Angular - 正确使用 RXJS 扩展运算符进行递归 http 调用
Angular - Correctly using RXJS expand operator to make recursive http calls
我正在尝试使用上一次调用的值对 Reddit 的 API 进行递归 http 调用。问题是上一个调用在下一个调用开始之前没有完成,所以重复调用。每次调用都应更新 "after" 值,直到 "after" 值未定义。我发现了这个 并尝试使用所描述的解决方案,但我无法弄清楚如何确保在进行下一次调用之前完成上一次调用。下面是我的实际代码:
private getSavedPostsForAuthenticatedUser(username: string, after: string, userPosts: any) {
const headers = new Headers();
if (!userPosts) {
userPosts = [];
}
headers.append('Authorization', `Bearer ${this._token}`);
const redditUrl = `${RetainerConfig.redditOauthUrl}user/${username}/saved`;
const url = after ? `${redditUrl}/?after=${after}` : redditUrl;
return this._http.get(url, { headers: headers })
.map(response => response.json())
.expand(response => {
if (response.data) {
for (const post of response.data.children) {
userPosts.push(post);
}
if (response.data.after) {
return this.getSavedPostsForAuthenticatedUser(username, response.data.after, userPosts);
}
}
return Observable.of(userPosts);
});
返回相同的函数getSavedPostsForAuthenticatedUser
将导致递归展开。要解决这个问题,您需要分离 http observable。
private getSavedPostsForAuthenticatedUser(username: string, after: string, userPosts: any) {
const request$ = this._getRequest(username, after, userPosts);
if (!userPosts) {
userPosts = [];
}
return request$
.expand(response => {
if (response.data) {
for (const post of response.data.children) {
userPosts.push(post);
}
if (response.data.after) {
return this._getRequest(username, response.data.after, userPosts);
}
}
return Observable.of(userPosts);
});
}
private _getRequest(username: string, after: string) {
const headers = new Headers();
headers.append('Authorization', `Bearer ${this._token}`);
const redditUrl = `${RetainerConfig.redditOauthUrl}user/${username}/saved`;
const url = after ? `${redditUrl}/?after=${after}` : redditUrl;
return this._http.get(url, {headers: headers})
.map(response => response.json());
}
要停止扩展,您可以使用 Observable.empty()
。请参考这个.
我正在尝试使用上一次调用的值对 Reddit 的 API 进行递归 http 调用。问题是上一个调用在下一个调用开始之前没有完成,所以重复调用。每次调用都应更新 "after" 值,直到 "after" 值未定义。我发现了这个
private getSavedPostsForAuthenticatedUser(username: string, after: string, userPosts: any) {
const headers = new Headers();
if (!userPosts) {
userPosts = [];
}
headers.append('Authorization', `Bearer ${this._token}`);
const redditUrl = `${RetainerConfig.redditOauthUrl}user/${username}/saved`;
const url = after ? `${redditUrl}/?after=${after}` : redditUrl;
return this._http.get(url, { headers: headers })
.map(response => response.json())
.expand(response => {
if (response.data) {
for (const post of response.data.children) {
userPosts.push(post);
}
if (response.data.after) {
return this.getSavedPostsForAuthenticatedUser(username, response.data.after, userPosts);
}
}
return Observable.of(userPosts);
});
返回相同的函数getSavedPostsForAuthenticatedUser
将导致递归展开。要解决这个问题,您需要分离 http observable。
private getSavedPostsForAuthenticatedUser(username: string, after: string, userPosts: any) {
const request$ = this._getRequest(username, after, userPosts);
if (!userPosts) {
userPosts = [];
}
return request$
.expand(response => {
if (response.data) {
for (const post of response.data.children) {
userPosts.push(post);
}
if (response.data.after) {
return this._getRequest(username, response.data.after, userPosts);
}
}
return Observable.of(userPosts);
});
}
private _getRequest(username: string, after: string) {
const headers = new Headers();
headers.append('Authorization', `Bearer ${this._token}`);
const redditUrl = `${RetainerConfig.redditOauthUrl}user/${username}/saved`;
const url = after ? `${redditUrl}/?after=${after}` : redditUrl;
return this._http.get(url, {headers: headers})
.map(response => response.json());
}
要停止扩展,您可以使用 Observable.empty()
。请参考这个