Tutorial by Examples: st

Remove an existing column from a table

To remove existing column name from users table, run the command: rails generate migration RemoveNameFromUsers name:string This will generate the following migration: class RemoveNameFromUsers < ActiveRecord::Migration[5.0] def change remove_column :users, :name, :string end end ...

Ruby on Rails • ActiveRecord Migrations

Adding multiple columns to a table

To add multiple columns to a table, separate field:type pairs with spaces when using rails generate migration command. The general syntax is: rails generate migration NAME [field[:type][:index] field[:type][:index]] [options] For example, the following will add name, salary and email fields to ...

Ruby on Rails • ActiveRecord Migrations

Case statement

Ruby uses the case keyword for switch statements. As per the Ruby Docs: Case statements consist of an optional condition, which is in the position of an argument to case, and zero or more when clauses. The first when clause to match the condition (or to evaluate to Boolean truth, if the condi...

Ruby Language • Control Flow

Installation or Setup

In short: XPages is part of IBM Domino Designer. Extra setup or installation isn't required for XPages. First XPage / Hello-World-Example To create your first XPage you have to create a new NSF first. Open the IBM Domino Designer, and open the menu "File" -> "New" -> &...

xpages • Getting started with xpages

Substitution Using Shell Variables

Variables inside single quotes ' don't get expanded by POSIX compatible shells, so using a shell variable in a sed substitution requires the use of double quotes " instead of single quotes ': $ var="he" $ echo "hello" | sed "s/$var/XX/" XXllo $ var="he&q...

sed • Substitution

Mutating a Struct

A method of a struct that change the value of the struct itself must be prefixed with the mutating keyword struct Counter { private var value = 0 mutating func next() { value += 1 } } When you can use mutating methods The mutating methods are only available on str...

Swift Language • Structs

Select rows that match a condition

Generally, the syntax is: SELECT <column names> FROM <table name> WHERE <condition> For example: SELECT FirstName, Age FROM Users WHERE LastName = 'Smith' Conditions can be complex: SELECT FirstName, Age FROM Users WHERE LastName = 'Smith' AND (City = 'New York' OR C...

Microsoft SQL Server • Getting started with Microsoft SQL Server

Uppercase and Lowercase Strings

To make all the characters in a String uppercase or lowercase: 2.2 let text = "AaBbCc" let uppercase = text.uppercaseString // "AABBCC" let lowercase = text.lowercaseString // "aabbcc" 3.0 let text = "AaBbCc" let uppercase = text.uppercased() // &qu...

Swift Language • Strings and Characters

Installation or Setup

Basic installation: You can download redux javascript file, using this link. Also you can install redux, using bower : bower install https://npmcdn.com/redux@latest/dist/redux.min.js Next, you need to include redux to your page: <html> <head> <script type="text/jav...

redux • Getting started with redux

Grouping in ListView

asp:ListView introduced in ASP.NET WebForms framework 3.5 is the most flexible of all DataPresentation Controls in the framework. An example of Grouping using ListView (which will come handy as an image gallery) Objective: To display three images in a row using asp:ListView Markup <asp:ListVie...

ASP.NET • WebForms

Convenience functions to manipulate data.frames

Some convenience functions to manipulate data.frames are subset(), transform(), with() and within(). subset The subset() function allows you to subset a data.frame in a more convenient way (subset also works with other classes): subset(mtcars, subset = cyl == 6, select = c("mpg", "...

R Language • Data frames

Installation or Setup

Detailed instructions on getting ibm-bluemix set up or installed.

ibm-bluemix • Getting started with ibm-bluemix

If statement

if condition: body The if statements checks the condition. If it evaluates to True, it executes the body of the if statement. If it evaluates to False, it skips the body. if True: print "It is true!" >> It is true! if False: print "This won't get printed.....

Python Language • Conditionals

Else statement

if condition: body else: body The else statement will execute it's body only if preceding conditional statements all evaluate to False. if True: print "It is true!" else: print "This won't get printed.." # Output: It is true! if False: print &...

Python Language • Conditionals

Listening to the long click events

To catch a long click and use it you need to provide appropriate listener to button: View.OnLongClickListener listener = new View.OnLongClickListener() { public boolean onLongClick(View v) { Button clickedButton = (Button) v; String buttonText = clickedButton.getText().toStri...

Android • Button

Using Environment variables to manage Settings across servers

Using environment variables is a widely used way to setting an app's config depending on it environment, as stated in The Twelve-Factor App. As configurations are likely to change between deployment environments, this is a very interesting way to modify the configuration without having to dig in th...

Django • Settings

Enum to string and back

public enum DayOfWeek { Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday } // Enum to string string thursday = DayOfWeek.Thursday.ToString(); // "Thursday" string seventhDay = Enum.GetName(typeof(DayOfWeek), 6); // "Satur...

C# Language • Enum

Installation or Setup

python-requests is available on PyPI, the Python Package Index, which means it can be installed through pip: pip install requests Up-to-date source code can be found on the requests GitHub repository If you wish to install it from source, you can do this by either cloning the GitHub repository:...

python-requests • Getting started with python-requests

Simple data structures

Structure data types are useful way to package related data and have them behave like a single variable. Declaring a simple struct that holds two int members: struct point { int x; int y; }; x and y are called the members (or fields) of point struct. Defining and using structs: ...

C Language • Structs

Substring

Syntax is: SUBSTRING ( string_expression, start, length ). Note that SQL strings are 1-indexed. SELECT SUBSTRING('Hello', 1, 2) --returns 'He' SELECT SUBSTRING('Hello', 3, 3) --returns 'llo' This is often used in conjunction with the LEN() function to get the last n characters of a string of un...

SQL • String Functions