How to Get the Value Associated with a Key in a Map in Dart

How to Get the Value Associated with a Key in a Map in Dart ?

Answer

To get the value associated with a key in a map in Dart, you can use the square bracket notation or the map's lookup method. These methods allow you to access the value directly using the key.

✐ Examples

1 Getting the Value Associated with a Key Using Square Bracket Notation

We can get the value associated with a key in a map in Dart using the square bracket notation, which returns the value associated with the specified key.

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 use the square bracket notation to access the value associated with the key 'two'. The square bracket notation returns the value associated with the specified key.
We store the value in a variable named value.
We print the value to the console using the print function.

Dart Program

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

    // Get the value associated with a key using square bracket notation
    int? value = myMap['two'];

    // Print the value
    print('The value associated with key "two" is: $value');
}

Output

The value associated with key "two" is: 2

2 Getting the Value Associated with a Key Using lookup Method

We can get the value associated with a key in a map in Dart using the lookup method, which returns the value associated with the specified key.

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 use the lookup method to access the value associated with the key 'three'. The lookup method returns the value associated with the specified key.
We store the value in a variable named value.
We print the value to the console using the print function.

Dart Program

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

    // Get the value associated with a key using lookup method
    int? value = myMap['three'];

    // Print the value
    print('The value associated with key "three" is: $value');
}

Output

The value associated with key "three" is: 3

3 Handling Key Not Found Using Square Bracket Notation

We can handle the case where a key is not found in a map in Dart using the square bracket notation, which returns null if the key is not present.

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 use the square bracket notation to attempt to access the value associated with the key 'four'. The square bracket notation returns null if the key is not found.
We store the value in a variable named value.
We check if the value is null and print an appropriate message to the console using the print function.

Dart Program

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

    // Attempt to get the value associated with a non-existent key
    int? value = myMap['four'];

    // Print the result
    if (value == null) {
        print('Key "four" not found in the map.');
    } else {
        print('The value associated with key "four" is: $value');
    }
}

Output

Key "four" not found in the map.

Summary

In this tutorial, we learned How to Get the Value Associated with a Key in a Map in Dart language with well detailed examples.

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How to Get the Value Associated with a Key in a Map in Dart