Created
November 22, 2016 13:44
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RxJS MongoDB Query Builder
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/* @flow */ | |
import { Observable, Disposable, ReplaySubject } from 'rx'; | |
import mongo from 'mongodb'; | |
import { dbUrl } from './config'; | |
import { assign } from 'lodash'; | |
class QueryBuilder { | |
_db$: Observable; | |
_selectors: Object; | |
_sub: Disposable; | |
constructor(db$: Observable, selectors?: Object) { | |
this._db$ = db$; | |
if (!selectors) { | |
this._selectors = assign({ | |
collection: null, | |
query: {}, | |
opts: {}, | |
sort: {}, | |
offset: 0, | |
limit: 0 | |
}, selectors); | |
} | |
else { | |
this._selectors = selectors; | |
} | |
} | |
static connect(url: string): QueryBuilder { | |
var db$ = new ReplaySubject(1); | |
mongo.connect(url, (err, db) => { | |
if (err) { | |
db$.onError(err); | |
} | |
else { | |
db$.onNext(db); | |
} | |
db$.onCompleted(); | |
}); | |
this._sub = db$.subscribe( | |
_ => console.log('Connected to database on', url), | |
err => console.error('Database connection error:', err.message, err.stack) | |
); | |
return new QueryBuilder(db$); | |
} | |
close(): any { | |
this._sub.dispose(); | |
return QueryBuilder; | |
} | |
collection(name: string): QueryBuilder { | |
const ss = assign({}, this._selectors, { collection: name }); | |
return new QueryBuilder(this._db$, ss); | |
} | |
select(query?: Object = {}, opts?: Object = {}): QueryBuilder { | |
const ss = assign({}, this._selectors, { query, opts }); | |
return new QueryBuilder(this._db$, ss); | |
} | |
selectOne(query?: Object = {}, opts?: Object = {}): QueryBuilder { | |
const ss = assign({}, this._selectors, { | |
query: query, | |
opts: opts, | |
limit: 1 | |
}); | |
return new QueryBuilder(this._db$, ss); | |
} | |
sort(sort: Object): QueryBuilder { | |
const ss = assign({}, this._selectors, { sort }); | |
return new QueryBuilder(this._db$, ss); | |
} | |
skip(offset: number): QueryBuilder { | |
const ss = assign({}, this._selectors, { offset }); | |
return new QueryBuilder(this._db$, ss); | |
} | |
limit(limit: number = 0): QueryBuilder { | |
const ss = assign({}, this._selectors, { limit }); | |
return new QueryBuilder(this._db$, ss); | |
} | |
exec(): Observable { | |
const ss = this._selectors; | |
let db$ = this._db$ | |
if (!ss.collection) return Observable.throw('You have to provide collection name.'); | |
if (!db$) return Observable.throw('No db connection found.'); | |
let o = db$ | |
.flatMapLatest(db => { | |
var c = db.collection(ss.collection); | |
var cursor = c.find(ss.query, ss.opts).sort(ss.sort).skip(ss.offset).limit(ss.limit); | |
var obs = Observable.fromNodeCallback(cursor.toArray, cursor); | |
return obs(); | |
}) | |
.finally(() => { | |
this._$db = null; | |
this._selectors = null; | |
}); | |
return ss.limit === 1 ? o.map(res => res[0]) : o; | |
} | |
} | |
export default QueryBuilder.connect(dbUrl); |
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