下拉菜单不使用Angular中的API数据填充

Question

我想从api中检索下拉列表中的数据，但我不知道我的代码中出了什么问题。

API结果：

[{"projectId":2,"projectName":"test","gates":[]},{"projectId":3,"projectName":"project1","gates":[]}]

服务模型(项目.ts(：

export class Project{
projectName: string;
projectId :number;
}

我的侧边栏.component.html中的下拉菜单：

<div class="dropdown  ml-auto">
<select (change)=selectedHandlerProjectName($event) class="btn btn-secondary dropdown-toggle" style="margin-left: -10px;border-left-width:15px;padding-left:11px;padding-right: 14px;margin-right: 12px;border-right-width: 12px">
<option value = "default">Select project</option>
<option *ngFor = "let projectName of selectProject?.projectName" value = {{projectName}}>{{projectName}}</option>
</select>
</div>

边栏组件.ts

import { Component, OnInit } from '@angular/core';
import { Project } from '../models/Project';
import {ProjectService} from '../services/project.service';
@Component({
selector: 'app-sidebar',
templateUrl: './sidebar.component.html',
styleUrls: ['./sidebar.component.css']
})
export class SidebarComponent implements OnInit {
selectProject : Project;
constructor(private projectService: ProjectService) { }
getSelectedProject(): void{  
this.projectService.getProjects()
.subscribe(selectProject => this.selectProject= selectProject);
}
//methods to get dropdown values
dropDownProjectName: string = '';
selectedHandlerProjectName(event : any)
{
if(event.target.value != 'default') { this.dropDownProjectName = event.target.value;}
else {this.dropDownProjectName = null;}
}
ngOnInit() {
this.getSelectedProject();
}
}

Project.service.ts

import { Injectable } from '@angular/core';
import { Observable, of } from 'rxjs';
import { HttpClient,HttpHeaders } from '@angular/common/http';
import {catchError,map,tap} from 'rxjs/operators';
import { Project } from '../models/Project';
import { environment } from '../../environments/environment';
@Injectable({
providedIn: 'root'
})
export class ProjectService {
private urlProject = environment.baseUrl + environment.urlProject ;
constructor(private http: HttpClient) { }
getProjects(): Observable<any>{
return this.http.get<Project>(this.urlProject)
.pipe(
catchError(this.handleError('getProject',[]))
);
} 
}

当应用程序运行时，如果我在网络中查看，则显示API中的数据，但不显示在下拉列表中。

Answer 1

只需尝试用html下拉代码替换它。它会起作用的。因为您不需要在*ngFor、*ngFor = "let projectName of selectProject?.projectName"中检查productName

<select class="btn btn-secondary dropdown-toggle" >
<option value="default">Select project</option>
<option *ngFor="let project of selectProject" [value]="project.projectName">{{project.projectName}}</option>
</select>