如何在 Reactive Forms 中将 Select 中的当前年份设置为默认值？答案

【问题标题】：How do I set the current year in my Select as default in Reactive Forms?如何在 Reactive Forms 中将 Select 中的当前年份设置为默认值？
【发布时间】：2020-04-25 14:26:25
【问题描述】：

您好，我创建了一个选择，显示当前年份、过去 5 年和未来 3 年。现在我想设置它，以便当前年份始终是默认值。这应该在反应形式中完成......你知道怎么做吗？

我的代码：

// HTML
<form [formGroup]="sendYearsForm">
<select class="upload_slc" id="upload_slc" required title="" formControlName="year" 
 (change)="sendYear($event)">
   <option *ngFor="let years of sendYears" [value]="years">{{years}}</option>
</select>
 <div class="select_arrow"></div>
</form>

// TS
sendYearsForm: FormGroup;
currentDate: Date = new Date();
selectedYear: number;

// Year form
    this.sendYearsForm = this.fb.group({
      year: [null]
    });
    // Show the current year with -5 and +3
    this.selectedYear = this.currentDate.getFullYear(); // HThe current year is transferred here. How do I integrate it into the template?
    for (let i = this.currentDate.getFullYear() - 5; i <= this.currentDate.getFullYear() + 3; i++) {
      this.sendYears.push(i);
    }

【问题讨论】：

标签： javascript angular typescript angular-material dropdown

【解决方案1】：

您可以使用 patchValue 来更改表单控件的值

yourFormGroupName.controls.yourFormControlName.patchValue（您要分配的值）

你的情况

this.sendYearsForm = this.fb.group({
  year: [null]
});
// Show the current year with -5 and +3
this.selectedYear = this.currentDate.getFullYear(); // The current year is transferred here. How do I integrate it into the template?

this.sendYearsForm.controls.year.patchValue(this.selectedYear); // this will set the value of 'year' control to selectedYear(current year)

for (let i = this.currentDate.getFullYear() - 5; i <= this.currentDate.getFullYear() + 3; i++) {
  this.sendYears.push(i);
}

【讨论】：

谢谢。完美答案:)

【解决方案2】：

您可以通过以下方式之一进行操作：

this.selectedYear = this.currentDate.getFullYear();
this.sendYearsForm= this.fb.group({
  year: new FormControl(this.selectedYear, [])
});

或

this.sendYearsForm = this.fb.group({
 year: [null]
});
this.selectedYear = this.currentDate.getFullYear();
this.sendYearsForm.get('year').setValue(this.selectedYear);

【讨论】：