Dart Sets

Sets data type in Dart

A set is an unordered collection of items that are unique. Dart infers that sets tale strings as values.

Example,

var languages = { ‘Dart’ , ‘Flutter’, ‘Python’, ‘Java’ };

There are some salient functions that can be used along with sets,

1. add( ) or addAll( ) methods are the functions used to add elements in the existing set.
2. .length is used to extract the number of items in the set.

Program:

void main( )
{
    // declares and defines set languages
    var languages = { 'Dart' , 'Flutter' , 'Python' , 'Java' };
    // prints the values of set
    print( languages );
    
    // creates an empty string
    var lang = < String > {  };
    print( lang );
    // add( ) to add the value in set languages
    languages.add( 'php' );
    print( languages );
  }

Output :

{Dart, Flutter, Python, Java}
{}
{Dart, Flutter, Python, Java, php}

Set Operations in Dart

1. Union = This operation merges two strings and returns the merged string.
2. Intersection = This operation returns the common strings out of the two strings.
3. Difference ( string A, string B ) = This operation returns the string present in string A but not in B.

Consider the following code in Dart that illustrates the above operations:

Program

// Set Operations in Dart
 
void main( )
{
  // declaring set 1 with string values
  var set1 = < String > { "India", "will", "win", "T-20" };
   
  // printing the values of set 1
  print( " Set 1 is as follows : " );
  print( set1 );
   
   
  // declaring set 2 with string values
  var set2 = < String > { "World", "Cup", "this", "year." };
  
  // declaring set 3 with string values
  var set3 = < String > { "World", "India", "win", "year." };
   
  // printing the values of set 2
  print( "\n\n Set 2 is as follows : " );
  print( set2 );
   
   
  // Performing union on set1 and set2
  print( "\n Union of two sets is ${ set1.union( set2 ) } \n " ) ;
   
  // Performing intersection on set1 and set2
  print( " Intersection of sets 1 and 2 is  ${ set1.intersection( set2 ) } \n ");
  
  // Performing intersection on set2 and set3
  print( " Intersection of sets 2 and 3 is ${ set2.intersection( set3 ) } \n " );
   
  // Performing difference ( Set2 - Set1 )
  print( " Difference of sets 2 and 1 is ${ set2.difference( set1 ) } \n " );
  
  // Performing difference ( Set1 - Set2 )
  print( " Difference of sets 1 and 2 is ${ set1.difference( set2 ) } \n " );
  
  // Performing difference ( Set2 - Set3 )
  print( " Difference of sets 2 and 3 is ${ set2.difference( set3 ) } \n " );
     
}

Output

Set 1 is as follows : 
{India, will, win, T-20}


 Set 2 is as follows : 
{World, Cup, this, year.}


 Union of two sets is {India, will, win, T-20, World, Cup, this, year.} 
 Intersection of sets 1 and 2 is  {} 
 Intersection of sets 2 and 3 is {World, year.} 
 Difference of sets 2 and 1 is {World, Cup, this, year.} 
 Difference of sets 1 and 2 is {India, will, win, T-20} 
 Difference of sets 2 and 3 is {Cup, this}

Sets Functions

S. No.	Syntax	Description
1.	variable_name.elementAt( index );	Returns the element present at the particular index, passed as an argument.
2.	variable_name.length;	Calculates the length of the set, and returns the same.
3.	variable_name.contains( element_name );	Checks if the element_name is present in the set or not, and returns true or false accordingly.
4.	variable_name.remove( element_name );	Deletes the element that is passed as an argument to the function.
5.	variable_name.forEach(…);	Implements the command defined inside forEach( ) function for all the elements inside the set.
6.	variable_name.clear( );	Deletes all the element inside the set.