How to Filter a Map Based on Values in Dart

How to Filter a Map Based on Values in Dart ?

Answer

To filter a map based on values in Dart, you can iterate over the map and add key-value pairs that meet the filter criteria to a new map. This method allows you to create a subset of the original map based on specific value conditions.

✐ Examples

1 Filtering a Map Based on Value Range

We can filter a map based on a range of values in Dart by iterating over the map and adding key-value pairs that fall within the specified range to a new 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 integer values.
We declare an empty map named filteredMap to store the filtered key-value pairs.
We define the lower and upper bounds of the value range.
We iterate over the original map using the forEach method and check if each value falls within the specified range.
We add the key-value pairs that meet the condition to the filteredMap.
We print the filtered map to the console using the print function to verify the filtering.

Dart Program

void main() {
    // Declare and initialize a map
    Map<int, int> myMap = {
        1: 10,
        2: 20,
        3: 30,
        4: 40,
        5: 50
    };

    // Declare an empty map to store the filtered key-value pairs
    Map<int, int> filteredMap = {};

    // Define the value range
    int lowerBound = 20;
    int upperBound = 40;

    // Iterate over the original map and filter based on the value range
    myMap.forEach((key, value) {
        if (value >= lowerBound && value <= upperBound) {
            filteredMap[key] = value;
        }
    });

    // Print the filtered map
    print('Filtered Map by Value Range:');
    filteredMap.forEach((key, value) => print('$key: $value'));
}

Output

Filtered Map by Value Range:
2: 20
3: 30
4: 40

2 Filtering a Map Based on Specific Values

We can filter a map based on specific values in Dart by iterating over the map and adding key-value pairs that match the specified values to a new 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 integer values.
We declare an empty map named filteredMap to store the filtered key-value pairs.
We define a set of specific values that we want to filter the map by.
We iterate over the original map using the forEach method and check if each value matches one of the specified values.
We add the key-value pairs that meet the condition to the filteredMap.
We print the filtered map to the console using the print function to verify the filtering.

Dart Program

void main() {
    // Declare and initialize a map
    Map<int, int> myMap = {
        1: 10,
        2: 20,
        3: 30,
        4: 40,
        5: 50
    };

    // Declare an empty map to store the filtered key-value pairs
    Map<int, int> filteredMap = {};

    // Define the specific values to filter by
    Set<int> valuesToFilter = {10, 30, 50};

    // Iterate over the original map and filter based on the specific values
    myMap.forEach((key, value) {
        if (valuesToFilter.contains(value)) {
            filteredMap[key] = value;
        }
    });

    // Print the filtered map
    print('Filtered Map by Specific Values:');
    filteredMap.forEach((key, value) => print('$key: $value'));
}

Output

Filtered Map by Specific Values:
1: 10
3: 30
5: 50

3 Filtering a Map with String Values Based on Prefix

We can filter a map with string values based on a specific prefix in Dart by iterating over the map and adding key-value pairs that have values starting with the given prefix to a new 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 declare an empty map named filteredMap to store the filtered key-value pairs.
We define a prefix string that we want to filter the map by.
We iterate over the original map using the forEach method and check if each value starts with the specified prefix.
We add the key-value pairs that meet the condition to the filteredMap.
We print the filtered map to the console using the print function to verify the filtering.

Dart Program

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

    // Declare an empty map to store the filtered key-value pairs
    Map<int, String> filteredMap = {};

    // Define the prefix to filter by
    String prefix = 'ap';

    // Iterate over the original map and filter based on the prefix
    myMap.forEach((key, value) {
        if (value.startsWith(prefix)) {
            filteredMap[key] = value;
        }
    });

    // Print the filtered map
    print('Filtered Map by Prefix:');
    filteredMap.forEach((key, value) => print('$key: $value'));
}

Output

Filtered Map by Prefix:
1: apple
3: apricot

Summary

In this tutorial, we learned How to Filter a Map Based on Values in Dart language with well detailed examples.

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How to Filter a Map Based on Values in Dart