订阅后服务价值仍未定义

Question

我有一个函数，一旦用户在表单中选择一个值就会调用它：

onChange($x: any){
  this.ApiService
      .getCarsByManufacturer($x.target.value)
      .subscribe(data => this.carListAfterManufacturerSelect = data);
  console.log(this.carListAfterManufacturerSelect)
}

服务：

getCarsByManufacturer(manufacturer: string): Observable<Cars[]>{
    return this.http.get<Cars[]>(this.apiBaseUrl + '/cars/spec/' + manufacturer)
  }

我想将用户选择的值用作我的函数的参数，但 carListAfterManufacturerSelect 一直返回 undefined。有什么建议吗？

Answer 1

订阅的工作原理如下：

onChange($x: any){
  this.ApiService.getCarsByManufacturer($x.target.value).subscribe(data => {
    this.carListAfterManufacturerSelect = data;
    console.log('2. Received !', this.carListAfterManufacturerSelect); // filled
    this.codeToBeExecutedAfterHttpCallIsReceived()
  });
  console.log('1. Not received yet', this.carListAfterManufacturerSelect); // undefined
}

codeToBeExecutedAfterHttpCallIsReceived() {
  console.log('3. Received too !', this.carListAfterManufacturerSelect); // filled
  // do a lot of complex stuff with carListAfterManufacturerSelect
}

订阅后服务价值仍未定义

Service values still undefined after subscribing

service

components

angular