groovy - Builder pattern with reactive programming -

i'm attempting use reactive programming (rxgroovy) create objects using builder pattern, property values come database queries. i'm looking first of all, how it, , second of all, thoughts on whether or not idea.

the objects i'm trying create of type:

class foo {     final string name;     final long[] relatedids;      foo(string name, long[] relatedids) {         this.name = name;         this.relatedids = relatedids;     } } 

and builder:

class foobuilder {     string name;     linkedlist<long> relatedids;      {         relatedids = new linkedlist<>();     }      foobuilder name(string name) {         this.name = name;         return this;     }      foobuilder relatedid(long id) {         this.relatedids.add(id);         return this;     }      foo build() {         return new foo(this.name, this.relatedids.toarray());     }  } 

i have 2 queries, 1 returns names of foo objects, , separate query run once each foo object related ids.

i have method (call queryasobservable) query , observable emits each row of result set. setting name this:

observable<foobuilder> buidlerswithnameset = queryasobservable(queryallfoos) .map { return new foobuilder().name(it.name); } 

and given foobuilder, set relatedids this:

final foobuilder builder; queryasobservable(queryrelatedids, builder.name)     .subscribe { builder.relatedid(it.id); } 

my problem how tie 2 together? how create observable set related ids, shown, each foobuilder emitted first observable? in end, need of foobuilder objects, name , relatedids properties set.

note joins

i know can related ids , name in 1 query join. thought can use lots of smaller queries running in parallel , uses observable streams work each result result becomes available, instead of waiting results come in , building objects serially. i'm open ideas on why that's or bad idea.

to combine observables use flatmap(). not sure of groovy syntax i'll take shot. starting builderwithnameset:

observable<foobuilder> completebuilder =     builderswithnameset         .flatmap { builder ->             return queryasobservable(queryrelatedids, builder.name)                 .map { builder.relatedid(it.id); }         }