Dart – Functions
The function is a set of statements that take inputs, do some specific computation and produces output. Functions are created when certain statements are repeatedly occurring in the program and a function is created to replace them. Functions make it easy to divide the complex program into smaller sub-groups and increase the code reusability of the program.
Defining the Function in Dart
Dart provides us with the facility of using functions in its program.
In the above syntax:
- function_name: defines the name of the function.
- return_type: defines the datatype in which output is going to come.
- return value: defines the value to be returned from the function.
How to Call Functions in Dart?
In the above syntax:
- function_name: defines the name of the function.
- argument list: is the list of the parameters that the function requires.
Example 1: Complete function in Dart
int add(int a, int b){
// Creating function
int result = a + b;
// returning value result
return result;
}
void main(){
// Calling the function
var output = add(10, 20);
// Printing output
print(output);
}
Output:
30
Note: You must note that two functions can’t have the same function name although they differ in parameters.
Example 2: Function without parameter and return value.
void GFG(){
// Creating function
print("Welcome to w3wiki");
}
void main()
{
// Calling the function
GFG();
}
Output:
Welcome to w3wiki
Note: You must note that you can also directly return string or integer or any output of expression through the return statement.
Functions with Optional Parameter
There are also optional parameter system in Dart which allows user to give some optional parameters inside the function.
| Sr. No. | Parameter | Description |
|---|---|---|
| 1. | Optional Positional Parameter | To specify it use square (‘[ ]’) brackets |
| 2. | Optional Named parameter | When we pass this parameter it is mandatory to pass it while passing values. It is specify by curly(‘{ }’) brackets. |
| 3. | Optional parameter with default values | Here parameters are assign with default values. |
Example:
void gfg1(int g1, [ var g2 ])
{
// Creating function 1
print("g1 is $g1");
print("g2 is $g2");
}
void gfg2(int g1, { var g2, var g3 })
{
// Creating function 1
print("g1 is $g1");
print("g2 is $g2");
print("g3 is $g3");
}
void gfg3(int g1, { int g2 : 12 })
{
// Creating function 1
print("g1 is $g1");
print("g2 is $g2");
}
void main()
{
// Calling the function with optional parameter
print("Calling the function with optional parameter:");
gfg1(01);
// Calling the function with Optional Named parameter
print("Calling the function with Optional Named parameter:");
gfg2(01, g3 : 12);
// Calling function with default valued parameter
print("Calling function with default valued parameter");
gfg3(01);
}
Output:
Calling the function with optional parameter:
g1 is 1
g2 is null
Calling the function with Optional Named parameter:
g1 is 1
g2 is null
g3 is 12
Calling function with default valued parameter
g1 is 1
g2 is 12
Recursive Function in Dart
The recursive function is those functions in which function calls itself. It is a good way to avoid repeatedly calling the same function to get the output.
Example: Recursive function for fibonacci series.
/// Computes the nth Fibonacci number.
int fibonacci(int n)
{
// This is recursive function as it calls itself
return n < 2 ? n : (fibonacci(n - 1) + fibonacci(n - 2));
}
void main()
{
// input
var i = 20;
print('fibonacci($i) = ${fibonacci(i)}');
}
Output:
For input as 20
fibonacci(20) = 6765
Lambda Function in Dart
They are the short way of representing a function in Dart. They are also called arrow function. But you should note that with lambda function you can return value for only one expression.
Example: Lambda function in dart.
// Lambda function in Dart
void gfg() => print("Welcome to w3wiki");
void main()
{
// Calling Lambda function
gfg();
}
Output:
Welcome to w3wiki
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