I have a list of objects (City) that contains a lot of properties it's internal structure:
class City {
String id;
String name;
String parent_id;
double lat;
double lng;
String local;
}
how to get a list of names(Strings) from the same list of cities
List<City> cities
how to get List<String> names from cities
For example:
class City {
const City(this.id, this.name);
final int id;
final String name;
}
List<City> cities = [
City(0, 'A'),
City(1, 'B'),
City(2, 'C'),
];
final List<String> cityNames = cities.map((city) => city.name).toList();
void main() {
print(cityNames);
}
It's simple and cumbersome though,
var cityNames = cities.map((c) => c.name).toList().join(',');
Use this
List<String> cityNameList = cities.map((city) => city.name).toList();
You can also go through explanation below
CustomData Class
class City {
String id;
String name;
String parent_id;
double lat;
double lng;
String local;
}
Map List<City> to List<String> based on any member of City class
List<City> cities= getListOfCities();
// city.name, city.local...any field as you wish
List<String> cityNameList = cities.map((city) => city.name).toList();
print(cityNameList);
An alternative, if you want to extract a list of string from list of object, with selected or enabled flag.
To do that, you can remove objects with selected=false or something like name.length > 5, then do map.tolist to extract the list of string.
Usually i use this method to get filters to filtering search result. Example we have a products list with distance & country filters. We can simply use solution above and apply filter with selected true.
I don't speak english, hope you understand 😅.
class City {
const City(this.name, [this.selected= false]);
final String name;
final bool selected;
}
void main() {
final cities = [City('A'), City('B', true), City('C')];
cities.add(City('D', true));
/// Remove unselected items
cities.removeWhere((e) => !e.selected);
/// extract list of string from list of objects
final selectedCities = cities.map((c) => c.name).toList();
print(selectedCities);
}
print:
[B, D]
List<String> names=[];
for (City city in cities){
names.add(city.name);
}
