我想要用来自服务器的数据填充页面，并且能够更改信息，为此，我使用 formbuilder 将来自服务器的数据作为默认值使用：

 createForm(){
    this.getGeral()
    this.getTiposTarefas()
    this.formulario = this.fb.group({
      'tipo_tarefa':[this.tarefa.tipoTarefa.id, Validators.compose([Validators.required])], // Cant set default values cuz the array is object is undefined
      'data_tarefa': [this.tarefa.data_tarefa, Validators.compose([Validators.required])],// Cant set default values cuz the array is object is undefined
      'inicio_tarefa': [this.tarefa.inicio, Validators.compose([Validators.required])],// Cant set default values cuz the array is object is undefined
      'fim_tarefa': [this.tarefa.fim, Validators.compose([Validators.required])]// Cant set default values cuz the array is object is undefined
   });
  }

但是它未定义。我在订阅函数中尝试了 console.log()，并且对象“Tarefa”已填充，但在函数范围之外则没有。

    import { Component, OnInit } from '@angular/core';
    import { NavParams, ModalController } from '@ionic/angular';
    import { TarefadetalheService } from './tarefadetalhe.service';
    import { Tarefa } from '../../models/tarefa.model';
    import { TipoTarefa } from '../../models/tipotarefa.model';

    import { FormGroup, FormBuilder, Validators } from '@angular/forms';
    @Component({
      selector: 'app-tarefas-detalhe',
      templateUrl: './tarefas-detalhe.page.html',
      styleUrls: ['./tarefas-detalhe.page.scss'],
    })
    export class TarefasDetalhePage implements OnInit {
     idTarefa = null
     tarefa: Tarefa
     tiposTarefas : TipoTarefa[]
     formulario: FormGroup
      constructor(
        private navParams: NavParams,
        private getTarefaDetalhe: TarefadetalheService,
        private modalController:ModalController,
        public fb: FormBuilder) {   }

      ngOnInit() {

        this.createForm()
      }

      getGeral(){
        this.idTarefa = this.navParams.get('id_tarefa');
        this.getTarefaDetalhe.recuperaDetalhes().subscribe((data: Tarefa)=>{ //passar o id da tarefa como parametro no recupera detalhes
        this.tarefa = data
       })
      }

  getTiposTarefas(){
    this.getTarefaDetalhe.recuperaTiposTarefas().subscribe((data: TipoTarefa[])=>{
    this.tiposTarefas = data
    console.log(this.tiposTarefas) // here it has information
    })
    console.log(this.tiposTarefas) // here it has not information
  }

  createForm(){
    this.getGeral()
    this.getTiposTarefas()
    this.formulario = this.fb.group({
      'tipo_tarefa':[this.tarefa.tipoTarefa.id, Validators.compose([Validators.required])], // Cant set default values cuz the array is object is undefined
      'data_tarefa': [this.tarefa.data_tarefa, Validators.compose([Validators.required])],// Cant set default values cuz the array is object is undefined
      'inicio_tarefa': [this.tarefa.inicio, Validators.compose([Validators.required])],// Cant set default values cuz the array is object is undefined
      'fim_tarefa': [this.tarefa.fim, Validators.compose([Validators.required])]// Cant set default values cuz the array is object is undefined
   });
  }
 closeModal()
 {
   this.modalController.dismiss();
 }
}

当我运行 Ionic serve 时，它​​会抛出以下错误，并且我无法在表单控件上设置默认值：

我的 HTML：

<ion-content padding *ngIf="tarefa != null">
  <form [formGroup]="formulario">
    <h4>
      <ion-icon name="list-box"></ion-icon> Geral
    </h4>
    <ion-grid>
      <ion-row>
        <ion-col size="8">
            <ion-label position="floating">Tipo de Tarefa</ion-label>
          <ion-select [formControlName]="tipo_tarefa" okText="Confirmar" cancelText="Cancelar">
            <ion-select-option *ngFor="let tipo of tiposTarefas" [value]="tipo.id">{{tipo.descricao}}</ion-select-option>
          </ion-select>
        </ion-col>
      </ion-row>
    </ion-grid>
    <h4>
      <ion-icon name="calendar"></ion-icon> Horário
    </h4>
    <ion-item-divider></ion-item-divider>
    <ion-grid>
      <ion-row>
        <ion-col size="5">
          <ion-label position="stacked">Data</ion-label>
          <ion-datetime  [formControlName]="data_tarefa" display-format="DD-MM-YYYY" max="2050-10-31" picker-format="DD-MM-YYYY"></ion-datetime>
        </ion-col>
        <ion-col size="3">
          <ion-label position="stacked">Inicio</ion-label>
          <ion-datetime  [formControlName]="inicio_tarefa" display-format="HH:mm" picker-format="HH:mm" ></ion-datetime>
        </ion-col>
        <ion-col size="3">
          <ion-label position="stacked">Fim</ion-label>
          <ion-datetime  [formControlName]="fim_tarefa" display-format="HH:mm" picker-format="HH:mm"></ion-datetime>
        </ion-col>
      </ion-row>
    </ion-grid>
    <h4>
      <ion-icon name="person"></ion-icon> Cliente
    </h4>
    <ion-item-divider></ion-item-divider>
    <ion-grid>
      <ion-row>
      </ion-row>
    </ion-grid>
  </form>
</ion-content>