Asynchronous building a array, iterating of other arrays

Question

I try to build a keyword list from all existing keywords. I manage to retrieve them all and output them in the debug console.

I am confused about how and when to call resolve(taxonomyKeywords). I like to call it when all loops and their inner loops are finished. I tried using foreach, yet run in the same issue. Is my approach way off and there's a much easier way?

private searchKeyword(searchTerm: string, results: ITag[]) : ITag[] | Promise<ITag[]>
{
  return new Promise<IPersonaProps[]>( (resolve, reject) => {
    let taxonomyKeywords : ITag[] = [];

    this.props.taxonomyProvider.getTermStores().then( (stores: ITermStore[]) => {
      for(var store of stores )
      {
        this.props.taxonomyProvider.getTermGroups( store.id ).then( (groups: ITermGroup[]) => {

          for(var group of groups)
          {
            this.props.taxonomyProvider.getTermSets(group).then( (sets: ITermSet[]) => {
              for(var termSet of sets)
              {
                this.props.taxonomyProvider.getTerms(termSet).then( (terms: ITerm[]) => {
                  for(var term of terms)
                  {
                    if( term.name.indexOf(searchTerm) >= 0 )
                    {
                      taxonomyKeywords.push( { key: term.name, name: term.name} );
}}});}});}});}});});}

You never should call resolve, as you should avoid the Promise constructor antipattern! — Bergi
– Bergi, Commented Jul 11, 2017 at 6:02

Howard · Accepted Answer · 2017-07-11 06:59:42Z

1

I think below pattern shall be better:

private function searchKeyword(searchTerm: string, results: ITag[]): ITag[] | Promise<ITag[]> {

    return this.props.taxonomyProvider
        .getTermStores()
        .then((stores: ITermStore[]) => {
            return Promise.all(stores.map(s => this.props.taxonomyProvider.getTermGroups(s.id)));
        })
        .then((groups: Array<ITermGroup[]>) => {

            const flattenGroups: ITermGroup[] = groups.reduce((p, c) => p.concat(c), []);

            return Promise.all(flattenGroups.map(g => this.props.taxonomyProvider.getTermSets(g)));
        })
        .then((sets: Array<ITermSet[]>) => {
            const flattenSets: ITermSet[] = sets.reduce((p, c) => p.concat(c), []);

            return Promise.all(flattenSets.map(s => this.props.taxonomyProvider.getTerms(s)));
        })
        .then((terms: Array<ITerm[]) => {
            const flattenTerms: ITerm[] = terms.reduce((p, c) => p.concat(c), []);
            return flattenTerms
                .filter(t => t.name.indexOf(searchTerm) >= 0)
                .map(t => ({ key: t.name, name: t.name }));
        });
}

You should learn how promise work

edited Jul 11, 2017 at 6:59

answered Jul 11, 2017 at 6:11

Howard

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4 Comments

Dennis Kuhn Over a year ago

Re: "learn how promise work" - I am trying to :-) It's more the mapping thing. I give your pattern a go ... Thanks a lot already :-)

Bergi Over a year ago

This doesn't work. Those taxonomyProvider.getXY methods all return promises, and you cannot just return an array of promises from then

Dennis Kuhn Over a year ago

I think that is the error I am getting now:

Error - typescript - : error TS2345: Argument of type '(groups: ITermGroup[][]) => Promise<ITermSet[]>[]' is not assignable  to parameter of type '(value: Promise<ITermGroup[]>[]) => Promise<ITermSet[]>[] | PromiseLike<Promise<ITermSet[]>[]>'.

Dennis Kuhn Over a year ago

Awesome thanks a lot that worked like a charm and I am learning :-)

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