dictionary - Flutter : Mapping two lists toegther

Dictionary - Flutter : Mapping two lists toegther

In Flutter, you can map two lists together using the List.generate function or the Iterable.zip method from the collection package. Here's how you can do it using both methods:

  1. Using List.generate:
List<String> keys = ['a', 'b', 'c']; List<int> values = [1, 2, 3]; Map<String, int> result = Map.fromIterables(keys, List.generate(keys.length, (index) => values[index])); print(result); // Output: {a: 1, b: 2, c: 3}
  1. Using Iterable.zip (from collection package):

First, ensure you have added the collection package to your pubspec.yaml file:

dependencies: flutter: sdk: flutter collection: ^1.15.0

Then, import the package and use Iterable.zip:

import 'package:collection/collection.dart'; List<String> keys = ['a', 'b', 'c']; List<int> values = [1, 2, 3]; Map<String, int> result = Map.fromIterables(keys, IterableZip([keys, values]).map((item) => item[1])); print(result); // Output: {a: 1, b: 2, c: 3}

Both approaches will produce a map where elements of the keys list are keys, and elements of the values list are values in the resulting map. Adjust the code according to the types of your lists and the specific mapping logic you need.

Examples

  1. Mapping Two Lists into a Dictionary in Flutter

    • Description: This snippet demonstrates how to combine two lists into a dictionary (Map) where one list represents keys and the other represents values.
    • Code:
      List<String> keys = ['name', 'age', 'city']; List<dynamic> values = ['Alice', 30, 'New York']; Map<String, dynamic> dictionary = Map.fromIterables(keys, values); print(dictionary); // Output: {name: Alice, age: 30, city: New York}

  2. Combining Two Lists into a Map with Dart

    • Description: This code snippet shows how to create a map by combining two lists using Dart's zip method.
    • Code:
      List<String> keys = ['id', 'title', 'price']; List<dynamic> values = [101, 'Book', 9.99]; Map<String, dynamic> map = Map.fromIterables(keys, values); print(map); // Output: {id: 101, title: Book, price: 9.99}

  3. Creating a List of Tuples from Two Lists in Flutter

    • Description: This query shows how to create a list of tuples by mapping two lists together.
    • Code:
      List<String> list1 = ['a', 'b', 'c']; List<int> list2 = [1, 2, 3]; List<Tuple> tuples = []; for (var i = 0; i < list1.length; i++) { tuples.add(Tuple(list1[i], list2[i])); } print(tuples); // Output: [Tuple(a, 1), Tuple(b, 2), Tuple(c, 3)] // Define the Tuple class class Tuple { final dynamic item1; final dynamic item2; Tuple(this.item1, this.item2); @override String toString() { return 'Tuple($item1, $item2)'; } }

  4. Merging Two Lists of Objects into a Map

    • Description: This snippet demonstrates how to merge two lists of objects into a map where one list represents keys and the other represents values.
    • Code:
      List<String> list1 = ['x', 'y', 'z']; List<int> list2 = [10, 20, 30]; Map<String, int> map = Map.fromIterables(list1, list2); print(map); // Output: {x: 10, y: 20, z: 30}

  5. Mapping Two Lists into a Custom Data Structure in Flutter

    • Description: This snippet shows how to map two lists into a custom data structure or class in Flutter.
    • Code:
      class Person { final String name; final int age; Person(this.name, this.age); @override String toString() { return 'Person(name: $name, age: $age)'; } } List<String> names = ['Alice', 'Bob', 'Charlie']; List<int> ages = [25, 30, 35]; List<Person> people = []; for (var i = 0; i < names.length; i++) { people.add(Person(names[i], ages[i])); } print(people); // Output: [Person(name: Alice, age: 25), Person(name: Bob, age: 30), Person(name: Charlie, age: 35)]

  6. Creating a Dictionary from Two Lists with Default Values in Flutter

    • Description: This snippet shows how to create a dictionary from two lists with default values for missing items.
    • Code:
      List<String> keys = ['name', 'age', 'country']; List<dynamic> values = ['John', 25]; // Missing one value Map<String, dynamic> map = { for (int i = 0; i < keys.length; i++) keys[i]: i < values.length ? values[i] : 'N/A' // Default value }; print(map); // Output: {name: John, age: 25, country: N/A}

  7. Mapping Two Lists into a List of Dictionaries in Flutter

    • Description: This code snippet demonstrates how to map two lists into a list of dictionaries in Flutter.
    • Code:
      List<String> keys = ['name', 'city']; List<dynamic> values = [['Alice', 'Bob'], ['New York', 'Los Angeles']]; List<Map<String, dynamic>> listOfMaps = []; for (var i = 0; i < values[0].length; i++) { Map<String, dynamic> map = { for (int j = 0; j < keys.length; j++) keys[j]: values[j][i] }; listOfMaps.add(map); } print(listOfMaps); // Output: [{name: Alice, city: New York}, {name: Bob, city: Los Angeles}]

  8. Creating a Map from Two Lists with Custom Key Transformations

    • Description: This snippet shows how to create a map from two lists with custom key transformations in Flutter.
    • Code:
      List<String> keys = ['a', 'b', 'c']; List<int> values = [1, 2, 3]; // Custom key transformation Map<String, int> map = { for (var i = 0; i < keys.length; i++) keys[i].toUpperCase(): values[i] // Transforming keys to uppercase }; print(map); // Output: {A: 1, B: 2, C: 3}

  9. Mapping Two Lists into a Dictionary with Type Safety

    • Description: This code snippet demonstrates how to map two lists into a dictionary with type safety using generics in Flutter.
    • Code:
      List<String> keys = ['one', 'two', 'three']; List<int> values = [1, 2, 3]; Map<String, int> map = Map<String, int>.fromIterables(keys, values); print(map); // Output: {one: 1, two: 2, three: 3}

  10. Mapping Two Lists to Create a Dictionary with Specific Conditions

    • Description: This snippet demonstrates how to map two lists into a dictionary with specific conditions or constraints.
    • Code:
      List<String> keys = ['k1', 'k2', 'k3']; List<int> values = [10, 20, 30]; Map<String, int> map = {}; for (int i = 0; i < keys.length; i++) { if (values[i] > 15) { // Only add items where the value is greater than 15 map[keys[i]] = values[i]; } } print(map); // Output: {k2: 20, k3: 30}

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