Flutter - creating a search delegate data 'getter' model, from CSV data - json

Question

At the moment, I am building a Flutter app to try and develop my skills, which includes a search delegate function. At the moment, my search delegate works great, when the data is imported from json format, which looks like this:
[
{
name: John,
age: 22,
height: 1.85,
searchTerm: John 22 1.85,
},
{
name: Alice,
age: 24,
height: 1.90,
searchTerm: Alice 24 1.90,
},
{
name: Bruce,
age: 35,
height: 1.76,
searchTerm: Bruce 35 1.76,
}
]
To allow my search delegate to work, I built a getter model that looks like this.
import 'dart:convert';
import 'package:flutter/services.dart';
class People {
final String name;
final double age;
final double height;
final String searchTerm;
People({
required this.name,
required this.age,
required this.height,
required this.searchTerm,
});
static People fromJson(Map<String, dynamic> json) => People(
name: json['name'],
age: json['age'],
height: json['height'],
searchTerm: json['searchTerm'],
);
}
class PeopleGetter {
static Future<List<People>> getPeopleSuggestions(String query) async {
try {
final String response =
await rootBundle.loadString('assets/data/people.json');
final List people = json.decode(response);
return people
.map((json) => People.fromJson(json))
.where((people) {
final searchTermLower = people.searchTerm.toLowerCase();
final queryLower = query.toLowerCase();
return searchTermLower.contains(queryLower);
}).toList();
} catch (e) {
print(e);
}
throw '';
}
}
This actually does work perfectly with my search delegate. However, since storing the data in a CSV file can significantly reduce the overall data size, and therefore the overall app size, I want to replace the json data with CSV data. I've tried modifying my 'getter' function from json data, to use CSV data (using the CSV package, from pub.dev), which you can see here:
import 'package:csv/csv.dart';
import 'package:flutter/services.dart';
class People {
final String name;
final double age;
final double height;
final String searchTerm;
People({
required this.name,
required this.age,
required this.height,
required this.searchTerm,
});
static People fromCSV(Map<String, dynamic> csv) => People(
name: csv['name'],
age: csv['age'],
height: csv['height'],
searchTerm: csv['searchTerm'],
);
}
class PeopleGetter {
static Future<List<People>> getPeopleSuggestions(String query) async {
try {
final String response =
await rootBundle.loadString('assets/data/people.csv');
final List people = CsvToListConverter(response);
return people
.map((csv) => People.fromCSV(csv))
.where((people) {
final searchTermLower = people.searchTerm.toLowerCase();
final queryLower = query.toLowerCase();
return searchTermLower.contains(queryLower);
}).toList();
} catch (e) {
print(e);
}
throw '';
}
}
Unfortunately, when I use this version within the search delegate, I get the error:
'type 'List<dynamic>' is not a subtype of type 'Map<String, dynamic>'.
I feel like I'll just have made a very simple error somewhere but at the moment, I just can't spot it. I would really appreciate any help correcting my code, to allow me to search with CSV data, instead of JSON data. Thanks!

Answer 1

It seems that your data types are not corresponding anymore:
You provide a List<dynamic> to a function that expects a Map<>
people.map((csv) => People.fromCSV(csv))
static People fromCSV(Map<String, dynamic> csv) => People(
name: csv['name'],
age: csv['age'],
height: csv['height'],
searchTerm: csv['searchTerm'],
);
Could you try rewriting your function from CSV to adapt to the new incoming data ? I'm not sure what is the data you get but maybe something like that ?
static People fromCSV(List<dynamic> csv) => People(
name: csv[0] ?? "",
age: csv[1] ?? -1,
height: csv[2] ?? -1,
searchTerm: csv[3] ?? "",
);
EDIT (fixing the few remaining bugs)
Updated CSV package version
Correctly retrieve the double from the csv
Set the delimiter parameter to separate two people in the CSV
class People {
final String name;
final double age;
final double height;
final String searchTerm;
People({
required this.name,
required this.age,
required this.height,
required this.searchTerm,
});
static People fromCSV(List<dynamic> csv) => People(
name: csv[0] ?? '',
age: double.parse(csv[1].toString()),
height: double.parse(csv[2].toString()),
searchTerm: csv[3] ?? '',
);
}
class PeopleGetter {
static Future<List<People>> getPeopleSuggestions(String query) async {
try {
final String response = await rootBundle.loadString('assets/data.csv');
final List<List<dynamic>> people =
CsvToListConverter().convert(response, eol: "\n");
return people.map((csv) => People.fromCSV(csv)).where((people) {
final searchTermLower = people.searchTerm.toLowerCase();
final queryLower = query.toLowerCase();
return searchTermLower.contains(queryLower);
}).toList();
} catch (e) {
print(e);
}
throw '';
}
}