Functions - Introduction to Dart

main.dart

import 'package:flutter/material.dart';


//Variables
const double pi = 3.14;

void main() {
  showPerimeter();//calling method with no parameters
  showPerimeterWithRadius(80);//calling method with parameter
  double result = perimeter();
  print(result);
  var result2 = perimeterWithRadius(100);
  print("Perimeter is $result2");
  showPerimeterWithMultiple("Perimeter of circle with multiple parameters and radius of", 120);
  
  showVolume(length: 20, breadth: 30, height: 80);
  //showVolume();//fix issue with default parameters
  //showVolume(length: 20, breadth: 30);
  //showVolume(height: 80);
  
  
  showCubeVolume(length: 60);
  
  showArea();
  showArea(3, 5);
  
  print(anyArea(40));
  print(anyArea(25, breadth: 32));
  print(anyArea(13, breadth: 7, height: 91));
  
  sendMessage("Olaide", "Damilola");
  sendMessage("Esther", "Imole", "Hello World!!!");
}

//Methods

void showPerimeter() {
  int radius = 70;
  double result = 2 * pi * radius;
  print("Perimeter of circle with radius of $radius is $result");
}


//Method with parameter

void showPerimeterWithRadius(int radius) {
  double result = 2 * pi * radius;
  print(
      "Perimeter of circle with parameter radius of $radius is ${result.toStringAsFixed(2)}");
}



//Method with return type

double perimeter() {
  return 2 * pi * 70;
}

//Method with required position parameter and return type

double perimeterWithRadius(int radius) {
  return 2 * pi * 70;
}

//Methods with required position multiple parameters

void showPerimeterWithMultiple(String prefix, int radius) {
  double result = 2 * pi * radius;
  print("$prefix $radius is ${result.toStringAsFixed(2)}");
}


//Methods with Named optional parameters

void showVolume({int length, int breadth, int height}) {
  var result = length * breadth * height;
  print("The volume is $result");
}


void showCubeVolume({@required int length}){
  showVolume(breadth: length, height: length, length: length);
}

//Methods with Optional Positional parameters


void showArea([int length = 1, int breadth = 1]){
  print("the area is ${length * breadth}");
}



//methods with combined parameters

int anyArea(int length, {int breadth = 1, int height = 1}){
  return length * breadth * height;
}


void sendMessage(String sender, String receiver, [String message = "Ping"]){
  print("Message from $sender to $receiver is: $message");
}