Tutorial by Examples: st

def say_hi MESSAGE = "Hello" puts MESSAGE end The above code results in an error: SyntaxError: (irb):2: dynamic constant assignment.

class Message DEFAULT_MESSAGE = "Hello, world" def speak(message = nil) if message puts message else puts DEFAULT_MESSAGE end end end The constant DEFAULT_MESSAGE can be changed with the following code: Message::DEFAULT_MESSAGE = "Hullo, wo...

Instance variables have an object wide scope, they can be declared anywhere in the object, however an instance variable declared on class level, will only be visible in the class object. A variable will be considered an instance variable when prefixed with @. Instance variables are used to set and g...

public void SaveNewEmployee(Employee newEmployee) { // best practice - wrap all database connections in a using block so they are always closed & disposed even in the event of an Exception // best practice - retrieve the connection string by name from the app.config or web.config (dep...

The easiest way to install and manage various versions of Ruby with rbenv is to use the ruby-build plugin. First clone the rbenv repository to your home directory: $ git clone https://github.com/rbenv/rbenv.git ~/.rbenv Then clone the ruby-build plugin: $ git clone https://github.com/rbenv/rub...

It is best to use latest SLIME from Emacs MELPA repository: the packages may be a bit unstable, but you get the latest features. Portale and multiplatform Emacs, Slime, Quicklisp, SBCL and Git You can download a portable and multiplatform version of Emacs25 already configured with Slime, SBCL, Qui...

In Emacs M-x slime will start slime with the default (first) Common Lisp implementation. If there are multiple implementations provided (via variable slime-lisp-implementations), other implementations can be accessed via M-- M-x slime, which will offer the choice of available implementations in mini...

C++17 namespace a { namespace b { template<class T> struct qualifies : std::false_type {}; } } namespace other { struct bob {}; } namespace a::b { template<> struct qualifies<::other::bob> : std::true_type {}; } You can enter both the a and b n...

Example: Invoke different constructors by passing relevant parameters import java.lang.reflect.*; class NewInstanceWithReflection{ public NewInstanceWithReflection(){ System.out.println("Default constructor"); } public NewInstanceWithReflection( String a){ ...

Minikube creates a local cluster of virtual machines to run Kubernetes on.It is the simplest method to get your hands dirty with Kubernetes on your local machine. Documentation for Minikube can be found at http://kubernetes.io/docs/getting-started-guides/minikube/ Requirements On macOS, xhyve ...

var baseType = typeof(List<>); var genericType = baseType.MakeGenericType(typeof(String)); var instance = Activator.CreateInstance(genericType); var method = genericType.GetMethod("GetHashCode"); var result = method.Invoke(instance, new object[] { });

If your enum class is required to have static fields, keep in mind they are created after the enum values themselves. That means, the following code will result in a NullPointerException: enum Example { ONE(1), TWO(2); static Map<String, Integer> integers = new HashMap<>(); ...

Compare two Strings ignoring case: "School".equalsIgnoreCase("school"); // true Don't use text1.toLowerCase().equals(text2.toLowerCase()); Languages have different rules for converting upper and lower case. A 'I' would be converted to 'i' in English. But in Turkish a 'I' ...

GWT ships with a command line utility called webAppCreator that automatically generates all the files you’ll need in order to start a GWT project. It also generates Eclipse project files and launch config files for easy debugging in GWT’s development mode. You can create a new demo application in a...

You should already have your backend REST resource available. On the client side (GWT) your need to Add RestyGwt dependency to your project with maven <dependency> <groupId>org.fusesource.restygwt</groupId> <artifactId>restygwt</artifactId> <vers...

import java.util.ArrayList; import java.util.List; import static java.lang.System.out; public class PolymorphismDemo { public static void main(String[] args) { List<FlyingMachine> machines = new ArrayList<FlyingMachine>(); machines.add(new FlyingMachine())...

This function copies data between two streams - void copy(InputStream in, OutputStream out) throws IOException { byte[] buffer = new byte[8192]; while ((bytesRead = in.read(buffer)) > 0) { out.write(buffer, 0, bytesRead); } } Example - // reading from System.in and ...

Let's say you have this line of code: printf("Hello, world!\n"); Now say you want to change the text to "Program exiting." CommandBufferMnemonicci"printf("¦");change in the ".Program exiting.\n<esc>printf("Program exiting.\n");

When we use a condition within another condition we say the conditions are "nested". One special case of nested conditions is given by the elseif option, but there are numerous other ways to use nested conditons. Let's examine the following code: a = 2; if mod(a,2)==0 % MOD - modulo o...

To check if a required gem is installed, from within your code, you can use the following (using nokogiri as an example): begin found_gem = Gem::Specification.find_by_name('nokogiri') require 'nokogiri' .... <the rest of your code> rescue Gem::LoadError end However, this can ...