Flatten/Chain multiple nested firebase Observables -


i'm trying use angularfire2. querying , works fine below.

i want combine all/most of observables one:

gettournamentwithrounds(key):observable<tournament> {      return this.af.database         .object(`/tournaments/${key}`)         .map(tourney => {              let t = tournament.fromjson(tourney);              this.af.database.list('players', {                 query: {                     orderbychild: 'tournament_key',                     equalto: key                 }             })             .map(player.fromjsonlist)             .subscribe(ps => { t.players = ps; });              this.af.database.list('rounds', {                 query: {                     orderbychild: 'tournament_key',                     equalto: key                 }             })             .map(round.fromjsonlist)             .subscribe(rs => { t.rounds= rs; })              return t;         })   }

i wondering if join observables , output single subscribe function.

i know when initial data has been loaded , perform additional computation in controller before outputting view.

also, how extended include matches each round?

my extension above code be:

...  this.af.database.list('rounds', {     query: {         orderbychild: 'tournament_key',         equalto: key     } }) .map(rounds => {     return rounds.map((round) => {          let r = round.fromjson(round);          this.af.database.list('matches', {             query: {                 orderbychild: 'round_key',                 equalto: round.$key             }         })         .map(match.fromjsonlist)         .subscribe(matches => { r.matches = matches; })          return r;     }) }) .subscribe(rs => { t.rounds= rs; })  ...

you use combinelatest operator combine players , rounds tournament:

gettournamentwithrounds(key): observable<tournament> {    return this.af.database     .object(`/tournaments/${key}`)     .combinelatest(       this.af.database.list('players', {         query: {           orderbychild:'tournament_key',           equalto: key         }       }),       this.af.database.list('rounds', {         query: {           orderbychild:'tournament_key',           equalto: key         }       })     )     .map(([tourney, players, rounds]) => {        let t = tournament.fromjson(tourney);       t.players = player.fromjsonlist(players);       t.rounds = round.fromjsonlist(rounds);       return t;     }); }

whenever of observables emits, latest values re-combined , new tournament emitted.

extending include each round's matches little more complicated, each round's key needed matches query.

the emitted rounds can mapped array of list observables matches , forkjoin can used join observables, forkjoin selector function being used combine matches rounds. switchmap used emit rounds.

gettournamentwithrounds(key): observable<tournament> {    return this.af.database     .object(`/tournaments/${key}`)     .combinelatest(       this.af.database.list('players', {         query: {           orderbychild:'tournament_key',           equalto: key         }       }),       this.af.database.list('rounds', {         query: {           orderbychild:'tournament_key',           equalto: key         }       })       .switchmap(rounds => {         observable.forkjoin(           rounds.map(round => this.af.database.list('matches', {             query: {               orderbychild: 'round_key',               equalto: round.$key             }           }).first()),           (...lists) => rounds.map((round, index) => {             let r = round.fromjson(round);             r.matches = match.fromjsonlist(lists[index]);             return r;           })         )       })     )     .map(([tourney, players, rounds]) => {        let t = tournament.fromjson(tourney);       t.players = player.fromjsonlist(players);       t.rounds = rounds;       return t;     }); }

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