Tutorial by Examples: at

Lambdas and Execute-around Pattern

There are several good examples of using lambdas as a FunctionalInterface in simple scenarios. A fairly common use case that can be improved by lambdas is what is called the Execute-Around pattern. In this pattern, you have a set of standard setup/teardown code that is needed for multiple scenarios ...

Java Language • Lambda Expressions

Attached dependency properties

When to use An attached property is a dependency property that can be applied to any DependencyObject to enhance the behavior of various controls or services that are aware of the property's existence. Some use cases for attached properties include: Having a parent element iterate through its c...

wpf • Dependency Properties

Getting file information

Check if a path is a directory or a file The is_dir function returns whether the argument is a directory, while is_file returns whether the argument is a file. Use file_exists to check if it is either. $dir = "/this/is/a/directory"; $file = "/this/is/a/file.txt"; echo is_d...

PHP • File handling

Creating Objects

Unlike many other languages, Perl does not have constructors that allocate memory for your objects. Instead, one should write a class method that both create a data structure and populate it with data (you may know it as the Factory Method design pattern). package Point; use strict; sub new { ...

Perl Language • Object-oriented Perl

Repeating Annotations

Until Java 8, two instances of the same annotation could not be applied to a single element. The standard workaround was to use a container annotation holding an array of some other annotation: // Author.java @Retention(RetentionPolicy.RUNTIME) public @interface Author { String value(); } ...

Java Language • Annotations

Create composite index

This will create a composite index of both keys, mystring and mydatetime and speed up queries with both columns in the WHERE clause. CREATE INDEX idx_mycol_myothercol ON my_table(mycol, myothercol) Note: The order is important! If the search query does not include both columns in the WHERE claus...

MySQL • Indexes and Keys

The onBackpressureXXX operators

Most developers encounter backpressure when their application fails with MissingBackpressureException and the exception usually points to the observeOn operator. The actual cause is usually the non-backpressured use of PublishSubject, timer() or interval() or custom operators created via create(). ...

rx-java • Backpressure

Using a base template

base.twig.html <!DOCTYPE html> <html> <head> <title>{{ title | default('Hello World') }}</title> <link rel="stylesheet" type="text/css" href="theme.css"> {% block css %} {% endblock %} &...

twig • Template inheritance

Change the content of an included template

article.twig.html <article> <h1>{{ article.title }}</h1> {% block content %} <p>{{ article.content }}</p> {% endblock %} </article> articles.twig.html {# use default template for article #} {% for article in articles %} {% include &...

twig • Template inheritance

Monkey Patching

In this case, "monkey patching" means adding a new variable or method to a class after it's been defined. For instance, say we defined class A as class A(object): def __init__(self, num): self.num = num def __add__(self, other): return A(self.num + other.num)...

Python Language • Classes

Efficient pixel access using cv::Mat::ptr pointer

If efficiency is important, a fast way to iterate over pixels in a cv::Mat object is to use its ptr<T>(int r) method to obtain a pointer to the beginning of row r (0-based index). According to the matrix type, the pointer will have a different template. For CV_8UC1: uchar* ptr = image.ptr&...

opencv • Pixel Access

Private key is not accepted (OpenSSH clients debug)

By default, most of the information is hidden from the user. You can use -v switches to get a verbose log of the connection attempt, which will usually pinpoint the problem by showing why the behavior is different than you expect. Let's assume you are connecting to the server example.com using ssh ...

Secure Shell • Debugging ssh problems

Skipping then taking some results (Pagination)

ISO/ANSI SQL: SELECT Id, Col1 FROM TableName ORDER BY Id OFFSET 20 ROWS FETCH NEXT 20 ROWS ONLY; MySQL: SELECT * FROM TableName LIMIT 20, 20; -- offset, limit Oracle; SQL Server: SELECT Id, Col1 FROM (SELECT Id, Col1, row_number() over (order by Id) RowNumbe...

SQL • SKIP TAKE (Pagination)

Removing the Admin Toolbar from all except Administrators

Add the following code to functions.php to remove it from everyone except the Administrator user level: add_action('after_setup_theme', 'no_admin_bar'); function no_admin_bar() { if (!current_user_can('administrator') && !is_admin()) { show_admin_bar(false); ...

WordPress • The Admin Bar (aka "The Toolbar")

Creating DTOs (POJOs/POCOs)

Data classes in kotlin are classes created to do nothing but hold data. Such classes are marked as data: data class User(var firstname: String, var lastname: String, var age: Int) The code above creates a User class with the following automatically generated: Getters and Setters for all prope...

Kotlin • Idioms

Dispatching Clack requests

Because a clack request is represented as a plist, we can use pattern matching as the entry point to the clack app as a way to route request to their appropriate controllers (defvar *app* (lambda (env) (match env ((plist :request-method :get :request-uri uri) (...

common-lisp • Pattern matching

defun-match

Using pattern matching one can intertwine function definition and pattern matching, similar to SML. (trivia:defun-match fib (index) "Return the corresponding term for INDEX." (0 1) (1 1) (index (+ (fib (1- index)) (fib (- index 2))))) (fib 5) ;; => 8

common-lisp • Pattern matching

Create a new Rails app with a non-standard database adapter

Rails is shipped by default with ActiveRecord, an ORM (Object Relational Mapping) derived from the pattern with the same name. As an ORM, it is built to handle relational-mapping, and more precisely by handling SQL requests for you, hence the limitation to SQL databases only. However, you can stil...

Ruby on Rails • Getting started with Ruby on Rails

Switch statement with case

With the case statement you can match values against one variable. The argument passed to case is expanded and try to match against each patterns. If a match is found, the commands upto ;; are executed. case "$BASH_VERSION" in [34]*) echo {1..4} ;; *) seq -s" ...

Bash • Control Structures

Installation

Introduction JetBrains PhpStorm is a commercial, cross-platform IDE for PHP. It is built on JetBrains' IntelliJ IDEA platform, which is written in Java. It will thus run on all major operating systems that support Java. Users can extend the IDE by installing plugins created for the IntelliJ Platfo...

phpstorm • Getting started with phpstorm