Learning Exercise
The primary object-oriented construct in C# is the class, which is a combination of data (fields) and behavior (methods). The fields and methods of a class are known as its members.
Access to members can be restricted through access modifiers, the two most common ones being:
public: the member can be accessed by any code (no restrictions).private: the member can only be accessed by code in the same class.You can think of a class as a template for creating instances of that class. To create an instance of a class (also known as an object), the new keyword is used:
class Car
{
}
// Create two car instances
var myCar = new Car();
var yourCar = new Car();
Fields have a type and can be defined anywhere in a class.
Public fields are defined in PascalCase and private fields are defined in camelCase and prefixed with an underscore _:
class Car
{
// Accessible by anyone
public int Weight;
// Only accessible by code in this class
private string _color;
}
One can optionally assign an initial value to a field. If a field does not specify an initial value, it wll be set to its type's default value. An instance's field values can be accessed and updated using dot-notation.
class Car
{
// Will be set to specified value
public int Weight = 2500;
// Will be set to default value (0)
public int Year;
}
var newCar = new Car();
newCar.Weight; // => 2500
newCar.Year; // => 0
// Update value of the field
newCar.Year = 2018;
Private fields are usually updated as a side-effect of calling a method. Such methods usually don't return any value, in which case the return type should be void:
class CarImporter
{
private int _carsImported;
public void ImportCars(int numberOfCars)
{
// Update private field from public method
_carsImported = _carsImported + numberOfCars;
}
}
In this exercise you'll be playing around with a remote controlled car, which you've finally saved enough money for to buy.
Cars start with full (100%) batteries. Each time you drive the car using the remote control, it covers 20 meters and drains one percent of the battery.
The remote controlled car has a fancy LED display that shows two bits of information:
"Driven <METERS> meters"."Battery at <PERCENTAGE>%".If the battery is at 0%, you can't drive the car anymore and the battery display will show "Battery empty".
You have six tasks, each of which will work with remote controlled car instances.
Implement the (static) RemoteControlCar.Buy() method to return a brand-new remote controlled car instance:
RemoteControlCar car = RemoteControlCar.Buy();
Implement the RemoteControlCar.DistanceDisplay() method to return the distance as displayed on the LED display:
var car = RemoteControlCar.Buy();
car.DistanceDisplay();
// => "Driven 0 meters"
Implement the RemoteControlCar.BatteryDisplay() method to return the battery percentage as displayed on the LED display:
var car = RemoteControlCar.Buy();
car.BatteryDisplay();
// => "Battery at 100%"
Implement the RemoteControlCar.Drive() method that updates the number of meters driven:
var car = RemoteControlCar.Buy();
car.Drive();
car.Drive();
car.DistanceDisplay();
// => "Driven 40 meters"
Update the RemoteControlCar.Drive() method to update the battery percentage:
var car = RemoteControlCar.Buy();
car.Drive();
car.Drive();
car.BatteryDisplay();
// => "Battery at 98%"
Update the RemoteControlCar.Drive() method to not increase the distance driven nor decrease the battery percentage when the battery is drained (at 0%):
var car = RemoteControlCar.Buy();
// Drain the battery
// ...
car.DistanceDisplay();
// => "Driven 2000 meters"
car.BatteryDisplay();
// => "Battery empty"
Edit via GitHub
Sign up to Exercism to learn and master C# with 62 concepts, 167 exercises, and real human mentoring, all for free.