How can I output my object properties with this enumerating extension in Flutter/Dart?

Question

I want to print specific individualized object properties with this extension- Source: HERE

extension ExtendedIterable<E> on Iterable<E> {
  /// Like Iterable<T>.map but callback have index as second argument
  Iterable<T> mapIndex<T>(T f(E e, int i)) {
    var i = 0;
    return this.map((e) => f(e, i++));
  }

  void forEachIndex(void f(E e, int i)) {
    var i = 0;
    this.forEach((e) => f(e, i++));
  }
}

I am saving user data from textFields into a Hive box.

When I do the following...

final box = Hive.box(personTable).values.toList();
    final hiveBox = Hive.box(personTable);
    final indexingBox = box.mapIndex((e, i) => 'item$e index$i');
    final Person person = hiveBox.getAt(0);
    print(person);
    print(indexingBox);

I get the following printed:

flutter: {John, Biggs, 34, Active}
flutter: (item{John, Biggs, 34, Active} index0, item{Kostas, Panger, 76, Active} index1, item{Ben, Kenobi, 78, Deactivated} index2, ..., item{Luke, Skywalker, 45, Active} index5, item{Darth, Vader, 54, Active} index6)

I want to be able to enumerate selectively, each object property as I please.

This is what I want to be able to print:

• flutter: John. // index 0 firstName
• flutter: Kostas // index 1 firstName
• flutter: Vader // index 6 lastname

Class saving into Hive box:

import 'package:hive/hive.dart';
part 'person.g.dart';

@HiveType(typeId: 0)
class Person {
  @HiveField(0)
  final String firstName;
  @HiveField(1)
  final String lastName;
  @HiveField(2)
  final String age;
  @HiveField(3)
  final String status;
  Income({
    this.firstName,
    this.lastName,
    this.age,
    this.status,
  });
  @override
  String toString() {
    return '{${this.firstName}, ${this.lastName}, ${this.age}, ${this.status}}';
  }
}

If I can't solve this once and for all my head may as well explode, this is part of a bigger picture of making a DataTable very simple and dynamically loading. Help is appreciated!

Solution 1

SOLVED, FINALLY!!!

box.forEachIndex((e, i) {
      final hiveBox = Hive.box(personTable);
      final person = hiveBox.getAt(i) as Person;
      print('${person.firstName}');
    });

Console

flutter: John
flutter: Obi-wan
flutter: Luke

Solution 2

From your list, you can just get the firstName and pass it in the function :

If you use a model :

class Person {
  final String firstName;
  final String lastName;
  final String age;
  final String status;

  Person(
    this.firstName,
    this.lastName,
    this.age,
    this.status,
  );
  @override
  String toString() {
    return '{${this.firstName}, ${this.lastName}, ${this.age}, ${this.status}}';
  }

  factory Person.fromJson(List<String> list) {
    return Person(list[0], list[1], list[2], list[3]);
  }
}
    
    
void main() {

List<String> listPerson = <String>[];
  
  final box = Hive.box(personTable).values.toList();
  
  box.forEach((element) { final test = element.toString(); listPerson.add(test); print(test); });

List<String> listPersonWithoutBracket = <String>[];

  for (var i = 0; i < listPerson.length; i++) {
    String strWithoutBracket =
        listPerson[i].replaceAll("{", "").replaceAll("}", "").trim();

    listPersonWithoutBracket.add(strWithoutBracket);
  }

  List<List<String>> listPersonResult = <List<String>>[];

  for (var i = 0; i < listPersonWithoutBracket.length; i++) {
    var strSplit = listPersonWithoutBracket[i].split(", ");
    listPersonResult.add(strSplit);
  }
  
  List<Person> listPersonFinal = listPersonResult.map((item) => Person.fromJson(item)).toList();
  
  final allFirstName = listPersonFinal.map((item) {
          return item.firstName;
      });
  
  final indexingBox = allFirstName.mapIndex((e, i) => '$e');
      print(indexingBox);
        
    }

Outputs

 John, Kostas

Comments

[RobbB]

Tried this and I get an error: The following NoSuchMethodError was thrown building PersonPage(dirty): Class 'Person' has no instance method '[]'. Receiver: Instance of 'Person' Tried calling: [](0)

[RobbB]

Sorry I somehow missed the top half of you're post. Will try that now!

[Lapa Ny Aina Tanjona]

You have named your class in your constructor Income instead of Person! Person({ this.firstName, this.lastName, this.age, this.status, });

[RobbB]

I posted that error from a second section of my project where I tried it, I updated it with the Person section error

[Lapa Ny Aina Tanjona]

Can you output the box variable ?

[RobbB]

The box variable prints like so: `flutter: (item{John, Biggs, 34, Active} index0, item{Kostas, Panger, 76, Active} index1, item{Ben, Kenobi, 78, Deactivated} index2, ..., item{Luke, Skywalker, 45, Active} index5, item{Darth, Vader, 54, Active} index6). Anyway trying this again

[RobbB]

Okay tried it and I get this error: type 'Person' is not a subtype of type 'Map<String, dynamic>' which I do not understand

[Lapa Ny Aina Tanjona]

Yes! This error appears because the type of the variable in my example is not the same with the type of the variable in hivebox! Can you tell me what is the type of the box variable? String or List? And can you output the hiveBox variable too? Thanks. I've never work with Hive before but if I know the correct variable, we resolve your question.

[RobbB]

Absolutely, the box is List<dynamic> and the hiveBox is Box<dynamic>

[RobbB]

So far I have gotten closer using forEach() like so: box.forEach((element) { final test = element.toString(); print(test); }); this prints enumerations for each object stored in the box Example: flutter: {John, Biggs, 34, Active} flutter: {Kostas, Panger, 76, Active}

[Lapa Ny Aina Tanjona]

Okay! I can take your solution from there. I was creating an app and really testing locally with the hive package.

[RobbB]

Unfortunately the change gave me the exact same results as the forEach example. Prints each object individually but cannot access each object property. This is crazy! I feel like this is a Hive problem or hive complexity and Hive documentation isn't thorough enough for performing actions like this.

[Lapa Ny Aina Tanjona]

Yes, but with my example you can get the List<Person> with a Person Model : ( List<Person> listPersonFinal )

[RobbB]

I didn’t notice that, I will give it another shot a little later today. Thanks for the help so far!