Tutorial by Examples: g

Calling a method

assert ['cat', 'dog', 'fish']*.length() == [3, 3, 4] Note that when mixing types in the collection if the method not exists on some of the elements, a groovy.lang.MissingMethodException could be thrown: ['cat', 'dog', 'fish',3]*.length() // it throws groovy.lang.MissingMethodException: No sign...

groovy • Spread Operator

Accessing a property

class Vector { double x double y } def points = [ new Vector(x: 10, y: -5), new Vector(x: -17.5, y: 3), new Vector(x: -3.3, y: -1) ] assert points*.x == [10, -17.5, -3.3] Note: The * is optional. We could also write the above statement as in the below line and Groov...

groovy • Spread Operator

Spawning a shell to execute a command

To run a command in a shell, in which you required buffered output (i.e. it is not a stream), use child_process.exec. For example, if you wanted to run the command cat *.js file | wc -l, with no options, that would look like this: const exec = require('child_process').exec; exec('cat *.js file | w...

Node.js • Executing files or commands with Child Processes

Spawning a process to run an executable

If you are looking to run a file, such as an executable, use child_process.execFile. Instead of spawning a shell like child_process.exec would, it will directly create a new process, which is slightly more efficient than running a command. The function can be used like so: const execFile = require(...

Node.js • Executing files or commands with Child Processes

Testing Exceptions

Programs throw errors when for instance wrong input is given. Because of this, one needs to make sure that an error is thrown when actual wrong input is given. Because of that we need to check for an exact exception, for this example we will use the following exception: class WrongInputException(Ex...

Python Language • Unit Testing

Invalidating the module cache

In development, you may find that using require() on the same module multiple times always returns the same module, even if you have made changes to that file. This is because modules are cached the first time they are loaded, and any subsequent module loads will load from the cache. To get around ...

Node.js • Exporting and Consuming Modules

Using ManyToMany Fields

We use this model from the first example: class Person(models.Model): name = models.CharField(max_length=50) description = models.TextField() class Club(models.Model): name = models.CharField(max_length=50) members = models.ManyToManyField(Person) Add Tom and Bill to the N...

Django • Many-to-many relationships

Looping over iterables

You can loop over any iterable by using the standard for-loop: val list = listOf("Hello", "World", "!") for(str in list) { print(str) } Lots of things in Kotlin are iterable, like number ranges: for(i in 0..9) { print(i) } If you need an index while...

Kotlin • Loops in Kotlin

Strategy

A strategy pattern can be used in Javascript in many cases to replace a switch statement. It is especially helpful when the number of conditions is dynamic or very large. It allows the code for each condition to be independent and separately testable. Strategy object is simple an object with multip...

JavaScript • Conditions

Using Elements from the Polymer Catalog

Polymer prodives a lot of well built elements for you to use in your app. Browse them in their Element Catalog. Let's go through the workflow of using an element by including paper-input (Documentation) Download the Element To Download an element there are two ways: Bower The convinient way is...

polymer • Getting started with polymer

Example showcasing the basic concepts

The following example is an introduction to: Template compilation using underscore Accessing variables in a template Creating a view Rendering a view Showing a view <html> <head> <script src="https://code.jquery.com/jquery-3.1.0.min.js"></script> ...

backbone.js • Getting started with backbone.js

Creating a Dialog with Tabbed Titlebar

Occasionally, we may want to display dialogs with more than one pane of content. jQuery UI offers tabs that can be used in tandem with a dialog to make this possible. While it may be more common to have tabs within a dialog's content container, this example will demonstrate how to make a list of t...

jQuery UI Library • Dialog

Generic algorithms

Higher-order functions can be used to implement generic algorithms, giving up the responsibility of providing final details to the user. For instance List.sort expects a comparison function, which allows to implement various ways of sorting. Here we implement case-insensitive sorting of strings: le...

OCaml • Higher Order Functions

Changing default shell

Most modern distributions will come with BASH (Bourne Again SHell) pre-installed and configured as a default shell. The command (actually an executable binary, an ELF) that is responsible for changing shells in Linux is chsh (change shell). We can first check which shells are already installed and...

GNU/Linux • Shell

Get CSS property

To get an element's CSS property you can use the .css(propertyName) method: var color = $('#element').css('color'); var fontSize = $('#element').css('font-size');

jQuery • CSS Manipulation

Unit testing using Theories

From JavaDoc The Theories runner allows to test a certain functionality against a subset of an infinite set of data points. Running theories import org.junit.experimental.theories.Theories; import org.junit.experimental.theories.Theory; import org.junit.runner.RunWith; @RunWith(Theories...

junit • Tests

Creating basic deadlocked system

A deadlock occurs when two competing actions wait for the other to finish, and thus neither ever does. In java there is one lock associated with each object. To avoid concurrent modification done by multiple threads on single object we can use synchronized keyword, but everything comes at a cost....

Java Language • Concurrent Programming (Threads)