Tutorial by Examples: er

Private inheritance is useful when it is required to restrict the public interface of the class: class A { public: int move(); int turn(); }; class B : private A { public: using A::turn; }; B b; b.move(); // compile error b.turn(); // OK This approach efficiently pr...

# app/channels/appearance_channel.rb class NotificationsChannel < ApplicationCable::Channel def subscribed stream_from "notifications" end def unsubscribed end def notify(data) ActionCable.server.broadcast "notifications", { title: 'New things!', ...

Java-like enumerations can be created by extending Enumeration. object WeekDays extends Enumeration { val Mon, Tue, Wed, Thu, Fri, Sat, Sun = Value } def isWeekend(day: WeekDays.Value): Boolean = day match { case WeekDays.Sat | WeekDays.Sun => true case _ => false } isWeekend...

To avoid verbose null checking, the ?. operator has been introduced in the language. The old verbose syntax: If myObject IsNot Nothing AndAlso myObject.Value >= 10 Then Can be now replaced by the concise: If myObject?.Value >= 10 Then The ? operator is particularly powerful when you...

The NameOf operator resolves namespaces, types, variables and member names at compile time and replaces them with the string equivalent. One of the use cases: Sub MySub(variable As String) If variable Is Nothing Then Throw New ArgumentNullException("variable") End Sub The old sy...

This new feature makes the string concatenation more readable. This syntax will be compiled to its equivalent String.Format call. Without string interpolation: String.Format("Hello, {0}", name) With string interpolation: $"Hello, {name}" The two lines are equivalent and ...

Get the description of an specific property in an object. var sampleObject = { hello: 'world' }; Object.getOwnPropertyDescriptor(sampleObject, 'hello'); // Object {value: "world", writable: true, enumerable: true, configurable: true}

Swift let alert = UIAlertController(title: "Hello", message: "Welcome to the world of iOS", preferredStyle: UIAlertControllerStyle.alert) let defaultAction = UIAlertAction(title: "OK", style: UIAlertActionS...

We write custom action filters for various reasons. We may have a custom action filter for logging, or for saving data to database before any action execution. We could also have one for fetching data from the database and setting it as the global values of the application. To create a custom actio...

With UIAlertController, action sheets like the deprecated UIActionSheet are created with the same API as you use for AlertViews. Simple Action Sheet with two buttons Swift let alertController = UIAlertController(title: "Demo", message: "A demo with two buttons", preferredStyle...

getPreferences(int) returns the preferences saved by Activity's class name as described in the docs : Retrieve a SharedPreferences object for accessing preferences that are private to this activity. This simply calls the underlying getSharedPreferences(String, int) method by passing in this acti...

To get your most recent stash after running git stash, use git stash apply To see a list of your stashes, use git stash list You will get a list that looks something like this stash@{0}: WIP on master: 67a4e01 Merge tests into develop stash@{1}: WIP on master: 70f0d95 Add user role to loca...

The following is an excerpt from Gradle - What is a non-zero exit value and how do I fix it?, see it for the full discussion. Let's say you are developing an application and you get some Gradle error that appears that generally will look like so. :module:someTask FAILED FAILURE: Build failed with...

You can compare BigIntegers same as you compare String or other objects in Java. For example: BigInteger one = BigInteger.valueOf(1); BigInteger two = BigInteger.valueOf(2); if(one.equals(two)){ System.out.println("Equal"); } else{ System.out.println("Not Equal"...

OPERATORS $postsGreaterThan = Post::find()->where(['>', 'created_at', '2016-01-25'])->all(); // SELECT * FROM post WHERE created_at > '2016-01-25' $postsLessThan = Post::find()->where(['<', 'created_at', '2016-01-25'])->all(); // SELECT * FROM post WHERE created_at < '2...

<?php namespace models; use yii\db\ActiveRecord; use yii\behaviors\TimestampBehavior; class Post extends ActiveRecord { public static function tableName() { return 'post'; } public function rules() { ...

To get your most recent stash after running git stash, use git stash apply To see a list of your stashes, use git stash list You will get a list that looks something like this stash@{0}: WIP on master: 67a4e01 Merge tests into develop stash@{1}: WIP on master: 70f0d95 Add user role to lo...

You have to keep the operator precedence in mind when using await keyword. Imagine that we have an asynchronous function which calls another asynchronous function, getUnicorn() which returns a Promise that resolves to an instance of class Unicorn. Now we want to get the size of the unicorn using th...

The Oracle SQL and PL/SQL || operator allows you to concatenate 2 or more strings together. Example: Assuming the following customers table: id firstname lastname --- ----------- ---------- 1 Thomas Woody Query: SELECT firstname || ' ' || lastname || ' is in my database.' a...

Interaction with the history # List all previous commands history # Clear the history, useful if you entered a password by accident history -c Event designators # Expands to line n of bash history !n # Expands to last command !! # Expands to last command starting with "text&qu...