change order

README.md

@@ -13,13 +13,14 @@ Lessons:
 
 - [instanciating objects, accessing attributes and methods](./lessons/Instances.md)
 - [creating a class](./lessons/Classes.md)
+- [constructors](./lessons/Constructors.md)
 
 Work in progress:
 
-- constructors
+- inheritance
 - encapsulation
 - getter / setter / property
-- inheritance
 - polymorphism
 - virtual classes
 - interfaces
+- Factories

cpp/Instances.md

@@ -0,0 +1,10 @@
+# C++ Example
+
+## Language Specific
+
+c++ is almost identical to java in this example. The only difference here is
+that c++ doesn't require the object to be initialized with the keyword 'new'.
+
+Relevant Files:
+
+- [main.cpp](./classes/main.cpp)

cpp/classes/README.md

@@ -1,7 +1,8 @@
 # Classes in C++
 
 In c++ classes are defined using a header file and the implementation in a
-regular .cpp file. Explanations to the structure can be found in the files themselves
+regular .cpp file. Explanations to the structure can be found in the files
+themselves
 
 ## Relevant files
 

cpp/classes/car.h

@@ -24,11 +24,11 @@ class car
   // define the visibility of the following fields and methods
   // in this case everything is public since visibility is a topic in future lessons
   public:
-    // define two strings, manufacturer and model
+    // define two fields, manufacturer and model
     std::string manufacturer;
     std::string model;
 
-    // define a function that will print out information
+    // define a method that will print out information
     void print_info();
 };
 

cpp/constructors/README.md

@@ -0,0 +1,7 @@
+# Constructors in C++
+
+## Relevant files
+
+- [car.h](./car.h)
+- [car.cpp](./car.cpp)
+- [main.cpp](./main.cpp)

cpp/constructors/car.cpp

@@ -0,0 +1,23 @@
+// include the header file
+#include "car.h"
+
+// include necessary libraries and namespaces
+#include <iostream>
+#include <string>
+using namespace std;
+
+// define the implementation for car.print_info()
+void car::print_info()
+{
+  cout << "Car Information:" << endl;
+  // fields that are defined in the header file can just be used like normal variables here
+  cout << "- manufacturer: " << manufacturer << endl;
+  cout << "- model: " << model << endl;
+}
+
+car::car(string manufacturer, string model) {
+  // set manufacturer of the current object to the given manufacturer
+  this->manufacturer = manufacturer;
+  // set model of the current object to the given model
+  this->model = model;
+}

cpp/constructors/car.h

@@ -0,0 +1,22 @@
+#pragma once
+
+// including a necessary library and namespace to work with strings
+#include <string>
+using namespace std;
+
+// define the class
+class car
+{
+  private:
+    // define two fields, manufacturer and model
+    // this time as private to make the data only settable through the constructor or other local functions
+    std::string manufacturer;
+    std::string model;
+
+  public:
+    // define the constructor, taking manufacturer and model as parameters
+    car(std::string manufacturer, std::string model);
+
+    // define a method that will print out information
+    void print_info();
+};

cpp/constructors/main.cpp

@@ -3,16 +3,11 @@
 
 int main() {
   // create a new car and store it in the variable 'a'
-  // in contrast to java, c++ does not need initialization with the 'new' keyword here.
-  car a;
-  // set some data for that car
-  a.manufacturer = "Benz";
-  a.model = "Velo";
+  // The constructor requires manufacturer and model to be specified.
+  car a("Benz", "Velo");
 
   // do the same for a second car
-  car b;
-  b.manufacturer = "Ford";
-  b.model = "Model T";
+  car b("Ford", "Model T");
 
   // use a function of the car class to print out the information
   a.print_info();

cpp/instances/README.md

@@ -1,11 +0,0 @@
-# C++ Example
-
-## Language Specific
-
-c++ is almost identical to java in this example. 
-The only difference here is that c++ doesn't require the object
-to be initialized with the keyword 'new'.
-
-Relevant Files:
-
-- [main.cpp](./main.cpp)

cpp/instances/car.cpp

@@ -1,20 +0,0 @@
-/*
-
-Basic Car class
-just here to make the demonstration in the main file possible
-explanation of the code here will be given in later lessons
-
-*/
-
-#include "car.h"
-#include <iostream>
-#include <string>
-
-using namespace std;
-
-void car::print_info()
-{
-  cout << "Car Information:" << endl;
-  cout << "- manufacturer: " << manufacturer << endl;
-  cout << "- model: " << model << endl;
-}

cpp/instances/car.h

@@ -1,20 +0,0 @@
-/*
-
-Basic Car class
-just here to make the demonstration in the main file possible
-explanation of the code here will be given in later lessons
-
-*/
-
-#pragma once
-#include <string>
-
-using namespace std;
-
-class car
-{
-  public:
-    std::string manufacturer;
-    std::string model;
-    void print_info();
-};

java/Instances.md

@@ -0,0 +1,5 @@
+# Java Example
+
+Relevant Files:
+
+- [main.java](./classes/main.java)

java/classes/Car.java

@@ -8,6 +8,7 @@ public class Car {
   public String model = "";
   public String manufacturer = "";
 
+  // create the method print_info()
   public void print_info() {
     System.out.println("Car Information:");
     /**

java/constructors/Car.java

@@ -0,0 +1,23 @@
+public class Car {
+
+  // define the fields as private to prevent outside classes from accessing them
+  // access restriction will be a topic in the next lesson
+  private String model = "";
+  private String manufacturer = "";
+
+  // define the constructor
+  // in java a constructor is basically a function without return type named exactly like the class
+  public Car(String manufacturer, String model) {
+    // set manufacturer of the current object to the given manufacturer
+    this.manufacturer = manufacturer;
+    // set model of the current object to the given model
+    this.model = model;
+  }
+
+  // create the method print_info()
+  public void print_info() {
+    System.out.println("Car Information:");
+    System.out.println("- manufacturer: " + this.manufacturer);
+    System.out.println("- model: " + this.model);
+  }
+}

java/constructors/README.md

@@ -0,0 +1,6 @@
+# Java example
+
+Relevant files:
+
+- [main.java](./main.java)
+- [Car.java](./Car.java)

java/constructors/main.java

@@ -1,15 +1,11 @@
 public class main {
   public static void main(String[] args) {
     // create a new car and store it in the variable 'a'
-    Car a = new Car();
-    // set some data for that car
-    a.manufacturer = "Benz";
-    a.model = "Velo";
+    // the constructor requires manufacturer and model to be specified
+    Car a = new Car("Benz", "Velo");
 
     // do the same for a second car
-    Car b = new Car();
-    b.manufacturer = "Ford";
-    b.model = "Model T";
+    Car b = new Car("Ford", "Model T");
 
     // use a function of the car class to print out the information
     a.print_info();

java/instances/Car.java

@@ -1,18 +0,0 @@
-/*
-
-Basic Car class
-just here to make the demonstration in the main file possible
-explanation of the code here will be given in later lessons
-
-*/
-
-public class Car {
-  public String model = "";
-  public String manufacturer = "";
-
-  public void print_info() {
-    System.out.println("Car Information:");
-    System.out.println("- manufacturer: " + this.manufacturer);
-    System.out.println("- model: " + this.model);
-  }
-}

java/instances/README.md

@@ -1,5 +0,0 @@
-# Java Example
-
-Relevant Files:
-
-- [main.java](./main.java)

lessons/Constructors.md

@@ -0,0 +1,14 @@
+# Constructors
+
+Constructors are a way to give data to an object right when it gets created. The
+object can also run functions on that data during construction.
+
+Constructors should only be used to initialize data which the object needs to
+function.
+
+## Code examples and language specific explanations
+
+- [Java](../java/constructors/README.md)
+- [Rust](../rust/Constructors.md)
+- [C++](../cpp/constructors/README.md)
+- [JavaScript (using TypeScript)](../typescript/constructors/README.md)

lessons/Instances.md

@@ -7,10 +7,10 @@ Objects are generally used to keep data logically grouped and also make it easy
 to perform actions on them without having to account for all the logic at the
 time of using those functions.
 
-As an example I have created a Car class. This is probably going to be the
-main class used in all further lessons, since it has a lot of room for more data
-and functions to add except for manufacturer, model and the function print_info
-in this example.
+As an example I have created a Car class. This is probably going to be the main
+class used in all further lessons, since it has a lot of room for more data and
+functions to add except for manufacturer, model and the function print_info in
+this example.
 
 ```java
 /*
@@ -47,7 +47,8 @@ a.print_info();
 b.print_info();
 ```
 
-The above example code together with the car class will create the following output:
+The above example code together with the car class will create the following
+output:
 
 ```text
 Car Information:
@@ -64,7 +65,7 @@ repository :)
 
 ## Examples
 
-- [Java](../java/instances/README.md)
-- [Rust](../rust/instances/README.md)
-- [C++](../cpp/instances/README.md)
-- [JavaScript (using TypeScript)](../typescript/instances/README.md)
+- [Java](../java/Instances.md)
+- [Rust](../rust/Instances.md)
+- [C++](../cpp/Instances.md)
+- [JavaScript (using TypeScript)](../typescript/Instances.md)

rust/Constructors.md

@@ -0,0 +1,14 @@
+# Constructors in rust
+
+Rust is a special case for constructors. The language itself is already
+different from most other languages in structure, especially for object oriented
+programming.
+
+Simply said, there are no constructors in rust. When you create an object, you
+have to initialize all data immediately and by yourself.
+
+You can look into the classes or instances examples to see how object
+construction is done in rust.
+
+- [main.rs](./classes/src/main.rs)
+- [car.rs](./classes/src/car.rs)

rust/Instances.md

@@ -3,8 +3,9 @@
 ## Language specific
 
 - Rust doesn't use the 'new' keyword
-- Classes in Rust require all attributes to be defined at all times, so you have to define all the data on creation.
+- Classes in Rust require all attributes to be defined at all times, so you have
+  to define all the data on creation.
 
 Relevant Files
 
-- [main.rs](./src/main.rs)
+- [main.rs](./classes/src/main.rs)

rust/instances/Cargo.lock

@@ -1,5 +0,0 @@
-# This file is automatically @generated by Cargo.
-# It is not intended for manual editing.
-[[package]]
-name = "rust-oop"
-version = "0.1.0"

rust/instances/Cargo.toml

@@ -1,9 +0,0 @@
-[package]
-name = "rust-oop"
-version = "0.1.0"
-authors = ["Timo Hocker <t-hocker@web.de>"]
-edition = "2018"
-
-# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
-
-[dependencies]

rust/instances/src/car.rs

@@ -1,24 +0,0 @@
-/* 
-
-Basic Car class
-just here to make the demonstration in the main file possible
-explanation of the code here will be given in later lessons
-
-*/
-
-pub trait Information {
-  fn print_info(&self);
-}
-
-pub struct Car {
-  pub manufacturer: String,
-  pub model: String
-}
-
-impl Information for Car {
-  fn print_info(&self) {
-    println!("Car Information:");
-    println!("- manufacturer: {}", self.manufacturer);
-    println!("- model: {}", self.model);
-  }
-}

rust/instances/src/main.rs

@@ -1,23 +0,0 @@
-mod car;
-use car::Information;
-
-fn main() {
-  // create a new car and store it in the variable 'a'
-  // rust also doesn't use the 'new' keyword
-  // all attributes have to be defined upon creation of the object
-  let a = car::Car {
-    // set some data for that car
-    manufacturer: "Benz".to_string(),
-    model: "Velo".to_string()
-  };
-
-  // do the same for a second car
-  let b = car::Car {
-    manufacturer: "Ford".to_string(),
-    model: "Model T".to_string()
-  };
-
-  // use a function of the car class to print out the information
-  a.print_info();
-  b.print_info();
-}

typescript/Instances.md

@@ -0,0 +1,5 @@
+# Typescript Example
+
+Relevant Files
+
+- [index.ts](./classes/index.ts)

typescript/classes/car.ts

@@ -6,7 +6,7 @@ export class Car {
   manufacturer: string = '';
   model: string = '';
 
-  // define the function print_info
+  // define the method print_info
   print_info() {
     console.log('Car Information:');
     console.log(`- manufacturer: ${this.manufacturer}`);

typescript/constructors/README.md

@@ -1,5 +1,6 @@
 # Typescript Example
 
-Relevant Files
+## Relevant Files
 
 - [index.ts](./index.ts)
+- [car.ts](./car.ts)

typescript/constructors/car.ts

@@ -0,0 +1,23 @@
+/**
+ * the class is defined with the export keyword to make it usable outside of the current file
+ */
+export class Car {
+  // define the fields
+  // setting them to private to prevent access from outside
+  private manufacturer: string = '';
+  private model: string = '';
+
+  // in typescript constructors are defined with the keyword constructor
+  public constructor(manufacturer: string, model: string) {
+    // set manufacturer and model of the current object to the given parameters
+    this.manufacturer = manufacturer;
+    this.model = model;
+  }
+
+  // define the method print_info
+  print_info() {
+    console.log('Car Information:');
+    console.log(`- manufacturer: ${this.manufacturer}`);
+    console.log(`- model: ${this.model}`);
+  }
+}

typescript/constructors/index.ts

@@ -1,15 +1,11 @@
 import {Car} from './car'
 
 // create a new car and store it in the variable 'a'
-const a = new Car();
-// set some data for that car
-a.manufacturer = 'Benz';
-a.model = 'Velo';
+// the constructor requires the parameters for model and manufacturer
+const a = new Car('Benz','Velo');
 
 // do the same for a second car
-const b = new Car();
-b.manufacturer = 'Ford';
-b.model = 'Model T';
+const b = new Car('Ford','Model T');
 
 // use a function of the car class to print out the information
 a.print_info();

typescript/instances/car.ts

@@ -1,18 +0,0 @@
-/* 
-
-Basic Car class
-just here to make the demonstration in the main file possible
-explanation of the code here will be given in later lessons
-
-*/
-
-export class Car {
-  manufacturer: string = '';
-  model: string = '';
-
-  print_info() {
-    console.log('Car Information:');
-    console.log(`- manufacturer: ${this.manufacturer}`);
-    console.log(`- model: ${this.model}`);
-  }
-}