从父母传给孩子导致不必要的双向约束

Question

子组件根据父表中是否选择了记录从父项获取输入。在子组件中更新记录后，父级也会更新。我认为输入绑定是单向的？我试图仅更新子表的内容。  我已尝试将可观察数据传递给数组，然后返回到新的可观察数据，但这并没有起作用。

父组件：

    import { Component } from '@angular/core';
    import { MatTableDataSource } from '@angular/material';
    import { SelectionModel } from '@angular/cdk/collections';

    @Component({
      selector: 'app-root',
      templateUrl: './app.component.html',
      styleUrls: ['./app.component.css']
    })
    export class AppComponent {
      displayedColumns = ['select', 'position', 'name', 'weight', 'symbol'];
      dataSource = new MatTableDataSource<Element>(ELEMENT_DATA);
      selection = new SelectionModel<Element>(true, []);
      editReady: boolean = false;
      recordsToEdit: Array<Element> = [];

      /** Whether the number of selected elements matches the total number of rows. */
      isAllSelected() {
        const numSelected = this.selection.selected.length;
        const numRows = this.dataSource.data.length;
        return numSelected === numRows;
      }

      /** Selects all rows if they are not all selected; otherwise clear selection. */
      masterToggle() {
        this.isAllSelected() ?
          this.selection.clear() :
          this.dataSource.data.forEach(row => this.selection.select(row));
      }

      editRecords() {
        this.dataSource.data.forEach(row => {
          if (this.selection.isSelected(row) == true) {
            this.recordsToEdit.push(row);
          }
        }
        );
        this.editReady = !this.editReady;
      }
    }


    export interface Element {
      name: string;
      position: number;
      weight: number;
      symbol: string;
    }

    const ELEMENT_DATA: Element[] = [
      { position: 1, name: 'Hydrogen', weight: 1.0079, symbol: 'H' },
      { position: 2, name: 'Helium', weight: 4.0026, symbol: 'He' },
      { position: 3, name: 'Lithium', weight: 6.941, symbol: 'Li' },
      { position: 4, name: 'Beryllium', weight: 9.0122, symbol: 'Be' },
      { position: 5, name: 'Boron', weight: 10.811, symbol: 'B' },
      { position: 6, name: 'Carbon', weight: 12.0107, symbol: 'C' },
      { position: 7, name: 'Nitrogen', weight: 14.0067, symbol: 'N' },
      { position: 8, name: 'Oxygen', weight: 15.9994, symbol: 'O' },
      { position: 9, name: 'Fluorine', weight: 18.9984, symbol: 'F' },
      { position: 10, name: 'Neon', weight: 20.1797, symbol: 'Ne' },
      { position: 11, name: 'Sodium', weight: 22.9897, symbol: 'Na' },
      { position: 12, name: 'Magnesium', weight: 24.305, symbol: 'Mg' },
      { position: 13, name: 'Aluminum', weight: 26.9815, symbol: 'Al' },
      { position: 14, name: 'Silicon', weight: 28.0855, symbol: 'Si' },
      { position: 15, name: 'Phosphorus', weight: 30.9738, symbol: 'P' },
      { position: 16, name: 'Sulfur', weight: 32.065, symbol: 'S' },
      { position: 17, name: 'Chlorine', weight: 35.453, symbol: 'Cl' },
      { position: 18, name: 'Argon', weight: 39.948, symbol: 'Ar' },
      { position: 19, name: 'Potassium', weight: 39.0983, symbol: 'K' },
      { position: 20, name: 'Calcium', weight: 40.078, symbol: 'Ca' },
    ];

父视图：

        <div class="example-container mat-elevation-z8">
        <mat-table #table [dataSource]="dataSource">
        <!-- Checkbox Column -->
        <ng-container matColumnDef="select">
          <mat-header-cell *matHeaderCellDef>
            <mat-checkbox (change)="$event ? masterToggle() : null" [checked]="selection.hasValue() && isAllSelected()" [indeterminate]="selection.hasValue() && !isAllSelected()">
            </mat-checkbox>
          </mat-header-cell>
          <mat-cell *matCellDef="let row">
            <mat-checkbox (click)="$event.stopPropagation()" (change)="$event ? selection.toggle(row) : null" [checked]="selection.isSelected(row)">
            </mat-checkbox>
          </mat-cell>
        </ng-container>

        <!-- Position Column -->
        <ng-container matColumnDef="position">
          <mat-header-cell *matHeaderCellDef> No. </mat-header-cell>
          <mat-cell *matCellDef="let element"> {{element.position}} </mat-cell>
        </ng-container>

        <!-- Name Column -->
        <ng-container matColumnDef="name">
          <mat-header-cell *matHeaderCellDef> Name </mat-header-cell>
          <mat-cell *matCellDef="let element"> {{element.name}} </mat-cell>
        </ng-container>

        <!-- Weight Column -->
        <ng-container matColumnDef="weight">
          <mat-header-cell *matHeaderCellDef> Weight </mat-header-cell>
          <mat-cell *matCellDef="let element"> {{element.weight}} </mat-cell>
        </ng-container>

        <!-- Symbol Column -->
        <ng-container matColumnDef="symbol">
          <mat-header-cell *matHeaderCellDef> Symbol </mat-header-cell>
          <mat-cell *matCellDef="let element"> {{element.symbol}} </mat-cell>
        </ng-container>

        <mat-header-row *matHeaderRowDef="displayedColumns"></mat-header-row>
        <mat-row *matRowDef="let row; columns: displayedColumns;" (click)="selection.toggle(row)">
        </mat-row>
      </mat-table>
    </div>

    <br>
    <div>
      <button mat-raised-button (click)="editRecords()">Edit</button>
    </div>

    <br>
    <div *ngIf="editReady">
      <app-edit-data [editRecords]=" recordsToEdit"></app-edit-data>
    </div>

子视图：

    <div class="example-container mat-elevation-z8">
      <mat-table #table [dataSource]="dataSource">

        <!-- Checkbox Column -->
        <ng-container matColumnDef="select">
          <mat-header-cell *matHeaderCellDef>
            <mat-checkbox (change)="$event ? masterToggle() : null"
                          [checked]="selection.hasValue() && isAllSelected()"
                          [indeterminate]="selection.hasValue() && !isAllSelected()">
            </mat-checkbox>
          </mat-header-cell>
          <mat-cell *matCellDef="let row">
            <mat-checkbox (click)="$event.stopPropagation()"
                          (change)="$event ? selection.toggle(row) : null"
                          [checked]="selection.isSelected(row)">
            </mat-checkbox>
          </mat-cell>
        </ng-container>

        <!-- Position Column -->
        <ng-container matColumnDef="position">
          <mat-header-cell *matHeaderCellDef> No. </mat-header-cell>
          <mat-cell *matCellDef="let element"> {{element.position}} </mat-cell>
        </ng-container>

        <!-- Name Column -->
        <ng-container matColumnDef="name">
          <mat-header-cell *matHeaderCellDef> Name </mat-header-cell>
          <mat-cell *matCellDef="let element"> {{element.name}} </mat-cell>
        </ng-container>

        <!-- Weight Column -->
        <ng-container matColumnDef="weight">
          <mat-header-cell *matHeaderCellDef> Weight </mat-header-cell>
          <mat-cell *matCellDef="let element"> {{element.weight}} </mat-cell>
        </ng-container>

        <!-- Symbol Column -->
        <ng-container matColumnDef="symbol">
          <mat-header-cell *matHeaderCellDef> Symbol </mat-header-cell>
          <mat-cell *matCellDef="let element"> {{element.symbol}} </mat-cell>
        </ng-container>

        <mat-header-row *matHeaderRowDef="displayedColumns"></mat-header-row>
        <mat-row *matRowDef="let row; columns: displayedColumns;"
                 (click)="selection.toggle(row)">
        </mat-row>
      </mat-table>
    </div>

    <br>
    <div>
    <button mat-raised-button (click)="changeName()">Change Name</button>
    </div>

子组件：

    import { Component, OnInit, Input } from '@angular/core';
    import { MatTableDataSource } from '@angular/material';
    import { SelectionModel } from '@angular/cdk/collections';
    import { Element } from '../app.component'; 
    @Component({
      selector: 'app-edit-data',
      templateUrl: './edit-data.component.html',
      styleUrls: \['./edit-data.component.css'\]
    })
    export class EditDataComponent implements OnInit {
      @Input() editRecords: Array<Element>;
      dataSource = new MatTableDataSource<Element>();
      constructor() { }

      ngOnInit() {
        this.dataSource.data = this.editRecords;
      }

      displayedColumns = \['select', 'position', 'name', 'weight', 'symbol'\];
      selection = new SelectionModel<Element>(true, \[\]);

      /** Whether the number of selected elements matches the total number of rows. */
      isAllSelected() {
        const numSelected = this.selection.selected.length;
        const numRows = this.dataSource.data.length;
        return numSelected === numRows;
      }

      /** Selects all rows if they are not all selected; otherwise clear selection. */
      masterToggle() {
        this.isAllSelected() ?
          this.selection.clear() :
          this.dataSource.data.forEach(row => this.selection.select(row));
      }

      changeName() {
        this.dataSource.data.forEach(row => {
          if (this.selection.isSelected(row)) {
            row.name = "TEST";
          }
        });
      }

    }

Answer 1

这很有用。该数组保留了上述评论中提到的参考文献。

newArray = originalArray.map(x => Object.assign({}, x));

Source