Tutorial by Examples: al

Installation or Setup

Detailed instructions on getting webdriver set up or installed.

webdriver • Getting started with webdriver

Send a single message using an alphanumeric sender id

An HTTP POST request is sent to a URL of the format: "https://api.twilio.com/2xxx-xx-xx/Accounts/[AccountSid]/Messages.json The example below uses a alphanumeric string as the sender. At the time of writing a sender ID can only be added through a service request Twlio. Example Request: To=&q...

Twilio • Send an SMS message using Bash and cURL

Checking if your app is already registered for Push Notification

Swift let isPushEnabled = UIApplication.sharedApplication().isRegisteredForRemoteNotifications()

iOS • Push Notifications

Installation or Setup

To install dplyr simply type in the R console. install.packages("dplyr") And then to load dplyr, type library("dplyr") It's also possible to install the latest development version from Github with: if (packageVersion("devtools") < 1.6) { install.packages...

dplyr • Getting started with dplyr

Installation or Setup

Python Windows The easiest way to install GTK3 for Python is by using PyGObject for Windows. It offers an installer that installs most things you need to develop GTK appilcations. The number of options the PyGObject installer offers can be daunting, but for most GTK projects the only option you h...

gtk3 • Getting started with gtk3

fatal error: ***: No such file or directory

The compiler can't find a file (a source file uses #include "someFile.hpp"). qmake: INCLUDEPATH += dir/Of/File cmake: include_directories(dir/Of/File) g++ call: g++ -o main main.cpp -Idir/Of/File

C++ • Common compile/linker errors (GCC)

Active Patterns can be used to validate and transform function arguments

An interesting but rather unknown usage of Active Patterns in F# is that they can be used to validate and transform function arguments. Consider the classic way to do argument validation: // val f : string option -> string option -> string let f v u = let v = defaultArg v "Hello&quo...

F# • Active Patterns

Checking end of file inside a loop condition, bad practice?

eof returns true only after reading the end of file. It does NOT indicate that the next read will be the end of stream. while (!f.eof()) { // Everything is OK f >> buffer; // What if *only* now the eof / fail bit is set? /* Use `buffer` */ } You could correctly write: ...

C++ • File I/O

Applying a Function to Every Value of an Array in Javascript

var numbers = [1,2,3,4,5]; var squares = numbers.map(function(x) { return x*x; }); // squares is [1,4,9,16,25]

arrays • Various ways of accessing arrays

Calculate Single Value from Array in Javascript

var arr = [1, 2, 3, 4, 5]; var sum = arr.reduce((prev, curr) => prev + curr); console.log(sum); // Output: 15 You can also specify an initial value var arr = [1, 2, 3, 4, 5]; var sum = arr.reduce(function (previousValue, currentValue, currentIndex, array) { return previousValue + cur...

arrays • Various ways of accessing arrays

Prevent sensitive methods from being called in templates

When an object is exposed to the template context, its arguments-less methods are available. This is useful when these functions are "getters". But it can be hazardeous if these methods alter some data or have some side effects. Eventhough you likely trust the template writer, he may not b...

Django • Templating

Installation or Setup

Chart.js can be included in several different ways: NPM Run the following command on your NPM project directory npm install chart.js --save CDN Include a script tag in your HTML linking to the chart.js CDN <html> <body> <script type="text/javascript" s...

chart.js • Getting started with chart.js

Using character constants instead of string literals, and vice versa

In C, character constants and string literals are different things. A character surrounded by single quotes like 'a' is a character constant. A character constant is an integer whose value is the character code that stands for the character. How to interpret character constants with multiple charac...

C Language • Common pitfalls

Flowing execution context with AsyncLocal

When you need to pass some data from the parent task to its children tasks, so it logically flows with the execution, use AsyncLocal class: void Main() { AsyncLocal<string> user = new AsyncLocal<string>(); user.Value = "initial user"; // this does not aff...

.NET Framework • Task Parallel Library (TPL)

Synchronous Get Call

private final OkHttpClient client = new OkHttpClient(); public void run() throws Exception { Request request = new Request.Builder() .url(yourUrl) .build(); Response response = client.newCall(request).execute(); if (!response.isSuccessful()) throw new IOExcept...

Android • OkHttp

Asynchronous Get Call

private final OkHttpClient client = new OkHttpClient(); public void run() throws Exception { Request request = new Request.Builder() .url(yourUrl) .build(); client.newCall(request).enqueue(new Callback() { @Override public void onFailure(Call call, IOExcepti...

Android • OkHttp

Installation or Setup

Detailed instructions on getting material-design set up or installed.

material-design • Getting started with material-design

Optimally fit elements to their container

One of the nicest features of flexbox is to allow optimally fitting containers to their parent element. Live demo. HTML: <div class="flex-container"> <div class="flex-item">1</div> <div class="flex-item">2</div> <div class=&q...

CSS • Flexible Box Layout (Flexbox)

Global and local AssemblyInfo

Having a global allows for better DRYness, you need only put values that are different into AssemblyInfo.cs for projects that have variance. This use assumes your product has more than one visual studio project. GlobalAssemblyInfo.cs using System.Reflection; using System.Runtime.InteropServices...

C# Language • AssemblyInfo.cs Examples

Conditional validation

Sometimes you may need to validate record only under certain conditions. class User < ApplicationRecord validates :name, presence: true, if: :admin? def admin? conditional here that returns boolean value end end If you conditional is really small, you can use a Proc: class ...

Ruby on Rails • ActiveRecord Validations