In my quest to develop a class that can retrieve/cache users from my Firestore database, I've encountered an issue where I'm unable to save or expose the previous promise that was generated. Below is the code snippet of my class:
export class UserCache {
private cacheTimeMilliseconds: number = 600000;
private userCache: any = {};
public getCacheUser(userid: string): Promise<User> {
return new Promise((resolve, reject) => {
let d = new Date();
d.setTime(d.getTime() - this.cacheTimeMilliseconds);
if (this.userCache[userid] && this.userCache[userid].complete && this.userCache[userid].lastAccess > d.getTime()) {
console.log("User cached");
resolve(this.userCache[userid].user);
}
console.log("Need to cache user");
this.userCache[userid] = {
complete: false
};
this.getSetUserFetchPromise(userid).then((data) => {
let user: User = <User>{ id: data.id, ...data.data() };
this.userCache[userid].user = user;
this.userCache[userid].complete = true;
this.userCache[userid].lastAccess = Date.now();
resolve(user);
});
});
}
private getSetUserFetchPromise(userid: string): Promise<any> {
console.log(this.userCache[userid]);
if (this.userCache[userid] && this.userCache[userid].promise) {
return this.userCache[userid].promise;
} else {
console.log("Creating new user fetch request.");
this.userCache[userid].promise = firestore().collection('users').doc(userid).get();
console.log(this.userCache[userid]);
return this.userCache[userid].promise;
}
}
}
The logs reveal that the promise is being set in getSetUserFetchPromise, but upon subsequent function calls, the property seems to be unset. This leads me to suspect it's either a scope or concurrency issue, which I'm struggling to address.
I invoke getCacheUser in a consuming class using let oCache = new UserCache() and oCache.getCacheUser('USERID')
Following Tuan's answer below
UserCacheProvider.ts
import firestore from '@react-native-firebase/firestore';
import { User } from '../static/models';
class UserCache {
private cacheTimeMilliseconds: number = 600000;
private userCache: any = {};
public getCacheUser(userid: string): Promise<User> {
return new Promise((resolve, reject) => {
let d = new Date();
d.setTime(d.getTime() - this.cacheTimeMilliseconds);
if (this.userCache[userid] && this.userCache[userid].complete && this.userCache[userid].lastAccess > d.getTime()) {
console.log("User cached");
resolve(this.userCache[userid].user);
}
console.log("Need to cache user");
this.userCache[userid] = {
complete: false
};
this.getSetUserFetchPromise(userid).then((data) => {
let user: User = <User>{ id: data.id, ...data.data() };
this.userCache[userid].user = user;
this.userCache[userid].complete = true;
this.userCache[userid].lastAccess = Date.now();
resolve(user);
});
});
}
private getSetUserFetchPromise(userid: string): Promise<any> {
console.log(this.userCache[userid]);
if (this.userCache[userid] && this.userCache[userid].promise) {
return this.userCache[userid].promise;
} else {
console.log("Creating new user fetch request.");
this.userCache[userid].promise = firestore().collection('users').doc(userid).get();
console.log(this.userCache[userid]);
return this.userCache[userid].promise;
}
}
}
const userCache = new UserCache();
export default userCache;
ChatProvider.ts (usage)
let promises = [];
docs.forEach(doc => {
let message: Message = <Message>{ id: doc.id, ...doc.data() };
promises.push(UserCacheProvider.getCacheUser(message.senderid).then((oUser) => {
let conv: GCMessage = {
_id: message.id,
text: message.messagecontent,
createdAt: new Date(message.messagedate),
user: <GCUser>{ _id: oUser.id, avatar: oUser.thumbnail, name: oUser.displayname }
}
if (message.type && message.type == 'info') {
conv.system = true;
}
if (message.messageattachment && message.messageattachment != '') {
conv.image = message.messageattachment;
}
return conv;
}));
});
Promise.all(promises).then((values) => {
resolve(values);
});