问题
I have an Angular2 (ionic2) application. I have a function that request cities but I get an error that Property subscribe does not exists on this.cityService.getAllCities().
cityPage.ts has a function like this:
getCities(){
this.cityService.getAllCities()
.subscribe(cityData => { this.cityList = cityData; },
err => console.log(err),
() => console.log('Complete!')
);
}
my cityService.getAllCities() function looks like this:
getAllCities(){
return new Promise (resolve => {
this.storage.ready().then(() => {
this.storage.get('authData').then(authData => {
let hdr = new Headers({'Content-Type': 'application/json', 'Authorization': 'Bearer ' +
authData.access_token });
let opt = new RequestOptions({ headers: hdr });
return this.http.get(AppSettings.API_GET_CITIES).map(res => <CityModel[]> res.json(), opt);
}).catch(() => {
//resolve(false);
});
});
});
}
Edit
Based on the comment I've changed my function like this:
getAllCities(){
return Observable.create(resolve => {
this.storage.ready().then(() => {
this.storage.get('authData').then(authData => {
let hdr = new Headers({'Content-Type': 'application/json', 'Authorization': 'Bearer ' +
authData.access_token });
console.log('access_token ' + authData.access_token);
let opt = new RequestOptions({ headers: hdr });
return this.http.get(AppSettings.API_GET_CITIES,opt).map(res => <CityModel[]> res.json()).subscribe((result) => {
console.log(result);
resolve = result;
});
}).catch(() => {
//resolve(false);
});
});
});
}
In my console.log(result) I receive data, but the data is never returned to my getCities() function. Also the console.log('Complete!') is not called.
回答1:
The reason it is throwing an error, because .subscribe method does available on Observable to listen to, whenever it emits a data. Here from getAllCities method you're returning a promise you could apply .then function over it to get data returned from that Promise
getCities() {
this.cityService.getAllCities()
.then(
cityData => { this.cityList = cityData; },
err => console.log(err),
() => console.log('Complete!')
);
}
And also return promise from getAllCities method by calling .toPromise() method over http.get() Observable.
getAllCities(){
return new Promise (resolve => {
this.storage.ready().then(() => {
this.storage.get('authData').then(authData => {
let hdr = new Headers({'Content-Type': 'application/json', 'Authorization': 'Bearer ' +
authData.access_token });
let opt = new RequestOptions({ headers: hdr });
//returned promise from here.
return this.http.get(AppSettings.API_GET_CITIES)
.map(res => <CityModel[]> res.json(), opt)
.toPromise();
}).catch(() => {
//resolve(false);
});
});
});
}
来源：https://stackoverflow.com/questions/43596530/promise-and-subscribe