A brief analysis of how to use FormArray and modal boxes in Angular

How to use FormArray and modal box together? The following article will introduce to you how to use Angular's FormArray and modal box together. I hope it will be helpful to you!

Business scenario

Use FormArray to create dynamic forms. Every time a form is created, a new input is added to the page to display the title of the form. Click Edit and jump to click the fill-in content of the form. [Related tutorial recommendations: "angular tutorial"]

    // 封装获取modelList
    get modelList() {
        return this.formGroup.get('modelList') as FormArray
    }
    constructor(private fb: FormBuilder) {}
    ngOnInit() {
        // 一开始初始化arr为空数组
        this.formGroup = this.fb.group({
            // 内部嵌套FormControl、FormArray、FormGroup
            modelList: this.fb.array([])
        })
    }
    // 模态框构造内部的表单
    function newModel() {
        return this.fb.group({
            modelName: [''],
            // 可以继续嵌套下去，根据业务需求
        })
    }
    // 省略模态框部分代码
    // 传递到模态框的FormArray
    selectedType: FormArray

Form list

Form Details [Modal Box]

<form [FormGroup]="formGroup">
    <div FormArrayName="modelList">
        <ng-container *nfFor="let item of modelList.controls;let i = index" [FormGroupName]="i">
            <nz-input-group
                [nzSuffix]="suffixIconSearch"
              >
                <input type="text" nz-input formControlName="modelName"/>
              </nz-input-group>
              <ng-template #suffixIconSearch>
                <span
                  nz-icon
                  nzType="edit"
                  class="hover"
                  (click)="showModal(i)"
                ></span>
              </ng-template>
        </ng-container>
    </div>
</form>
<nz-modal
  [(nzVisible)]="isVisible"
  nzTitle="Model"
  [nzFooter]="modalFooter"
  (nzOnCancel)="handleCancel()"
  (nzOnOk)="handleOk()"
>
  <ng-container *nzModalContent>
    <form nz-form [formGroup]="selectedType">
      <nz-form-item>
        <nz-form-label nzRequired>Model Test</nz-form-label>
        <nz-form-control>
          <input
            type="text"
            nz-input
            placeholder="请输入ModelName"
            formControlName="modelName"
          />
        </nz-form-control>
      </nz-form-item>
      <nz-form-item>
        <nz-form-control>
          <product-config></product-config>
        </nz-form-control>
      </nz-form-item>
    </form>
  </ng-container>
  <ng-template #modalFooter>
    <button *ngIf="!isNewModel" nzDanger nz-button nzType="default" (click)="handleDelete()">删除</button>
    <button *ngIf="isNewModel" nz-button nzType="default" (click)="handleCancel()">取消</button>
    <button nz-button nzType="primary" (click)="handleOk()">保存</button>
  </ng-template>
</nz-modal>

Because this kind of modal box is special, it separates the relationship between the FormGroup of the form and needs to be passed when clicking. The parameters are sent to the modal box to display part of the value. If you simply pass the parameters and use this.modelList.at(index) to obtain the entity and assign the value to the modal box for modification, you will find the modification after clicking Save in the modal box. The value is not updated in the form, and modifications to the input value on the form are found to affect the content of the modal box.

But the form added by the modal box can be responded to the page.

Original error code idea

• After clicking edit, pass the clicked FormArray element to a temporary variable this.selectedType = <FormGroup>this.modelList.at(index);, and pass the value to the modal box form.

• Click to save the modal box and replace the original FormArray value again

this.modelList.removeAt(this.modelIndex)
this.modelList.insert(this.modelIndex, this.selectedType)

---

• ##Click to add , create a new FormGroup object

• Save and add push to the FormArray of the original page

newModelType(): FormGroup {
    return this.fb.group({
      modelName: ['', Validators.required],
      configList: this.fb.array([]),
    });
  }
// ...省略
// 模态框显示
show() {
    this.isVisible = true
    this.selectedType = this.newModelType();
}
// 保存
save() {
    this.isVisible = false
    // 原页面FormArray
    this.modelList.push(this.selectedType);
}

Finally found that this writing method can only be used in one direction Change, the modified value of the input outside the page will affect the modal box, but the value of the modal box is changed and saved, but the outside is not updated. Checking the internal parameters of the FormArray of the page through the console method found that there were actually changes, but Angular did not detect it. At this time, it is judged that the reason why there is no response is generally that the angular detection mechanism is not triggered. After carefully checking the document, I found that there is a very important line

angular document at the bottom that says

When I first read it, I felt that I followed this principle, because when editing, I chose to manipulate the original FormArray to delete and insert elements, which followed this rule, but in fact, in the modal box Assignment already violates this principle. When assigning value, I took the element instance of FormArray and assigned it to the temporary variable of the modal box, then changed the value of the instance, and deleted the insertion again. Essentially, I was operating the same instance. So angular did not detect the change [although the value changed]

So what is the correct approach? ?

Don't be lazy when assigning values. You still have to re-create a new object and then get the assigned value of the original object. [Equivalent to deep copy]

      this.selectedType = this.newModelType();
      const old = this.modelList.at(index);
      this.selectedType.setValue({
        'modelName': old.get('modelName').value
    })

You can update normally at this time.

Summary

In fact, in the end, it was essentially a return to the document. There are also many pitfalls in troubleshooting errors, and there are basically no angular articles in China, so we have to rely on external forums to find problems.

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