How to Sort a Map by Values in Dart - Step by Step Examples

How to Sort a Map by Values in Dart ?

Answer

To sort a map by values in Dart, you can convert the map to a list of key-value pairs, sort the list by values, and then convert it back to a map. This method provides a straightforward way to sort the map based on values.

✐ Examples

1 Sorting a Map by Values Using List Conversion

We can sort a map by values in Dart by converting the map to a list of key-value pairs, sorting the list by values, and then converting it back to a map.

For example,

We start by declaring and initializing a map named myMap with some key-value pairs. In this example, the map has string keys and integer values.
We convert the map to a list of key-value pairs using the entries.toList method.
We sort the list by values using the sort method with a custom comparator.
We create a new map from the sorted list using the Map.fromEntries method.
We print the sorted map to the console using the print function to verify the sorting.

Dart Program

void main() {
    // Declare and initialize a map
    Map<String, int> myMap = {
        'apple': 3,
        'banana': 1,
        'cherry': 2
    };

    // Convert the map to a list of key-value pairs
    var sortedEntries = myMap.entries.toList()
      ..sort((a, b) => a.value.compareTo(b.value));

    // Create a new map from the sorted list of key-value pairs
    Map<String, int> sortedMap = Map.fromEntries(sortedEntries);

    // Print the sorted map
    print('Sorted Map by Values:');
    sortedMap.forEach((key, value) => print('$key: $value'));
}

Output

Sorted Map by Values:
banana: 1
cherry: 2
apple: 3

2 Sorting a Map by Values in Descending Order

We can sort a map by values in descending order in Dart by converting the map to a list of key-value pairs, sorting the list by values in descending order, and then converting it back to a map.

For example,

We start by declaring and initializing a map named myMap with some key-value pairs. In this example, the map has string keys and integer values.
We convert the map to a list of key-value pairs using the entries.toList method.
We sort the list by values in descending order using the sort method with a custom comparator.
We create a new map from the sorted list using the Map.fromEntries method.
We print the sorted map to the console using the print function to verify the sorting.

Dart Program

void main() {
    // Declare and initialize a map
    Map<String, int> myMap = {
        'apple': 3,
        'banana': 1,
        'cherry': 2
    };

    // Convert the map to a list of key-value pairs
    var sortedEntries = myMap.entries.toList()
      ..sort((a, b) => b.value.compareTo(a.value));

    // Create a new map from the sorted list of key-value pairs
    Map<String, int> sortedMap = Map.fromEntries(sortedEntries);

    // Print the sorted map
    print('Sorted Map by Values (Descending):');
    sortedMap.forEach((key, value) => print('$key: $value'));
}

Output

Sorted Map by Values (Descending):
apple: 3
cherry: 2
banana: 1

3 Sorting a Map with Numeric Keys by Values

We can sort a map with numeric keys by values in Dart by converting the map to a list of key-value pairs, sorting the list by values, and then converting it back to a map.

For example,

We start by declaring and initializing a map named myMap with some key-value pairs. In this example, the map has integer keys and string values.
We convert the map to a list of key-value pairs using the entries.toList method.
We sort the list by values using the sort method with a custom comparator.
We create a new map from the sorted list using the Map.fromEntries method.
We print the sorted map to the console using the print function to verify the sorting.

Dart Program

void main() {
    // Declare and initialize a map
    Map<int, String> myMap = {
        3: 'three',
        1: 'one',
        2: 'two'
    };

    // Convert the map to a list of key-value pairs
    var sortedEntries = myMap.entries.toList()
      ..sort((a, b) => a.value.compareTo(b.value));

    // Create a new map from the sorted list of key-value pairs
    Map<int, String> sortedMap = Map.fromEntries(sortedEntries);

    // Print the sorted map
    print('Sorted Map by Values:');
    sortedMap.forEach((key, value) => print('$key: $value'));
}

Output

Sorted Map by Values:
1: one
2: two
3: three

Summary

In this tutorial, we learned How to Sort a Map by Values in Dart language with well detailed examples.

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How to Sort a Map by Values in Dart - Step by Step Examples