javascript - 使用 null 值填充 FormGroup 并

Question

Chrome 控制台中出现错误:异常:错误:未捕获( promise 中):TypeError:无法读取 null 的属性“applicationName”。

型号: 导出类 BasicInfoModel {

    applicationName: string;
    localDirectoryPath: string; 
}

Controller 向父组件发送数据，父组件将数据保存到服务中。

Controller :

import { Component, Output, OnInit, EventEmitter} from '@angular/core';
import { FormGroup, FormControl, REACTIVE_FORM_DIRECTIVES, Validators,               
FormBuilder, FormArray}from "@angular/forms";
import { Observable } from "rxjs/Rx";
import { BasicInfoModel } from '../basicinfomodel';
import { BasicInfoService} from '../app.dev.basicinfo.service';

@Component({
   selector: 'basic-info',
   templateUrl: './basicInfo.html',
   styleUrls: ['../../ComponentStyles.css'],
   directives: [REACTIVE_FORM_DIRECTIVES]
})

export class BASIC_INFOComponent implements OnInit {

observableBasic: BasicInfoModel;
basicInfoForm: FormGroup;

@Output() basicInfoUpdate = new EventEmitter<JSON>();
@Output() basicInfoFormValid = new EventEmitter<Boolean>();

constructor(private formBuilder: FormBuilder, private BasicInfoService:      
BasicInfoService) {  }

onSubmit() {
    debugger;
    this.observableBasic;
    this.basicInfoUpdate.emit(this.basicInfoForm.value);
}

ngOnInit() {

    this.basicInfoForm = new FormGroup({
        'applicationName': new FormControl('', Validators.required),
        'localDirectoryPath': new FormControl('', Validators.required)
    });

    this.basicInfoForm.valueChanges.subscribe(data => console.log('form   
    changes', data));
    this.BasicInfoService.currentBasicInfo
        .subscribe(
        (basic: BasicInfoModel) => {
            this.observableBasic = basic;
        });

    (<FormGroup>this.basicInfoForm).setValue(this.observableBasic, { onlySelf: true });
}

}

我想要实现的目标:

1. 当我构建代码时，我希望我的 formGroup 应该填充空值。
2. 当我填写数据并将其保存到我的服务中的behaviorSubject时，稍后当我重新访问该页面时，我的formGroup应该与数据服务同步。

Answer 1

通过添加以下内容修改了 Controller :(this.observableBasic != undefined)

ngOnInit() {
    this.basicInfoForm = new FormGroup({
        'applicationName': new FormControl('', Validators.required),
        'localDirectoryPath': new FormControl('', Validators.required)
    });

    this.BasicInfoService.currentBasicInfo
        .subscribe((basic: BasicInfoModel) => { this.observableBasic = basic; });

    if (this.observableBasic != undefined) {
        (<FormGroup>this.basicInfoForm).setValue(this.observableBasic, { onlySelf: true });
    }      

    this.basicInfoForm.valueChanges.subscribe(data => console.log('form changes', data));
}