Tutorial by Examples: n

Setting constraints programmatically

Boilerplate code example override func viewDidLoad() { super.viewDidLoad() let myView = UIView() myView.backgroundColor = UIColor.blueColor() myView.translatesAutoresizingMaskIntoConstraints = false view.addSubview(myView) // Add constraints code here // ... ...

iOS • Auto Layout

Center Constraints

Select your button (or whatever view you want to center) on the storyboard. Then click the align button on the bottom right. Select Horizontally in Container and Vertically in Container. Click "Add 2 Constraints". If it wasn't perfectly centered already, you may need to do one more thin...

iOS • Auto Layout

Range and addition

Let's take an example of adding a value to a range (as it could be done in a loop for example): 3+1:5 Gives: [1] 4 5 6 7 8 This is because the range operator : has higher precedence than addition operator +. What happens during evaluation is as follows: 3+1:5 3+c(1, 2, 3, 4, 5) expansio...

R Language • Arithmetic Operators

Installation

Laravel applications are installed and managed with Composer, a popular PHP dependency manager. There are two ways to create a new Laravel application. Via Composer $ composer create-project laravel/laravel [foldername] Or $ composer create-project --prefer-dist laravel/laravel [foldername] ...

Laravel • Installation

Basic table creation

The CREATE TABLE statement is used to create a table in a MySQL database. CREATE TABLE Person ( `PersonID` INTEGER NOT NULL PRIMARY KEY, `LastName` VARCHAR(80), `FirstName` VARCHAR(80), `Address` TEXT, `City` VARCHAR(100) ) Engine=InnoDB; Ev...

MySQL • Table Creation

Table creation with Primary Key

CREATE TABLE Person ( PersonID INT UNSIGNED NOT NULL, LastName VARCHAR(66) NOT NULL, FirstName VARCHAR(66), Address VARCHAR(255), City VARCHAR(66), PRIMARY KEY (PersonID) ); A primary key is a NOT NULL single or a multi-column identifier whic...

MySQL • Table Creation

Table creation with Foreign Key

CREATE TABLE Account ( AccountID INT UNSIGNED NOT NULL, AccountNo INT UNSIGNED NOT NULL, PersonID INT UNSIGNED, PRIMARY KEY (AccountID), FOREIGN KEY (PersonID) REFERENCES Person (PersonID) ) ENGINE=InnoDB; Foreign key: A Foreign Key (FK) is either a single col...

MySQL • Table Creation

Installation or Setup

Detailed instructions on getting pandas set up or installed can be found here in the official documentation. Installing pandas with Anaconda Installing pandas and the rest of the NumPy and SciPy stack can be a little difficult for inexperienced users. The simplest way to install not only pandas, ...

pandas • Getting started with pandas

Number

5 <input type="number" value="0" name="quantity"> The Input element with a type attribute whose value is number represents a precise control for setting the element’s value to a string representing a number. Please note that this field does not guarantee to h...

HTML • Input Control Elements

Installation or Setup

ReactJS is a JavaScript library contained in a single file react-<version>.js that can be included in any HTML page. People also commonly install the React DOM library react-dom-<version>.js along with the main React file: Basic Inclusion <!DOCTYPE html> <html> <...

React • Getting started with React

Create an XML file using XMLWriter

Instantiate a XMLWriter object: $xml = new XMLWriter(); Next open the file to which you want to write. For example, to write to /var/www/example.com/xml/output.xml, use: $xml->openUri('file:///var/www/example.com/xml/output.xml'); To start the document (create the XML open tag): $xml-&gt...

PHP • XML

Show both staged and unstaged changes

To show all staged and unstaged changes, use: git diff HEAD NOTE: You can also use the following command: git status -vv The difference being that the output of the latter will actually tell you which changes are staged for commit and which are not.

Git • Git Diff

Installation or Setup

Knockout is available on most JavaScript platforms, or as a standalone script. Include as a script You can download the script from it's download page, then include it in your page with a standard script tag <script type='text/javascript' src='knockout-3.4.0.js'></script> Using a C...

knockout.js • Getting started with knockout.js

Clearing an activity stack

Sometimes you may want to start a new activity while removing previous activities from the back stack, so the back button doesn't take you back to them. One example of this might be starting an app on the Login activity, taking you through to the Main activity of your application, but on logging out...

Android • Intent

Linear regression on the mtcars dataset

The built-in mtcars data frame contains information about 32 cars, including their weight, fuel efficiency (in miles-per-gallon), speed, etc. (To find out more about the dataset, use help(mtcars)). If we are interested in the relationship between fuel efficiency (mpg) and weight (wt) we may start p...

R Language • Linear Models (Regression)

Use anonymous functions with apply

apply is used to evaluate a function (maybe an anonymous one) over the margins of an array or matrix. Let's use the iris dataset to illustrate this idea. The iris dataset has measurements of 150 flowers from 3 species. Let's see how this dataset is structured: > head(iris) Sepal.Length Sep...

R Language • *apply family of functions (functionals)

Cloning an existing table

A table can be replicated as follows: CREATE TABLE ClonedPersons LIKE Persons; The new table will have exactly the same structure as the original table, including indexes and column attributes. As well as manually creating a table, it is also possible to create table by selecting data from anot...

MySQL • Table Creation

Array definition

Dim array(9) As Integer ' Defines an array variable with 10 Integer elements (0-9). Dim array = New Integer(10) {} ' Defines an array variable with 11 Integer elements (0-10) 'using New. Dim array As Integer() = {1, 2, 3, 4} ' Defines an Integer array variable a...

Visual Basic .NET Language • Array

Enum Polymorphism Pattern

When a method need to accept an "extensible" set of enum values, the programmer can apply polymorphism like on a normal class by creating an interface which will be used anywere where the enums shall be used: public interface ExtensibleEnum { String name(); } This way, any enum t...

Java Language • Enums

Reversing Strings

2.2 let aString = "This is a test string." // first, reverse the String's characters let reversedCharacters = aString.characters.reverse() // then convert back to a String with the String() initializer let reversedString = String(reversedCharacters) print(reversedString) // &q...

Swift Language • Strings and Characters