我對nodejs/typescript/promises比較陌生,所以我不確定鏈接promise的正確方法。你如何鏈接承諾,但從一個到另一個改變類型?
我有一個幫助類,它調用REST api來獲取基於ip的地理位置。我對整個迴應不感興趣,只有城市領域。我如何正確地返回一個承諾,解決只有獲得城市領域?
var rest = require("axios");
const ENDPOINT = "http://freegeoip.net/json/";
@Service()
export class GeoIp {
city(ip: string): Promise<any> {
let promise: Promise<any>;
let p = rest.get(ENDPOINT + ip);
p.then((response) => {
promise = Promise.resolve(() => {return response.data["city"]});
}, (error) => {
promise = Promise.reject(() => { return error});
});
return Promise.resolve(p).then((data)=>promise);
}
}
這是我的測試代碼失敗,因爲接收到的數據對象是原始REST響應對象
import chai = require('chai');
import {GeoIp} from "../../server/services/GeoIp";
var assert = chai.assert;
describe("GeoIp service",() => {
let geoIp: GeoIp;
beforeEach("Initialize service",() => {
geoIp = new GeoIp();
});
var IP_VALID = "137.118.222.187";
it(`Check geolocation of ${IP_VALID}`, (done) => {
let promise = geoIp.city(IP_VALID);
promise.then((data) => {
console.log(data);
assert.equal(data, "Traphill");
done();
});
});
});
如答案中所示,沒有必要創建自己的承諾。事實上,這樣做是[反模式](https://github.com/petkaantonov/bluebird/wiki/Promise-anti-patterns#the-deferred-anti-pattern) – cartant