Tutorial by Examples: en

Declaring non-type template arguments with auto

Prior to C++17, when writing a template non-type parameter, you had to specify its type first. So a common pattern became writing something like: template <class T, T N> struct integral_constant { using type = T; static constexpr T value = N; }; using five = integral_constant&l...

C++ • Templates

Rename a Remote Repository

Rename the remote named <old> to <new>. All remote-tracking branches and configuration settings for the remote are updated. To rename a remote branch name dev to dev1 : git remote rename dev dev1

Git • Git Remote

Implementing Hashable protocol

Types used in Sets and Dictionaries(key) must conform to Hashable protocol which inherits from Equatable protocol. Custom type conforming to Hashable protocol must implement A calculated property hashValue Define one of the equality operators i.e. == or !=. Following example implements Hasha...

Swift Language • Protocols

Creating an array of sequential numbers

LINQ provides a method that makes it easy to create a collection filled with sequential numbers. For example, you can declare an array which contains the integers between 1 and 100. The Enumerable.Range method allows us to create sequence of integer numbers from a specified start position and a num...

C# Language • Arrays

Login example in the Model View Presenter (MVP) pattern

Let's see MVP in action using a simple Login Screen. There are two Buttons—one for login action and another for a registration screen; two EditTexts—one for the email and the other for the password. LoginFragment (The View) public class LoginFragment extends Fragment implements LoginContract.Prese...

Android • MVP Architecture

Implementing map in RPG game

Flyweight is one of structural design patterns. It is used to decrease the amount of used memory by sharing as much data as possible with similiar objects. This document will teach you how to use Flyweight DP properly. Let me explain the idea of it to you on a simple example. Imagine you're working...

C# Language • Implementing Flyweight Design Pattern

Saving and Restoring Fragment State

Fragments also have a onSaveInstanceState() method which is called when their state needs to be saved: public class MySimpleFragment extends Fragment { private int someStateValue; private final String SOME_VALUE_KEY = "someValueToSave"; // Fires when a configuration ch...

Android • Orientation Changes

Retaining Fragments

In many cases, we can avoid problems when an Activity is re-created by simply using fragments. If your views and state are within a fragment, we can easily have the fragment be retained when the activity is re-created: public class RetainedFragment extends Fragment { // data object we want to ...

Android • Orientation Changes

Locking Screen Orientation

If you want to lock the screen orientation change of any screen (activity) of your android application you just need to set the android:screenOrientation property of an <activity> within the AndroidManifest.xml: <activity android:name="com.techblogon.screenorientationexample.Main...

Android • Orientation Changes

Prevent binding on PostModel

Considering a (post)model: public class User { public string FirstName { get; set; } public bool IsAdmin { get; set; } } With a view like so: @using (Html.BeginForm()) { @Html.EditorFor(model => model.FirstName) <input type="submit" value="Save" /...

asp.net-mvc • Model binding

Checking if running inside a virtual environment

Sometimes the shell prompt doesn't display the name of the virtual environment and you want to be sure if you are in a virtual environment or not. Run the python interpreter and try: import sys sys.prefix sys.real_prefix Outside a virtual, environment sys.prefix will point to the system p...

Python Language • Virtual environments

IComparable as an Example of Implementing an Interface

Interfaces can seem abstract until you seem them in practice. The IComparable and IComparable<T> are great examples of why interfaces can be helpful to us. Let's say that in a program for a online store, we have a variety of items you can buy. Each item has a name, an ID number, and a price. ...

C# Language • Interfaces

A simple authentication POST request with Jsoup

A simple POST request with authentication data is demonstrated below, note that the username and password field will vary depending on the website: final String USER_AGENT = "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36"; ...

Jsoup • Logging into websites with Jsoup

A more comprehensive authentication POST request with Jsoup

Most websites require a much more complicated process than the one demonstrated above. Common steps for logging into a website are: Get the unique cookie from the initial login form. Inspect the login form to see what the destination url is for the authentication request Parse the login form t...

Jsoup • Logging into websites with Jsoup

Parsing JavaScript Generated Page with Jsoup and HtmUnit

page.html - source code <html> <head> <script src="loadData.js"></script> </head> <body onLoad="loadData()"> <div class="container"> <table id="data" border="1"> <...

Jsoup • Parsing Javascript Generated Pages

Enable streaming from flask

Flask has that feature which lets you stream data from a view by using generators. Let's change the app.py file add from flask import Response add from datetime import datetime add from time import sleep create a new view: @app.route("/time/") def time(): def streamer(): ...

Flask • Deploying Flask application using uWSGI web server with Nginx

Detecting when UIScrollView finished scrolling with delegate methods

scrollViewDidEndDecelerating: this tells the delegate that the scroll view has ended decelerating the scrolling movement. Objective C: - (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView { [self stoppedScrolling]; } - (void)scrollViewDidEndDragging:(UIScrollView *)scrollView w...

iOS • UIScrollView

Fencepost Sums

Here we consider sums of the form a + b + a + b + ... a vs. a + b + a + b + ... b To visualize these sums, imagine a section of fence alternating between posts and rails. Three scenarios are possible. Imagine a section of fence with posts at each end, connected by rails. n rails require...

math • Common summations in computer science

SQLiteOpenHelper with fully qualified DB path name/databse in public folder

Normally Android-SQLiteOpenHelper does not allow fully qualified path names where the database should be stored. So public database files are not possible. You can use the SQLiteOpenHelper with a custom path if you provide a custom ContextClass and if you have write access in the target directory. ...

android-sqlite • SQLiteOpenHelper

Verifying Arguments with ArgumentMatcher

Mockito provides a Matcher<T> interface along with an abstract ArgumentMatcher<T> class to verify arguments. It uses a different approach to the same use-case than the ArgumentCaptor. Additionally the ArgumentMatcher can be used in mocking too. Both use-cases make use of the Mockito.argT...

mockito • Getting started with mockito