Functions in Dart

Function In Dart

In this tutorial, you will learn about functions in dart. Functions are the block of code that performs a specific task. They are created when some statements are repeatedly occurring in the program. The function helps reusability of the code in the program.

Function Advantages

• Avoid Code Repetition
• Easy to divide the complex program into smaller parts
• Helps to write a clean code

Syntax

returntype functionName(parameter1,parameter2, ...){
  // function body
}

Return type: It tells you the function output type. It can be void, String, int, double, etc. If the function doesn’t return anything, you can use void as the return type.

Function Name: You can name functions by almost any name. Always follow a lowerCamelCase naming convention like void printName().

Parameters: Parameters are the input to the function, which you can write inside the bracket (). Always follow a lowerCamelCase naming convention for your function parameter.

Example 1: Function That Prints Name

This is a simple program that prints name using function. The name of function is printName().

// writing function outside main function.
void printName(){
  print("My name is Raj Sharma. I am from function.");
}
// this is our main function.
void main(){
  printName();
}

My name is Raj Sharma. I am from function.

Example 2: Function To Find Sum of Two Numbers

This function finds the sum of two numbers. Here, the function accepts two parameters. i.e., num1 and num2, and the return type is void.

void add(int num1, int num2){
  int sum = num1 + num2;
   print("The sum is $sum");
}

void main(){
  add(10, 20);
}

The sum is 30

Example 3: Function That Find Simple Interest

This function finds simple interest from principal, time and rate and display result.

// function that calculate interest
void calculateInterest(double principal, double rate, double time) {
  double interest = principal * rate * time / 100;
  print("Simple interest is $interest");
}

void main() {
  double principal = 5000;
  double time = 3;
  double rate = 3;
  calculateInterest(principal, rate, time);
}

Simple interest is 450.0

Challenge

Create a function that finds a cube of numbers.

Key Points

• In dart function are also objects.
• You should follow the lowerCamelCase naming convention while naming function.
• You should follow the lowerCamelCase naming convention while naming function parameters.

About lowerCamelCase

Name should start with lower-case, and every second word’s first letter will be upper-case like num1, fullName, isMarried, etc. Technically, this naming convention is called lowerCamelCase.

Function Parameters Vs Arguments

Many programmers are often confused about parameters and arguments. Let’s have a look at this example.

// Here num1 and num2 are parameters
void add(int num1, int num2){
  int sum;
  sum = num1 + num2;
   
  print("The sum is $sum");
}

void main(){
// Here 10 and 20 are arguments
  add(10, 20);
}

The sum is 30

• Here in add(int num1, int num2), num1 and num2 are parameters and in add(10, 20), 10 and 20 are arguments.
• Parameter is the name and data type you define as an input for your function.
• Argument is the actual value that you passed in.

Video

Watch our video on functions in Dart.