How to Check if a Key Exists in a Map in Dart - Step by Step Examples

How to Check if a Key Exists in a Map in Dart ?

Answer

To check if a key exists in a map in Dart, you can use the containsKey method. This method returns a boolean value indicating whether the map contains the specified key.

✐ Examples

1 Checking if a Key Exists Using containsKey Method

We can check if a key exists in a map in Dart using the containsKey method, which returns true if the map contains the specified key and false otherwise.

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 containsKey method to check for a specific key in the map. The containsKey method returns a boolean value indicating whether the map contains the specified key.
We print the result 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
    };

    // Check if a key exists using containsKey method
    bool keyExists = myMap.containsKey('two');

    // Print the result
    print('Does key "two" exist? $keyExists');
}

Output

Does key "two" exist? true

2 Checking if a Key Does Not Exist Using containsKey Method

We can check if a key does not exist in a map in Dart using the containsKey method, which returns false if the map does not contain 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 containsKey method to check for a specific key in the map. The containsKey method returns a boolean value indicating whether the map contains the specified key.
We print the result 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
    };

    // Check if a key does not exist using containsKey method
    bool keyExists = myMap.containsKey('four');

    // Print the result
    print('Does key "four" exist? $keyExists');
}

Output

Does key "four" exist? false

3 Checking Multiple Keys Using containsKey Method

We can check if multiple keys exist in a map in Dart using the containsKey method, which returns true if the map contains the specified key and false otherwise.

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 containsKey method to check for multiple keys in the map. The containsKey method returns a boolean value indicating whether the map contains the specified key.
We print the results 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
    };

    // Check if multiple keys exist using containsKey method
    bool keyExistsOne = myMap.containsKey('one');
    bool keyExistsFour = myMap.containsKey('four');

    // Print the results
    print('Does key "one" exist? $keyExistsOne');
    print('Does key "four" exist? $keyExistsFour');
}

Output

Does key "one" exist? true
Does key "four" exist? false

Summary

In this tutorial, we learned How to Check if a Key Exists in a Map in Dart language with well detailed examples.

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How to Check if a Key Exists in a Map in Dart - Step by Step Examples