CODEWITHSUNDEEP
flutterloopsdart
QQew
QQew

Reputation: 83

How can I find the number of objects in a list defined with a certain field? Flutter

So I need to count the number of objects in the List that have a field with the value "Category.walking". I tried iterating over with both "for" loop and "forEach".

int countPets(){
int count = 0;
  pets.forEach((element) {
    if (pets.contains(category.walking)){
      count++;
    }
  }
);
  return count;

}

But there is only one mistake - "Undefined name 'category'. Try correcting the name to one that is defined, or defining the name." or The name 'Category' is defined in the libraries 'package:flutter/src/foundation/annotations.dart (via package:flutter/foundation.dart)' and 'package:petts/data.dart'. Try using 'as prefix' for one of the import directives, or hiding the name from all but one of the imports.

This is how i made the data set in data.dart----

enum Category { walking, grooming, doctor, shop }
enum Condition { park, cafe, training }

class Pet {
  String name;
  String location;
  String distance;
  String condition;
  Category category;
  String imageUrl;
  bool favorite;
  bool newest;

  Pet(this.name, this.location, this.distance, this.condition, this.category,
      this.imageUrl, this.favorite, this.newest);
}

List<Pet> getPetList() {
  return <Pet>[
    Pet(
      "",
      "",
      "",
      "",
      Category.walking,
      "",
      true,
      true,
    ),
    Pet(
      "",
      "",
      "",
      "",
      Category.walking,
      "",
      false,
      false,
    ),
    Pet(
      "",
      "",
      "",
      "",
      Category.grooming,
      "",
      true,
      true,
    ),
  ];
}

And this in how i use this getPetList() in home_page.dart----

class HomePage extends StatefulWidget {
  const HomePage({Key? key}) : super(key: key);

  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  List<Pet> pets = getPetList();

   ...there i need a counter...

Please, help me

Upvotes: 0

Views: 1674

Answers (3)

Arbiter Chil
Arbiter Chil

Reputation: 1255

try using where then length

       final count = getPetList().where((e)=>
 e.category.name == Category.walking.name ).length;

  print(count);
    
      //result 2

Upvotes: 0

Prateek Jain
Prateek Jain

Reputation: 604

Try this code.... Pass your list as a parameter to this method and it will return the desired count.

int countPets(List<Pet> pets) {
      int count = 0;
      pets.forEach((element) {
        if (element.category == Category.walking) {
          count++;
        }
      });
      return count;
    }

Upvotes: 0

Aron
Aron

Reputation: 92

Try this:

for (var element in pets) {
  if (element.category == Category.walking){
    count++;
  }
}

Upvotes: 1

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