Add new element to map dart

In Dart, you can add a new element to a Map using the putIfAbsent method or the [] operator.

Here are some examples:

Using putIfAbsent method

Map<String, int> myMap = {'a': 1, 'b': 2};

myMap.putIfAbsent('c', () => 3); // adds 'c': 3 to the map if it doesn't exist

print(myMap); // Output: {'a': 1, 'b': 2, 'c': 3}

Using [] operator

Map<String, int> myMap = {'a': 1, 'b': 2};

myMap['c'] = 3; // adds 'c': 3 to the map if it doesn't exist

print(myMap); // Output: {'a': 1, 'b': 2, 'c': 3}

In both cases, if the key 'c' already exists in the map, the value associated with it will be updated.

Note: If you want to add a new element to a Map and return the new value, you can use the putIfAbsent method with a callback function that returns the new value. For example:

Map<String, int> myMap = {'a': 1, 'b': 2};

int newValue = myMap.putIfAbsent('c', () => 3 + 4); // adds 'c': 7 to the map if it doesn't exist

print(myMap); // Output: {'a': 1, 'b': 2, 'c': 7}
print(newValue); // Output: 7