Tutorial by Examples | RIP Tutorial

Prepared statements in MySQLi

Please read Preventing SQL injection with Parametrized Queries for a complete discussion of why prepared statements help you secure your SQL statements from SQL Injection attacks The $conn variable here is a MySQLi object. See MySQLi connect example for more details. For both examples, we assume t...

PHP • PHP MySQLi

Getting the Constants of an Enumeration

Giving this enumeration as Example: enum Compass { NORTH(0), EAST(90), SOUTH(180), WEST(270); private int degree; Compass(int deg){ degree = deg; } public int getDegree(){ return degree; } } In Java an enum class is like any other c...

Java Language • Reflection API

Gauss's sum: 1 + 2 + 3 + ... + n

The sum 1 + 2 + 3 + ... + n Simplifies to n(n+1) / 2. Notice that this quantity is Θ(n2). This shortcut arises frequently in the analysis of algorithms like insertion sort or selection sort. Numbers of the form n(n+1)/2 are called the triangular numbers.

math • Common summations in computer science

Sums of Powers of Two: 1 + 2 + 4 + 8 + 16 + ...

The sum 20 + 21 + 22 + ... + 2n-1 simplifies to 2n - 1. This explains why the maximum value that can be stored in an unsigned 32-bit integer is 232 - 1.

math • Common summations in computer science

Sum of a geometric series: r^0 + r^1 + r^2 + ...

The sum of the geometric series r0 + r1 + r2 + ... + rn-1 In the case where r ≠ 1, simplifies to (rn - 1) / (r - 1). If r < 1, this sum is bounded from above by 1 / (1 - r). If r = 1, this sum is rn.

math • Common summations in computer science

Adding a spinner to your activity

In /res/values/strings.xml: <string-array name="spinner_options"> <item>Option 1</item> <item>Option 2</item> <item>Option 3</item> </string-array> In layout XML: <Spinner android:id="@+id/spinnerName" ...

Android • Spinner

Installation

Direct Download - download link CDN - get here Bower - bower install bootstrap [read] NPM - npm install bootstrap [read] Composer - composer require twbs/bootstrap [read] Customize - I you have your own config, you can customize here. Sass - For Sass related projects you may get it here. ...

twitter-bootstrap-3 • Getting started with twitter-bootstrap-3

Referring to the declared generic type within its own declaration

How do you go about using an instance of a (possibly further) inherited generic type within a method declaration in the generic type itself being declared? This is one of the problems you will face when you dig a bit deeper into generics, but still a fairly common one. Assume we have a DataSeries&l...

Java Language • Generics

basic model fitting

apologies: since I don't know of a channel for discussing/providing feedback on requests for improvement, I'm going to put my question here. Please feel free to point out a better place for this! @DataTx states that this is "completely unclear, incomplete, or has severe formatting problems&quot...

R Language • Hierarchical Linear Modeling

Basics of texturing

A texture is a form of data storage that allows convenient access not just to particular data entries, but also to sample points mixing (interpolating) multiple entries together. In OpenGL textures can be used for many things, but most commonly it's mapping an image to a polygon (for example a tria...

opengl • Texturing

Enabling Hibernate Caching in WildFly

To enable Second Level Caching for Hibernate in WildFly, add this property to your persistence.xml file: <property name="hibernate.cache.use_second_level_cache" value="true"/> You may also enable Query Caching with this property: <property name="hibernate.cache...

hibernate • Caching

Change primary key and timestamps

By default, Eloquent models expect for the primary key to be named 'id'. If that is not your case, you can change the name of your primary key by specifying the $primaryKey property. class Citizen extends Model { protected $primaryKey = 'socialSecurityNo'; // ... } Now, any Eloqu...

Laravel • Eloquent

Update an existing model

$user = User::find(1); $user->name = 'abc'; $user->save(); You can also update multiple attributes at once using update, which does not require using save afterwards: $user = User::find(1); $user->update(['name' => 'abc', 'location' => 'xyz']); You can also update a model(s)...

Laravel • Eloquent: Model

Throw 404 if entity not found

If you want to automatically throw an exception when searching for a record that isn't found on a modal, you can use either Vehicle::findOrFail(1); or Vehicle::where('make', 'ford')->firstOrFail(); If a record with the primary key of 1 is not found, a ModelNotFoundException is thrown. W...

Laravel • Eloquent

Reading and writing DataObjects

DataObjects in SilverStripe represent a database table row. The fields in the model have magic methods that handle getting and setting data via their property names. Given we have a simple DataObject as an example: class Fruit extends DataObject { private static $db = ['Name' => 'Varchar'...

silverstripe • Using the ORM

A View Bound to Existing HTML

Assuming this HTML in the page: <body> <div id="myPage"> </div> </body> A view can be bound to it with: var MyPageView = Backbone.View.extend( { "el": "#myPage", "template": _.template( "<p>This is m...

backbone.js • View

View's initialize function

initialize is called by Backbone right after a View is constructed. Optional parameters The initialize function receives any arguments passed to the view's constructor. Commonly, the options hash that is used to pass the view's default options: ['model', 'collection', 'el', 'id', 'attributes', 'c...

backbone.js • View

Closing Streams

Most streams must be closed when you are done with them, otherwise you could introduce a memory leak or leave a file open. It is important that streams are closed even if an exception is thrown. Java SE 7 try(FileWriter fw = new FileWriter("outfilename"); BufferedWriter bw = new Buf...

Java Language • InputStreams and OutputStreams

Gem installation from github/filesystem

You can install a gem from github or filesystem. If the gem has been checked out from git or somehow already on the file system, you could install it using gem install --local path_to_gem/filename.gem Installing gem from github. Download the sources from github mkdir newgem cd newgem git clon...

Ruby Language • Gem Usage

Defining Variadic Functions

A Clojure function can be defined to take an arbitrary number of arguments, using the symbol & in its argument list. All remaining arguments are collected as a sequence. (defn sum [& args] (apply + args)) (defn sum-and-multiply [x & args] (* x (apply + args))) Calling: =&gt...

clojure • Functions