ignoreSubmitUnlessValid = true;
   clickOutBehavior: PopoverEditClickOutBehavior = 'close';

src/cdk-experimental/popover-edit/public-api.ts

@@ -9,6 +9,7 @@
 export * from './edit-event-dispatcher';
 export * from './edit-ref';
 export * from './focus-dispatcher';
+export * from './form-value-container';
 export * from './lens-directives';
 export * from './popover-edit-module';
 export * from './popover-edit-position-strategy-factory';

src/material-examples/popover-edit-mat-table/popover-edit-mat-table-example.html

@@ -8,8 +8,7 @@
       <form #f="ngForm"
           matEditLens
           (ngSubmit)="onSubmitWeight(element, f)"
-          [matEditLensPreservedFormValue]="preservedWeightValues.get(element)"
-          (matEditLensPreservedFormValueChange)="preservedWeightValues.set(element, $event)">
+          [(matEditLensPreservedFormValue)]="weightValues.for(element).value">
         <div mat-edit-content>
           <mat-form-field>
             <input matInput type="number" [ngModel]="element.weight" name="weight" required>
@@ -50,8 +49,7 @@
           <form #f="ngForm"
               matEditLens
               (ngSubmit)="onSubmitName(element, f)"
-              [matEditLensPreservedFormValue]="preservedNameValues.get(element)"
-              (matEditLensPreservedFormValueChange)="preservedNameValues.set(element, $event)">
+              [(matEditLensPreservedFormValue)]="nameValues.for(element).value">
             <h2 mat-edit-title>Name</h2>
             <div mat-edit-content>
               <mat-form-field>

src/material-examples/popover-edit-mat-table/popover-edit-mat-table-example.ts

@@ -1,5 +1,6 @@
 import {Component} from '@angular/core';
 import {DataSource} from '@angular/cdk/collections';
+import {FormValueContainer} from '@angular/cdk-experimental/popover-edit';
 import {NgForm} from '@angular/forms';
 import {MatSnackBar} from '@angular/material/snack-bar';
 import {BehaviorSubject, Observable} from 'rxjs';
@@ -46,8 +47,8 @@ export class PopoverEditMatTableExample {
   displayedColumns: string[] = ['position', 'name', 'weight', 'symbol'];
   dataSource = new ExampleDataSource();
 
-  readonly preservedNameValues = new WeakMap<PeriodicElement, any>();
-  readonly preservedWeightValues = new WeakMap<PeriodicElement, any>();
+  readonly nameValues = new FormValueContainer<PeriodicElement, any>();
+  readonly weightValues = new FormValueContainer<PeriodicElement, any>();
 
   constructor(private readonly _snackBar: MatSnackBar) {}
 

src/material-experimental/popover-edit/popover-edit.spec.ts

@@ -12,6 +12,7 @@ import {BehaviorSubject} from 'rxjs';
 import {
   CdkPopoverEditColspan,
   HoverContentState,
+  FormValueContainer,
   PopoverEditClickOutBehavior,
 } from '@angular/cdk-experimental/popover-edit';
 import {MatPopoverEditModule} from './index';
@@ -21,8 +22,7 @@ const NAME_EDIT_TEMPLATE = `
       <form #f="ngForm"
           matEditLens
           (ngSubmit)="onSubmit(element, f)"
-          [matEditLensPreservedFormValue]="preservedValues.get(element)"
-          (matEditLensPreservedFormValueChange)="preservedValues.set(element, $event)"
+          [(matEditLensPreservedFormValue)]="preservedValues.for(element).value"
           [matEditLensIgnoreSubmitUnlessValid]="ignoreSubmitUnlessValid"
           [matEditLensClickOutBehavior]="clickOutBehavior">
         <input [ngModel]="element.name" name="name" required>
@@ -62,7 +62,7 @@ interface PeriodicElement {
 abstract class BaseTestComponent {
   @ViewChild('table', {static: false}) table: ElementRef;
 
-  preservedValues = new Map<number, PeriodicElement>();
+  preservedValues = new FormValueContainer<PeriodicElement, {'name': string}>();
 
   ignoreSubmitUnlessValid = true;
   clickOutBehavior: PopoverEditClickOutBehavior = 'close';