Tutorial by Examples: w

RecyclerView Basics

This is an example of using Android Support Library V7 RecyclerView. Support libraries are generally recommended because they provide backward-compatible versions of new features, provide useful UI elements that are not included in the framework, and provide a range of utilities that apps can draw o...

Xamarin.Android • RecyclerView

Profiling with XHProf

XHProf is a PHP profiler originally written by Facebook, to provide a more lightweight alternative to XDebug. After installing the xhprof PHP module, profiling can be enabled / disabled from PHP code: xhprof_enable(); doSlowOperation(); $profile_data = xhprof_disable(); The returned array wil...

PHP • Performance

When to use Currying

Currying is the technique of translating the evaluation of a function that takes multiple arguments into evaluating a sequence of functions, each with a single argument. This is normally useful when for example: different arguments of a function are calculated at different times. (Example 1) di...

Scala Language • Currying

Typical workflow of a neural network

The typical workflow of training and using neural networks, regardless of the library used, goes like this: Training Data Getting the training data: the X variable is the input, and the Y variable is the output. The simplest thing to do is to learn a logic gate, where X is a vector or two number...

neural-network • Getting started with neural-network

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

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

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

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

Overview

In Vue.js, conditional rendering is achieved by using a set of directives on elements in the template. v-if Element displays normally when condition is true. When the condition is false, only partial compilation occurs and the element isn't rendered into the DOM until the condition becomes true. ...

Vue.js • Conditional Rendering

v-show

The use of the v-show directive is almost identical to that of v-if. The only differences are that v-show does not support the <template> syntax, and there is no "alternative" condition. var vm = new Vue({ el: '#example', data: { a: true } }); The basic u...

Vue.js • Conditional Rendering

Shutdown NGINX

Run as a root user. Fast shutdown: nginx -s stop Graceful shutdown: nginx -s quit

nginx • Getting started with nginx

AES encryption of data using password in a secure way

The following example encrypts a given data block using AES. The encryption key is derived in a secure way (random salt, 1000 rounds of SHA-256). The encryption uses AES in CBC mode with random IV. Note that the data stored in the class EncryptedData (salt, iv, and encryptedData) can be concatenate...

Android • Data Encryption/Decryption

Filter items inside RecyclerView with a SearchView

add filter method in RecyclerView.Adapter: public void filter(String text) { if(text.isEmpty()){ items.clear(); items.addAll(itemsCopy); } else{ ArrayList<PhoneBookItem> result = new ArrayList<>(); text = text.toLower...

Android • RecyclerView

Provisioning remote machines with Ansible

We can provision remote systems with Ansible. You should have an SSH key-pair and you should take your SSH public key to the machine ~/.ssh/authorized_keys file. The porpuse is you can login without any authorization. Prerequisites: Ansible You need an Inventory file (for ex.: development.ini...

ansible • Getting started with ansible

Using an httpHandler (.ashx) to download a file from a specific location

Create a new httpHandler inside your ASP.NET project. Apply the following code (VB) to the handler file: Public Class AttachmentDownload Implements System.Web.IHttpHandler Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest ' pass an ID thr...

ASP.NET • httpHandlers

Using redux-thunk with jQuery.ajax

const loadUser = userId => dispatch => { dispatch({ type: 'USER_LOADING' }); $.ajax('/users/' + userId, { type: 'GET', dataType : 'json' }).done(response => { dispatch({ type: 'USER_LOADED', user: response }); }).fail((xhr, status, error) =>...

redux • Asynchronous Data Flow

Using the Controller with ControllerAs Syntax

The Controller we have made can be instantiated and used using controller as Syntax. That's because we have put variable directly on the controller class and not on the $scope. Using controller as someName is to seperate the controller from $scope itself.So, there is no need of injecting $scope as ...

AngularJS • Using AngularJS with TypeScript