Flutter future.then() returns empty string

Question

The following code print the right string.

String genreString = '';
for (var genreID in list["genre_ids"]) {
     DBProvider.db.getGenreName(genreID).then((value) {
          genreString = genreString + value + ", ";
          print(genreString);
     });
}

But I want to acess "genreString" outside the for loop. When I want to print it like this.

String genreString = '';
for (var genreID in list["genre_ids"]) {
     DBProvider.db.getGenreName(genreID).then((value) {
          genreString = genreString + value + ", ";
     });
}
print(genreString);

it would not work. I also try "return" but it does not change.

May someone have a solution

final genreNames = await Future.wait(list["genre_ids"].map(DBProvider.db.getGenreName)) — pskink
– pskink, Commented Jan 8, 2021 at 12:06

dshukertjr · Accepted Answer · 2021-01-07 23:12:13Z

2

This should work. Note that the function containing this code has to be async.

String genreString = '';
for (var genreID in list["genre_ids"]) {
     final value = await DBProvider.db.getGenreName(genreID);
     genreString = genreString + value + ", ";
}
print(genreString);

answered Jan 7, 2021 at 23:12

dshukertjr

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