Tutorial by Examples: u

Using Auto Increment

Many databases allow to make the primary key value automatically increment when a new key is added. This ensures that every key is different. MySQL CREATE TABLE Employees ( Id int NOT NULL AUTO_INCREMENT, PRIMARY KEY (Id) ); PostgreSQL CREATE TABLE Employees ( Id SERIAL PRIMARY...

SQL • Primary Keys

Virtual Inheritance

When using inheritance, you can specify the virtual keyword: struct A{}; struct B: public virtual A{}; When class B has virtual base A it means that A will reside in most derived class of inheritance tree, and thus that most derived class is also responsible for initializing that virtual base: ...

C++ • Classes/Structures

Multiple Inheritance

Aside from single inheritance: class A {}; class B : public A {}; You can also have multiple inheritance: class A {}; class B {}; class C : public A, public B {}; C will now have inherit from A and B at the same time. Note: this can lead to ambiguity if the same names are used in multipl...

C++ • Classes/Structures

What is Function Overloading?

Function overloading is having multiple functions declared in the same scope with the exact same name exist in the same place (known as scope) differing only in their signature, meaning the arguments they accept. Suppose you are writing a series of functions for generalized printing capabilities, b...

C++ • Function Overloading

Using std::vector as a C array

There are several ways to use a std::vector as a C array (for example, for compatibility with C libraries). This is possible because the elements in a vector are stored contiguously. C++11 std::vector<int> v{ 1, 2, 3 }; int* p = v.data(); In contrast to solutions based on previous C++ st...

C++ • std::vector

Manipulating element classes

Assuming the page includes an HTML element like: This is a small <a href="https://en.wikipedia.org/wiki/Paragraph">paragraph</a> with a <a class="trusted" href="http://stackexchange.com">link</a>...

jQuery • DOM Manipulation

Adding the jQuery UI script & basic usage

To get started with the jQuery UI library, you'll need to add the jQuery script, the jQuery UI script, and the jQuery UI stylesheet to your HTML. First, download jQuery UI; choose the features you need on the download page. Unzip your download, and put jquery-ui.css and jquery-ui.js (and jquery.js)...

jQuery UI Library • Getting started with jQuery UI Library

Selecting elements using CSS selectors

String html = "<!DOCTYPE html>" + "<html>" + "<head>" + "<title>Hello world!</title>" + "</head>" + "<body>" + ...

Jsoup • Selectors

Number of Lines

When you make a label and set its text to be more than a single line that it can display, it will be truncated and you will see only one line of text ending with three dots (...). This is because a property called numberOfLines is set to 1, and therefore only one line will be displayed. It is a comm...

iOS • UILabel

Creating a UIButton

UIButtons can be initialized in a frame: Swift let button = UIButton(frame: CGRect(x: x, y: y, width: width, height: height) Objective C UIButton *button = [[UIButton alloc] initWithFrame:CGRectMake(x, y, width, height)]; A specific type of UIButton can be created like this: Swift let but...

iOS • UIButton

Using the `HTTP[S]_PROXY` env var

This page describes how to use the Meteor command-line tool (for example, when downloading packages, deploying your app, etc) behind a proxy server. Like a lot of other command-line software, the Meteor tool reads the proxy configuration from the HTTP_PROXY and HTTPS_PROXY environment variables (th...

meteor • Using Meteor with a Proxy Server

Using PuTTY (Advanced)

If you don't want to add Unix commands to your PATH on Windows, you can download a standalone SSH client like PuTTY. Download PuTTY here, then follow the instructions below to get a build machine. Call meteor admin get-machine <os-architecture> --json Copy and save the private key from the...

meteor • Accessing Meteor build machines from Windows

Using Cygwin (Unix tools on Windows)

The easiest way to get up and running is to install Git for Windows from this download page, and select "Use Git and optional Unix tools from the Windows Command Prompt" as in the screenshot below. After this, meteor admin get-machine <os-architecture> will work exactly as it does...

meteor • Accessing Meteor build machines from Windows

Getting the screen resolution

To get the physical size of the screen (including window chrome and menubar/launcher): var width = window.screen.width, height = window.screen.height;

JavaScript • Screen

Getting color information about the screen

To determine the color and pixel depths of the screen: var pixelDepth = window.screen.pixelDepth, colorDepth = window.screen.colorDepth;

JavaScript • Screen

Bold, Italic, and Underline

Bold Text To bold text, use the or tags: Bold Text Here or Bold Text Here What’s the difference? Semantics. is used to indicate that the text is fundamentally or semantically important to the surrounding...

HTML • Text Formatting

Superscript and Subscript

To offset text either upward or downward you can use the tags and . To create superscript: superscript here To create subscript: subscript here

HTML • Text Formatting

Constructing collections from existing data

Standard Collections Java Collections framework A simple way to construct a List from individual data values is to use java.utils.Arrays method Arrays.asList: List<String> data = Arrays.asList("ab", "bc", "cd", "ab", "bc", "cd"); ...

Java Language • Collections

Determine if an existing password hash can be upgraded to a stronger algorithm

If you are using the PASSWORD_DEFAULT method to let the system choose the best algorithm to hash your passwords with, as the default increases in strength you may wish to rehash old passwords as users log in <?php // first determine if a supplied password is valid if (password_verify($plaintex...

PHP • Password Hashing Functions

Structs are value types

Unlike classes, which are passed by reference, structures are passed through copying: first = "Hello" second = first first += " World!" // first == "Hello World!" // second == "Hello" String is a structure, therefore it's copied on assignment. Structu...

Swift Language • Structs