constructors

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
 - encapsulation
 - getter / setter / property
 - inheritance
 - polymorphism
 - virtual classes
 - interfaces
+- Factories

cpp/constructors/README.md

@@ -0,0 +1,6 @@
+# Constructors in C++
+
+## Relevant files
+
+- [car.h](./car.h)
+- [car.cpp](./car.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

@@ -0,0 +1,15 @@
+#include "car.h"
+#include <cstring>
+
+int main() {
+  // create a new car and store it in the variable 'a'
+  // The constructor requires manufacturer and model to be specified.
+  car a("Benz", "Velo");
+
+  // do the same for a second car
+  car b("Ford", "Model T");
+
+  // use a function of the car class to print out the information
+  a.print_info();
+  b.print_info();
+}

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

@@ -0,0 +1,14 @@
+public class main {
+  public static void main(String[] args) {
+    // create a new car and store it in the variable 'a'
+    // 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("Ford", "Model T");
+
+    // use a function of the car class to print out the information
+    a.print_info();
+    b.print_info();
+  }
+}

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/README.md)
+- [C++](../cpp/constructors/README.md)
+- [JavaScript (using TypeScript)](../typescript/constructors/README.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)

typescript/constructors/README.md

@@ -0,0 +1,6 @@
+# Typescript Example
+
+## 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

@@ -0,0 +1,12 @@
+import {Car} from './car'
+
+// create a new car and store it in the variable 'a'
+// 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('Ford','Model T');
+
+// use a function of the car class to print out the information
+a.print_info();
+b.print_info();

typescript/constructors/package.json

@@ -0,0 +1,11 @@
+{
+  "name": "ts-oop",
+  "version": "1.0.0",
+  "description": "",
+  "main": "index.js",
+  "scripts": {
+    "test": "echo \"Error: no test specified\" && exit 1"
+  },
+  "author": "",
+  "license": "ISC"
+}

typescript/constructors/tsconfig.json

@@ -0,0 +1,66 @@
+{
+  "compilerOptions": {
+    /* Basic Options */
+    // "incremental": true,                   /* Enable incremental compilation */
+    "target": "es5",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019', 'ES2020', or 'ESNEXT'. */
+    "module": "commonjs",                     /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', 'es2020', or 'ESNext'. */
+    // "lib": [],                             /* Specify library files to be included in the compilation. */
+    // "allowJs": true,                       /* Allow javascript files to be compiled. */
+    // "checkJs": true,                       /* Report errors in .js files. */
+    // "jsx": "preserve",                     /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
+    // "declaration": true,                   /* Generates corresponding '.d.ts' file. */
+    // "declarationMap": true,                /* Generates a sourcemap for each corresponding '.d.ts' file. */
+    // "sourceMap": true,                     /* Generates corresponding '.map' file. */
+    // "outFile": "./dist",                       /* Concatenate and emit output to single file. */
+    "outDir": "./dist",                        /* Redirect output structure to the directory. */
+    // "rootDir": "./",                       /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
+    // "composite": true,                     /* Enable project compilation */
+    // "tsBuildInfoFile": "./",               /* Specify file to store incremental compilation information */
+    // "removeComments": true,                /* Do not emit comments to output. */
+    // "noEmit": true,                        /* Do not emit outputs. */
+    // "importHelpers": true,                 /* Import emit helpers from 'tslib'. */
+    // "downlevelIteration": true,            /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
+    // "isolatedModules": true,               /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */
+
+    /* Strict Type-Checking Options */
+    "strict": true,                           /* Enable all strict type-checking options. */
+    // "noImplicitAny": true,                 /* Raise error on expressions and declarations with an implied 'any' type. */
+    // "strictNullChecks": true,              /* Enable strict null checks. */
+    // "strictFunctionTypes": true,           /* Enable strict checking of function types. */
+    // "strictBindCallApply": true,           /* Enable strict 'bind', 'call', and 'apply' methods on functions. */
+    // "strictPropertyInitialization": true,  /* Enable strict checking of property initialization in classes. */
+    // "noImplicitThis": true,                /* Raise error on 'this' expressions with an implied 'any' type. */
+    // "alwaysStrict": true,                  /* Parse in strict mode and emit "use strict" for each source file. */
+
+    /* Additional Checks */
+    // "noUnusedLocals": true,                /* Report errors on unused locals. */
+    // "noUnusedParameters": true,            /* Report errors on unused parameters. */
+    // "noImplicitReturns": true,             /* Report error when not all code paths in function return a value. */
+    // "noFallthroughCasesInSwitch": true,    /* Report errors for fallthrough cases in switch statement. */
+
+    /* Module Resolution Options */
+    // "moduleResolution": "node",            /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
+    // "baseUrl": "./",                       /* Base directory to resolve non-absolute module names. */
+    // "paths": {},                           /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
+    // "rootDirs": [],                        /* List of root folders whose combined content represents the structure of the project at runtime. */
+    // "typeRoots": [],                       /* List of folders to include type definitions from. */
+    // "types": [],                           /* Type declaration files to be included in compilation. */
+    // "allowSyntheticDefaultImports": true,  /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */
+    "esModuleInterop": true,                  /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
+    // "preserveSymlinks": true,              /* Do not resolve the real path of symlinks. */
+    // "allowUmdGlobalAccess": true,          /* Allow accessing UMD globals from modules. */
+
+    /* Source Map Options */
+    // "sourceRoot": "",                      /* Specify the location where debugger should locate TypeScript files instead of source locations. */
+    // "mapRoot": "",                         /* Specify the location where debugger should locate map files instead of generated locations. */
+    // "inlineSourceMap": true,               /* Emit a single file with source maps instead of having a separate file. */
+    // "inlineSources": true,                 /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */
+
+    /* Experimental Options */
+    // "experimentalDecorators": true,        /* Enables experimental support for ES7 decorators. */
+    // "emitDecoratorMetadata": true,         /* Enables experimental support for emitting type metadata for decorators. */
+
+    /* Advanced Options */
+    "forceConsistentCasingInFileNames": true  /* Disallow inconsistently-cased references to the same file. */
+  }
+}