我的 Typescript 中有以下方法!
allPowerPlants(onlyActive: boolean = false, page: number = 1): PowerPlant[] {
const params: string = [
`onlyActive=${onlyActive}`,
`page=${page}`
].join('&');
const path = `${this.allPowerPlantsURL}?${params}`;
this.apiService.get(path).map(
powerplants => {
powerplants.map(item => {
if (this.isPowerPlant(item)) {
// make the item an instance of PowerPlant
this.powerPlants.push(item as PowerPlant);
}
});
},
err => {
console.log('oops **** some error happened');
// handle error
});
console.log('powerplants obtained is *****************+ ');
console.log(this.powerPlants);
return this.powerPlants;
}
我的获取方法如下所示:
import { Injectable } from '@angular/core';
import { environment } from '../../environments/environment';
import { Headers, Http, Response, URLSearchParams } from '@angular/http';
import { Observable } from 'rxjs/Rx';
import 'rxjs/add/operator/map';
import 'rxjs/add/operator/catch';
@Injectable()
export class ApiService {
loading: boolean;
data: Object;
constructor(
private http: Http,
) {}
get(path: string, params: URLSearchParams = new URLSearchParams()): Observable<any> {
console.log('sending request to ' + `${environment.api_url}${path}`);
return this.http.get(`${environment.api_url}${path}`, { search: params })
.catch(this.formatErrors)
.map((res: Response) => {
console.log('response as json is ' + res.json());
res.json();
});
}
}
我的 isPowerPlant 方法如下所示:
isPowerPlant(item: any): item is PowerPlant {
// check for the required properties of PowerPlant here and return true/false.
// example:
console.log('in the static method');
const vvvv = item['maxPower'] && item['minPower'];
console.log(vvvv);
return vvvv;
}
我期待在 console.log('response as json is ') 中看到一些数据,但奇怪的是它什么也没打印!请求甚至没有发送到服务器!
但是,当我将 allPowerPlants 方法更改为不映射 get 方法,而是像下面那样订阅时:
this.apiService.get(path).subscribe(...)
我可以看到正在从服务器获取一些数据,正如我从我的服务器日志中看到的那样,请求正在得到处理。
我想做以下事情:
我希望 allPowerPlants 返回一个 PowerPlants 数组,其定义如下:
export interface PowerPlant {
powerPlantId: number;
powerPlantName: string;
minPower: number;
maxPower: number;
powerPlantType: string;
rampRateInSeconds?: number;
rampPowerRate?: number;
}
现在因为我的 get 方法是一个 Observable,我看到我的 Angular 应用程序正在对服务器进行大量调用,这可以从我的服务器日志中看到:
[info] application - GET /powerPlants?onlyActive=false&page=1 took 3192ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2974ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2701ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2682ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2885ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2920ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2552ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2564ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2598ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2612ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2615ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2621ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2636ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2609ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2701ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2544ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2588ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2532ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2586ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2570ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2652ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2624ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2661ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2618ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2611ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2624ms HTTP status >> 200
[info] application - GET /powerPlants?onlyActive=false&page=1 took 2620ms HTTP status >> 200
这是我的服务器发送的实际数据:
[ {
"powerPlantId" : 1,
"powerPlantName" : "Organization-001",
"minPower" : 20,
"maxPower" : 100,
"powerPlantType" : "OnOffType"
}, {
"powerPlantId" : 2,
"powerPlantName" : "Organization-001",
"minPower" : 100,
"maxPower" : 800,
"rampPowerRate" : 100,
"rampRateInSeconds" : 100,
"powerPlantType" : "RampUpType"
}, {
"powerPlantId" : 3,
"powerPlantName" : "Organization-002",
"minPower" : 200,
"maxPower" : 400,
"rampPowerRate" : 50,
"rampRateInSeconds" : 50,
"powerPlantType" : "RampUpType"
}, {
"powerPlantId" : 4,
"powerPlantName" : "Organization-002",
"minPower" : 400,
"maxPower" : 800,
"powerPlantType" : "OnOffType"
} ]
如何让我的 allPowerPlants 只调用我的服务器一次,但同时处理来自 get 方法的 Observable 结果?
这就是我在 HTML 中使用数据的方式:
<div class="ui grid posts">
<app-powerplant
*ngFor="let powerPlant of allPowerPlants()"
[powerPlant]="powerPlant">
</app-powerplant>
</div>
最佳答案
这是从服务器调用数据的代码片段
this.apiService.get(path).map(
powerplants => {
...
}
停在那里。没有数据是因为你没有订阅! 你应该这样做
this.apiService.get(path).subscribe(
powerplants => {
this.powerPlants = powerplants
//remove the mapping. you can do it in your service.
},
err => {
console.log('oops **** some error happened');
// handle error
});
为您服务
get(path: string, params: URLSearchParams = new URLSearchParams()): Observable<any> {
console.log('sending request to ' + `${environment.api_url}${path}`);
return this.http.get(`${environment.api_url}${path}`, { search: params })
.catch(this.formatErrors)
.map((res: Response) => {
<PowerPlant[]> res.json();
});
}
请注意,我的映射可能是错误的,因为您没有显示返回数据的实际值。
希望这对您有所帮助。
关于json - Angular 4 HTTP 不返回 JSON 正文,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/45958470/