public/subjects/mobile-dev/person

Person

Instructions

Create a class named Person.

Its attributes:

• name - string
• surname - string
• cityOfOrigin - string
• age - int
• height - int

Constructor:

• name - required
• cityOfOrigin - required
• age - required
• height - required
• surname - optional

Object Oriented Programming

Dart supports object oriented programming which Flutter framework relies on. Classes have 2 main concepts: attributes and methods. Attributes are needed to store various data in the instance of Class and methods are functions, which can use Class attributes for various manipulations. To understand OOP and its difference from functional programming visit this website.

Here is an example of the Class in Dart:

class Point {
  double x = 0; // attribute initialized to 0
  double y = 0; // attribute initialized to 0
}

Point - name of the class, x, y - are attributes.

What if you want to initiate a Point with different x and y? To do that declare a Constructor - which is a function that specifies how to create object of a class given a set of parameters.

class Point {
  double x = 0; // attribute
  double y = 0; // attribute

  // Constructor
  Point(double x, double y) {
    this.x = x; // initializing attributes
    this.y = y;
  }
}

In Dart we can also use Constructor declaration of type Constructor(param1, param2...); thus saving a few lines of code if all we want to do is to pass arguments to values.

class Point {
  double x = 0;
  double y = 0;

  Point(this.x, this.y); // "this" is meant for current class.
}

Now let's instantiate two objects of class Point:

var p1 = Point(5, 4);
var p2 = Point(8, 3);

What if we would like to know what is the distance between these 2 points? We can do that by declaring a class function (or method of the class) and passing one of the objects as a parameter:

import 'dart:math';

class Point {
  double x = 0; // field
  double y = 0; // field

Point(double x, double y) { // constructor
    this.x = x; // initializing field
    this.y = y; // initializing field
  }
	// method
	double distanceTo(Point end) {
		return sqrt(pow((end.x - this.x), 2) + pow((end.y - this.y), 2));
	}
}

var p1 = Point(5, 4);
var p2 = Point(8, 3);

print(p1.distanceTo(p2));

• Note: please see the documentation for examples.