How to Update the Value for a Key in a Map in Dart

How to Update the Value for a Key in a Map in Dart ?

Answer

To update the value for a key in a map in Dart, you can use the subscript operator or the update method. These methods allow you to modify the value associated with a specific key directly.

✐ Examples

1 Updating the Value Using Subscript Operator

We can update the value for a key in a map in Dart using the subscript operator, which allows us to modify the value associated with a specific key directly.

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 subscript operator to update the value for a specific key in the map. The subscript operator allows us to assign a new value to the key.
We print the updated map 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
    };

    // Update the value using subscript operator
    myMap['two'] = 22;

    // Print the updated map
    print(myMap);
}

Output

{one: 1, two: 22, three: 3}

2 Updating the Value Using update Method

We can update the value for a key in a map in Dart using the update method, which allows us to modify the value associated with a specific key directly.

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 update method to update the value for a specific key in the map. The update method takes the key and a function that returns the new value to be assigned.
We print the updated map 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
    };

    // Update the value using update method
    myMap.update('two', (value) => 22);

    // Print the updated map
    print(myMap);
}

Output

{one: 1, two: 22, three: 3}

3 Updating the Value Conditionally Using update Method

We can update the value for a key in a map in Dart using the update method to modify the value associated with it based on a condition.

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 update method to update the value for a specific key in the map based on a condition. The update method takes the key and a function that returns the new value to be assigned.
We print the updated map 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
    };

    // Update the value conditionally using update method
    myMap.update('two', (value) => value == 2 ? 22 : value);

    // Print the updated map
    print(myMap);
}

Output

{one: 1, two: 22, three: 3}

Summary

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

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How to Update the Value for a Key in a Map in Dart