Imagine you have a box of labeled jars. Each jar has a unique label (key), and inside each jar, there's something different (value). For example:
Jar labeled "Apple" contains 5 apples.
Jar labeled "Banana" contains 3 bananas.
Jar labeled "Orange" contains 2 oranges.
Here, the labels ("Apple", "Banana", "Orange") are like keys in a Dart Map, and the contents of each jar (5 apples, 3 bananas, 2 oranges) are the corresponding values. Just like in Dart Maps, each label (key) is unique, and you can easily find out what's inside a jar (value) by reading its label (key).
So, in essence, a Dart Map is like your box of labeled jars, making it easy to organize and access different items quickly.
void main() {
// Using map literal
var fruits = {'Apple':5, 'Banana':3, 'Orange':2};
Creating Dart Maps:
// Using Map literal
var fruits = {'apple': 5, 'banana': 3, 'orange': 2};
// Using Map constructor
var vegetables = Map<String, int>();
vegetables['carrot'] = 30;
vegetables['broccoli'] = 25;
Accessing Values in Dart Maps
Accessing values in a Dart Map is simple. You can retrieve a value associated with a key using the square bracket notation [] or using the forEach method to iterate over all key-value pairs.
print(fruits['apple']); // Output: 5
fruits.forEach((key, value) {
print('$key : $value');
});
Modifying Dart Maps
Dart Maps provide various methods to modify their contents. You can add new key-value pairs, remove existing ones, or update values associated with keys.
fruits['grapes'] = 12; // Adding a new key-value pair
fruits.remove('banana'); // Removing a key-value pair
fruits['apple'] = 15; // Updating the value associated with the 'apple' key
Dart Map Properties and Methods
Dart Maps come with several properties and methods to facilitate data manipulation. Some commonly used ones include:
length: Returns the number of key-value pairs in the Map.keys: Returns an iterable containing all keys in the Map.values: Returns an iterable containing all values in the Map.containsKey(key): Returns true if the Map contains the specified key.