Dart Queue reduce function example

Dart Queue reduce function:

The reduce function will reduce one queue to a single value, it takes one combine function and it combines all elements to a single value. In this post, we will learn how reduce function works with different examples.

Syntax of the reduce function:

The syntax of the reduce function is:

reduce(E combine(E value, E element)) → E

It takes one function combine and with the help of this function, it will reduce the queue elements to a single value. It is a method defined for dart iterable. It starts with the first element and uses the combine function to combine all other values to reduce it to a single value. If the queue has only one element, it will return that element.

Example of the reduce function to find the sum of all values:

The following program uses the reduce method to find the sum of all digits of the given queue:

import 'dart:collection';

void main() {
  var q = Queue.of([1, 2, 3, 4, 5]);
  print("Given queue: ${q}");

  var sum = q.reduce((v, e)=> v + e);
  print("Sum: ${sum}");
}

In this program, q is the given queue of numbers. The reduce function returns the sum of the two values passed as its parameters.

If you run this program, it will print:

Given queue: {1, 2, 3, 4, 5}
Modified queue: 15

As you can see here, it is printing the total sum of the digits of the queue.

Example of the reduce function with objects:

Let’s try the reduce function with a queue of objects:

import 'dart:collection';

class Item {
  String? name;
  int? price;

  Item(String name, int price) {
    this.name = name;
    this.price = price;
  }
}

void main() {
  var q =
      Queue.of([Item("Item-1", 100), Item("Item-2", 24), Item("Item-3", 55)]);

  var result =
      q.reduce((value, element) => Item("", value.price! + element.price!));
  print("Sum of all prices: ${result.price}");
}

Here,

Item is a class to hold the name and price of an item.
We created one queue, q, of three different items with different prices.
The combine function should return a Item object. It adds the price of both value and element objects and creates a new object.
The reduced value is assigned to the result variable.

If you run this program, it will print:

Sum of all prices: 179

i.e. the final Item variable holds the sum of the prices of all the objects.

Refer:

Flutter Queue Doc

CodeVsColor

Dart Queue reduce function example