Angular 8：未使用反应形式在组件中选择下拉列表值

Question

我正在动态填充下拉列表及其值。当我单击“提交”按钮后，选择了所有值后，无法在表单中设置其值，我得到的是空白值。

HTML：

<div class="col-md-6" *ngFor="let type of types">
                        <div class="form-group">
                            <label>Select {{ type.cat_name }}</label>
                            <select class="form-control custom-select" 
                                (change)="onChangeType($event.target.value)"
                                [value]="type.key_name" >
                                <option value="">-- Select --</option>
                                <ng-container *ngFor="let subType of dynamicCategoryData">
                                    <option *ngIf="subType.key == type.key_name" [value]="subType.value">{{subType.value}}</option>
                                </ng-container>
                            </select>
                        </div>
                    </div>

component.ts

  ngOnInit() {
    this.uploadArtWorkForm = this.formBuilder.group({
      thumb_img: ['', [Validators.required]],
      categoryArray: this.formBuilder.array([]),
    });

  }

addUploadArtWorkForm() {
    console.log("this.uploadArtWorkForm.value", this.uploadArtWorkForm.value)
}

输出：

{
    "categoryArray": [
        {
            "gems": null,
            "metal": null,
            "type": null
        }
    ]
}

仅仅是因为我没有使用formControlName吗？没有它，我们可以做到吗？

任何帮助将不胜感激。

Answer 1

如下修改您的app.component.html：

<div class="col-md-6" formArrayName="categoryArray" *ngIf="uploadArtWorkForm.get('categoryArray')['controls'].length > 0">
        <div  *ngFor="let item of uploadArtWorkForm.get('categoryArray')['controls']; let k = index">
            <div [formGroup]="item">
                <div class="form-group ">
                    <label>Select {{ types[k].cat_name }}</label>
                    <select class="form-control custom-select" [class]="types[k].key_name" (change)="onChangeType($event.target.value)" formControlName="{{ types[k].key_name }}" *ngIf="types[k].cat_name == 'Type'"> 
              <option value="">-- Select --</option>
              <option *ngFor="let type of catTypeValue" [value]="type.cat_name">
                  {{type.cat_name}}
              </option>
          </select>
          <select class="form-control custom-select" [class]="types[k].key_name" (change)="onChangeType($event.target.value)" formControlName="{{ types[k].key_name }}" *ngIf="types[k].cat_name == 'Metal'">
              <option value="">-- Select --</option>
              <option *ngFor="let type of catMetalValue" [value]="type.category_id">
                  {{type.cat_name}}
              </option>
          </select>
          <select class="form-control custom-select" [class]="types[k].key_name" (change)="onChangeType($event.target.value)" formControlName="{{ types[k].key_name }}" *ngIf="types[k].cat_name == 'Gems'">
              <option value="">-- Select --</option>
              <option *ngFor="let type of catGemsValue" [value]="type.category_id">
                  {{type.cat_name}}
              </option>
          </select>
                </div>
            </div>
        </div>
    </div>

和以下app.component.ts：

  onChangeType(value, id){
    console.log(value);
  }
  onChangeCategory(event, id) {
    if (id) {
      this.types = [
        {"parent_id":1,
        "cat_name":"Type",
        "category_id":2,
        "key_name":"type"},
        {"parent_id":1,
        "cat_name":"Metal",
        "category_id":14,
        "key_name":"metal"},
        {"parent_id":1,
        "cat_name":"Gems",
        "category_id":15,
        "key_name":"gems"}];
      if(this.uploadArtWorkForm.controls['categoryArray'].length > 0){
        this.uploadArtWorkForm.controls['categoryArray'].controls.length = 0
      }
      this.addInNewCategory(this.types);
    } else {
      this.types = null;
      this.subTypes = null;
    }
  }

  get category(): FormArray {
    return <FormArray>this.uploadArtWorkForm.controls['categoryArray'];
  }

  addInNewCategory(types) {['categoryArray'];
    types.forEach((element, i) => {
      this.category.push(this.formBuilder.group({[element["key_name"]]: new FormControl(element["key_name"])
      }));
    });
  }
}