.length

In Dart, the .length property is a utility for determining the number of key-value pairs contained within a Map instance. It enables developers to efficiently manage and manipulate data structures by providing a quick and reliable means of accessing the size of a Map.

Syntax

Map-variable.length

• Map-variable: It represents a variable that holds a Map object.

Example 1

In the following example, the .length property is used to get the key-value pairs of a Map instance that uses similar data types:

void main() {
  Map<String, String> countries = {
    'USA': 'United States',
    'IRE': 'Ireland',
    'ITLY': 'Italy'
  };

  print(countries.length);
}

Here is the output for the above example:

3

Example 2

The .length property can take different data types for its key-value pairs as well:

void main() {
  Map<String, int> fruits = {
    'Apple': 3,
    'Banana': 2,
    'Mango': 9
  };

  print(fruits.length);
}

The output for the above example is as follows:

3

Example 3

The .length property also takes duplicate keys into account and ensures that they are not counted:

void main() {
  Map<String, int> fruits = {
    'Apple': 3,
    'Banana': 2,
    'Apple': 1
  };

  print(fruits.length);
}

The above example will produce the following output:

2