Tutorial by Examples: er

The following configuration options should be called on a Rails::Railtie object config.after_initialize: Takes a block which will be run after rails has initialized the application. config.asset_host: This sets the host for the assets. This is useful when using a Content Delivery Network. This i...

Rails allows you to configure what generators are used when running rails generate commands. This method, config.generators takes a block config.generators do |g| g.orm :active_record g.test_framework :test_unit end Here are some of the options OptionDescriptionDefaultassetsCreates asset...

Merge Sort is a divide-and-conquer algorithm. It divides the input list of length n in half successively until there are n lists of size 1. Then, pairs of lists are merged together with the smaller first element among the pair of lists being added in each step. Through successive merging and through...

After installing Julia, to launch the read-eval-print-loop (REPL): On Unix Systems Open a terminal window, then type julia at the prompt, then hit Return. You should see something like this come up: On Windows Find the Julia program in your start menu, and click it. The REPL should be launched...

The Julia REPL is an excellent calculator. We can start with some simple operations: julia> 1 + 1 2 julia> 8 * 8 64 julia> 9 ^ 2 81 The ans variable contains the result of the last calculation: julia> 4 + 9 13 julia> ans + 9 22 We can define our own variables usi...

We have a tree data type like this: data Tree a = Tree a [Tree a] deriving Show And we wish to write a function that assigns a number to each node of the tree, from an incrementing counter: tag :: Tree a -> Tree (a, Int) The long way First we'll do it the long way around, since it illust...

To easily convert all tables in one database, use the following: SET @DB_NAME = DATABASE(); SELECT CONCAT('ALTER TABLE `', table_name, '` ENGINE=InnoDB;') AS sql_statements FROM information_schema.tables WHERE table_schema = @DB_NAME AND `ENGINE` = 'MyISAM' AND `TABLE_TYPE` = '...

@Entity @Table(name="FOO") public class Foo { private UUID fooId; @OneToMany(mappedBy = "bar") private List<FooBar> bars; } @Entity @Table(name="BAR") public class Bar { private UUID barId; @OneToMany(mappedBy = "f...

@Entity @Table(name="FOO") public class Foo { private UUID fooId; @OneToMany @JoinTable(name="FOO_BAR", joinColumns = @JoinColumn(name="fooId"), inverseJoinColumns = @JoinColumn(name="barId")) private List<Bar&g...

@Entity @Table(name="FOO") public class Foo { private UUID fooId; @OneToOne(cascade = CascadeType.ALL) @JoinColumn(name = "barId") private Bar bar; } @Entity @Table(name="BAR") public class Bar { private UUID barId; ...

@Entity @Table(name="FOO") public class Foo { private UUID fooId; @OneToMany @JoinTable(name="FOO_BAR", joinColumns = @JoinColumn(name="fooId"), inverseJoinColumns = @JoinColumn(name="barId", unique=true)) private ...

@Entity @Table(name="FOO") public class Foo { private UUID fooId; @OneToOne private Bar bar; } @Entity @Table(name="BAR") public class Bar { private UUID barId; //No corresponding mapping to Foo.class } Specifies a one-way relationship b...

TestSchedulers allows you to control time and execution of Observables instead of having to do busy waits, joining threads or anything to manipulate system time. This is VERY important if you want to write unit tests that are predictable, consistent and fast. Because you are manipulating time, the...

import org.bukkit.event.Listener; import org.bukkit.event.EventHandler; import org.bukkit.event.EventPriority; import org.bukkit.event.player.PlayerLoginEvent; import org.bukkit.event.player.PlayerQuitEvent; public class MyEventListener implements Listener { /** * Constructor ...

An Observable can be thought of as just a stream of events. When you define an Observable, you have three listeners: onNext, onComplete and onError. onNext will be called every time the observable acquires a new value. onComplete will be called if the parent Observable notifies that it finished prod...

import serial #Serial takes these two parameters: serial device and baudrate ser = serial.Serial('/dev/ttyUSB0', 9600)

Initialize serial device import serial #Serial takes two parameters: serial device and baudrate ser = serial.Serial('/dev/ttyUSB0', 9600) to read single byte from serial device data = ser.read() to read given number of bytes from the serial device data = ser.read(size=5) to read one li...

Custom Renderer help to allows to add new properties and render them differently in native platform that can not be otherwise does through shared code. In this example we will add radius and shadow to a boxview. Firstly, we should create custom control in PCL project, which will declare some requir...

Instead of using regex, the Lua string library has a special set of characters used in syntax matches. Both can be very similar, but Lua pattern matching is more limited and has a different syntax. For instance, the character sequence %a matches any letter, while its upper-case version represents al...

Creating a chart that displays a static dataset is relatively simple. For example, if we have this array of objects as the data: var data = [ {title: "A", value: 53}, {title: "B", value: 12}, {title: "C", value: 91}, {title: "D", value: 24...