Maps in Dart

Maps

In a map, data is stored in the form of keys and values. Key occurs only once but we can use the same value multiple times. They are similar to HashMaps and Dictionaries in other languages.

How To Create Map In Dart

Here we are creating a map for String and String. You can create a map of any type.

void main(){
Map<String, String> countryCapital = {
  'USA': 'Washington, D.C.',
  'India': 'New Delhi',
  'China': 'Beijing'
};
  print(countryCapital);
}

Show Output

Here Usa India and China are keys and keys of map should be unique.

Access Value From Key

You can access value from the key. Here we are printing Washington, D.C. by its key i.e USA.

void main(){
Map<String, String> countryCapital = {
  'USA': 'Washington, D.C.',
  'India': 'New Delhi',
  'China': 'Beijing'
};
  print(countryCapital["USA"]);
}

Show Output

Adding Element To Map

void main(){
Map<String, String> countryCapital = {
  'USA': 'Washington, D.C.',
  'India': 'New Delhi',
  'China': 'Beijing'
};
  // Adding New Item
  countryCapital['Japan'] = 'Tokio';
  print(countryCapital);
}

Show Output

Updating An Element Of Map

void main(){
Map<String, String> countryCapital = {
  'USA': 'Nothing',
  'India': 'New Delhi',
  'China': 'Beijing'
};
  // Updating Item
  countryCapital['USA'] = 'Washington, D.C.';
  print(countryCapital);
}

Show Output

Removing Items From MAP

void main(){
Map<String, String> countryCapital = {
  'USA': 'Nothing',
  'India': 'New Delhi',
  'China': 'Beijing'
};
  
  countryCapital.remove("USA");
  print(countryCapital);
}

Show Output

MAP Properties In Dart

Properties	Work
isEmpty	Return true or false.
isNotEmpty	Return true or false.
keys	To get all keys.
values	To get all values.
values.toList()	Convert all maps values to List.
containsKey(‘key’)	Return true or false.
containsValue(‘value’)	Return true or false.

Looping Over Element Of Map

void main(){

  Map<String, dynamic> book = {
    'title': 'Misson Mangal',
    'author': 'Kuber Singh',
    'page': 233
  };
  
 // Loop Through Map
  for(MapEntry book in book.entries){
    print('Key is ${book.key}, value ${book.value}');
  }
  
}

Show Output

Looping In Map Using For Each

void main(){

  Map<String, dynamic> book = {
    'title': 'Misson Mangal',
    'author': 'Kuber Singh',
    'page': 233
  };
  
  
 // Loop Through For Each
  book.forEach((key,value)=> print('Key is $key and value is $value'));
  
}

Show Output