Dart Sets
An unordered collection of various values of the same type is called a dart set. It is unordered yet has much of the same functionality as an array. Duplicate value storage is not permitted by sets. There must be unique values in the set.
It is crucial in situations where we wish to store different types of data in one variable. We can only have values of the same type after the type of the Set is declared. The elements’ order cannot be maintained by the set.
Dart Initializing Set
There are two ways to declare or initialize an empty set in Dart. The set can be declared using the curly braces {} followed by a type argument, or by using the curly braces {} to declare the variable type Set. The following is the syntax for declaring a set.
Syntax
var setName = <type>{};
Or
Set<type> setname = {};
The set variable’s name is indicated by the setname, while the set’s data type is indicated by the type.
Note: Keep in mind that the set’s syntax is very similar to that of the map literals. The Dart compiler will produce a Map object rather than a Set if the type annotation is not defined with {} or the variable it is allocated to.
Example
void main(){
print("Initializing the Set");
var names = <String>{"James","Ricky", "Devansh","Adam"};
print(names);
}
Output
Initializing the Set
{James, Ricky, Devansh, Adam}
Add Element into Set
The add() and addAll() methods in the Dart allow you to add an element to the specified set. The single item is added to the specified set using the add() method. When several elements are added to an existing set using the addAll() method, it can add them one at a time. Below is the syntax.
Syntax
Set_name.add(<value>);
Or
Set_name.addAll(val1,val2....valN)
Example
void main(){
print("Insert element into the Set");
var names = {"James","Ricky","Devansh","Adam"};
// Declaring empty set
var emp = <String>{};
emp.add("Jonathan");
print(emp);
// Adding multiple elements
emp.addAll(names);
print(emp);
}
Output
Insert element into the Set
{Jonathan}
{Jonathan, James, Ricky, Devansh, Adam}
Explanation
Two sets of names and emp have been announced. Emp is an empty set; the set names were composed of few components. Then, we ran the addAll() method and supplied another set of names as an input. We had added the single element “Jonathan” using the add() method. It expanded the emp set by adding the multiple values.
Access the Set Element
The elementAt() function in Dart allows you to retrieve an item by supplying it its given index location. Starting at zero, the set indexing rises to size – 1, where size is the total number of elements in the set. If we enter a larger index number than its allowed size, an error will be raised. Below is the syntax.
Syntax
Set_name.elementAt(index)
Example
void main(){
print("Access element from the Set");
var names = {"James","Ricky","Devansh","Adam"};
print(names);
var x = names.elementAt(3);
print(x);
}
Output
Access element from the Set
{James, Ricky, Devansh, Adam}
Adam
Explanation
The example above uses fixed names. We used the elementAt() function and supplied the parameter for index position 3. The assessed value was placed in a variable called x, and the outcome was printed after that.
Dart Finding Element in Set
The contains() method in Dart is used to locate an element within a set. It takes one item as an input and outputs the result in Boolean format. It returns true if the supplied element is in the set and false otherwise. Below is the syntax.
Syntax
set_name.contains(value);
Example
void main() {
print("Example - Find Element in the given Set");
var names = <String>{"Peter","John","Ricky","Devansh","Finch"};
if(names.contains("Ricky")){
print("Element Found");
}
else {
print("Element not found");
}
}
Output
Example - Find Element in the given Set
Element Found
Explanation
In the program above, we invoked the contains() function and gave the value “Ricky” as an argument in order to find the element in the specified set. To determine whether an element is a part of the specified set or not, we employed the conditional statement. When the specified element was found in the set, the condition was satisfied, and the if block statement was printed.
Note – We will learn conditional statement in the next section.
Dart Remove Set Element
To remove an element from the specified set, use the remove() method. The value is passed in as an argument, and its removal from the specified set is required. Below is the syntax.
Syntax
set_names.contains(value)
Example
void main() {
print("Example - Remove Element in the given Set");
var names = <String>{"Peter", "John", "Ricky", "Devansh", "Finch"};
print("Before remove : ${names}");
names.remove("Peter");
print("After remove : ${names}");
}
Output
Example - Remove Element in the given Set
Before remove : {Peter, John, Ricky, Devansh, Finch}
After remove : {John, Ricky, Devansh, Finch}
Explanation
Using the remove() method, we eliminated “Peter” from the provided set in the application above. The updated set object was given back.
Dart Iterating Over a Set Element
The forEach method in Dart can be used to iterate the set element as follows:
Example
void main() {
print("Example - Remove Element in the given Set");
var names = <String>{"Peter","John","Ricky","Devansh","Finch"};
names.forEach((value) {
print('Value: $value');
});
}
Output
Example - Remove Element in the given Set
Value: Peter
Value: John
Value: Ricky
Value: Devansh
Value: Finch
Dart Remove All Set Element
By using the clear() techniques, we can eliminate the entire set element. It returns an empty set after deleting or removing every element from the supplied set. The following is the syntax:
Syntax
set_name.clear();
Example
void main() {
print("Example - Remove All Element to the given Set");
var names = <String>{"Peter","John","Ricky","Devansh","Finch"};
names.clear();
print(names);
}
Output
Example - Remove All Element to the given Set
{Peter, John, Ricky, Devansh, Finch}
{}
TypeCast Set to List
The toList() method can be used to transform a Set object into a List object. The following is the syntax.
Note: The types of Lists and Sets must match exactly.
Syntax
List<type> <list_name> = <set_name>. toList();
Dart Set Operations
The Dart Set offers the ability to carry out the subsequent set actions. Below is a list of these operations.
Union: The value of the two supplied sets, a and b, is combined by the union.
Intersection: All components that are shared by both sets are returned when set a and set b intersect.
Subtraction: When two sets, a and b, are subtracted, the result is a-b, or the element of set b that is absent from set a.
Example
void main() {
var x = <int>{10,11,12,13,14,15};
var y = <int>{12,18,29,43};
var z = <int>{2,5,10,11,32};
print("Example - Set Operations");
print("x union y is -");
print(x.union(y));
print("x intersection y is - ");
print(x.intersection(y));
print("y difference z is - ");
print(y.difference(z));
}
Output
Example - Set Operations
x union y is -
{10, 11, 12, 13, 14, 15, 18, 29, 43}
x intersection y is -
{12}
y difference z is -
{12, 18, 29, 43}
Dart Set Properties
The following are the few attributes of the Dart set.
| Properties | Explanations |
|---|---|
| first | It is used to get the first element in the given set. |
| isEmpty | If the set does not contain any element, it returns true. |
| isNotEmpty | If the set contains at least one element, it returns true |
| length | It returns the length of the given set. |
| last | It is used to get the last element in the given set. |
| hashcode | It is used to get the hash code for the corresponding object. |
| Single | It is used to check whether a set contains only one element. |
