Tutorial by Examples: le

Stateless Component

As the name implies, Stateless Components do not have any local state. They are also known as Dumb Components. Without any local state, these components do not need lifecycle methods or much of the boilerplate that comes with a stateful component. Class syntax is not required, you can simply do con...

react-native • Components

Using .PHONY for non-files targets

Use .PHONY to specify the targets that are not files, e.g., clean or mrproper. Good example .PHONY: clean clean: rm *.o temp Bad example clean: rm *.o temp In the good example make knows that clean is not a file, therefore it will not search if it is or not up to date and will ex...

makefile • .PHONY target

Drawing two rectangles on a

<!DOCTYPE html> <html lang="en"> <head> <meta charset="utf-8" /> <title>Draw two rectangles on the canvas</title> <style> canvas{ border:1px solid gray; } </style> <script async...

HTML • Canvas

Adding multiple dependencies

You can add multiple dependencies. task A << { println 'Hello from A' } task B << { println 'Hello from B' } task C << { println 'Hello from C' } task D << { println 'Hello from D' } Now you can define a set of dependencies: B.dependsOn A...

gradle • Task dependencies

Multiple dependencies with the dependsOn method

You can add multiple dependencies. task A << { println 'Hello from A' } task B(dependsOn: A) << { println 'Hello from B' } task C << { println 'Hello from C' } task D(dependsOn: ['B', 'C'] << { println 'Hello from D' } The output is: >...

gradle • Task dependencies

Remote module RMI

The remote module allows simple RMI (remote method invocation) of main process objects from renderer process. First create the main process in index.js const {app, BrowserWindow} = require('electron') let win = null app.on('ready', () => { win = new BrowserWindow() win.loadURL(`file://...

electron • Main and renderer process.

Exporting .csv files

Exporting using base R Data can be written to a CSV file using write.csv(): write.csv(mtcars, "mtcars.csv") Commonly-specified parameters include row.names = FALSE and na = "". Exporting using packages readr::write_csv is significantly faster than write.csv and does not ...

R Language • Reading and writing tabular data in plain-text files (CSV, TSV, etc.)

Create a Bluetooth LE Advertisement

This example shows how to advertise a custom payload from a Windows 10 device in the foreground. The payload uses a made up company (identified as 0xFFFE) and advertises the string Hello World in the advertisement. BluetoothLEAdvertisementPublisher publisher = new BluetoothLEAdvertisementPublisher(...

bluetooth • Get Started With Bluetooth LE on Windows

Listen for a Bluetooth LE Advertisement

General Listening This example shows how to listen for a specific advertisement. BluetoothLEAdvertisementWatcher watcher = new BluetoothLEAdvertisementWatcher(); // Use active listening if you want to receive Scan Response packets as well // this will have a greater power cost. watcher.Scanni...

bluetooth • Get Started With Bluetooth LE on Windows

implement View.OnLayoutChangeListener in Nativescript

let playerLayoutChangeListener = new android.view.View.OnLayoutChangeListener( { onLayoutChange : function ( v:View, left:number, top:number, right:number, bottom:number, oldLeft:number, oldTop:number, oldRight:number, oldBottom:number):any { if (left != oldLeft || top != oldTop ...

nativescript • implement Interface

Examining Zipfile Contents

There are a few ways to inspect the contents of a zipfile. You can use the printdir to just get a variety of information sent to stdout with zipfile.ZipFile(filename) as zip: zip.printdir() # Out: # File Name Modified Size ...

Python Language • Working with ZIP archives

Error cleanup

In languages such as C, the @goto statement is often used to ensure a function cleans up necessary resources, even in the event of an error. This is less important in Julia, because exceptions and try-finally blocks are often used instead. However, it is possible for Julia code to interface with C ...

Julia Language • @goto and @label

Avoid leaking Activities with Listeners

If you implement or create a listener in an Activity, always pay attention to the lifecycle of the object that has the listener registered. Consider an application where we have several different activities/fragments interested in when a user is logged in or out. One way of doing this would be to h...

Android • Memory Leaks

Working with pathnames and filenames

% set mypath /home/tcluser/sources/tcl/myproject/test.tcl /home/tcluser/sources/tcl/myproject/test.tcl % set dir [file dirname $mypath] /home/tcluser/sources/tcl/myproject % set filename [file tail $mypath] test.tcl % set basefilename [file rootname $filename] test % set extension [file exte...

tcl • Pathnames and filenames

Change selected tab programatically from child Page

You can take a look at the full code in this working Plunker. In this example I use a shared service to handle the communication between the pages inside the tab (child pages) and the tab container (the component that holds the tabs). Even though you probably could do it with Events I like the shar...

ionic2 • Using Tabs

Filter Logoutput by level (log4j 1.x)

You can use a filter to log only messages "lower" than e.g. ERROR level. But the filter is not supported by PropertyConfigurator. So you must change to XML config to use it. See log4j-Wiki about filters. Example "specific level" <appender name="info-out" class=&quo...

Java Language • log4j / log4j2

Custom Click Listener to prevent multiple fast clicks

In order to prevent a button from firing multiple times within a short period of time (let's say 2 clicks within 1 second, which may cause serious problems if the flow is not controlled), one can implement a custom SingleClickListener. This ClickListener sets a specific time interval as threshold (...

Android • Button

Grant/revoke privileges

GRANT SELECT, UPDATE ON Employees TO User1, User2; Grant User1 and User2 permission to perform SELECT and UPDATE operations on table Employees. REVOKE SELECT, UPDATE ON Employees FROM User1, User2; Revoke from User1 and User2 the permission to perform SELECT and UPDATE operations on tab...

SQL • GRANT and REVOKE

Preparing your view controller before a triggering a Segue

PrepareForSegue: func prepareForSegue(_ segue:UIStoryboardSegue, sender sender:AnyObject?) Notifies the view controller that a segue is about to be performed Parameters segue: The segue object. sender: The object that initialized the segue. Example in Swift Perform a task if the ident...

iOS • Segues

Simple Post (Post Fields)

Every instance of WWW with a second parameter is a post. Here is an example to post user id and password to server. void Login(string id, string pwd) { WWWForm dataParameters = new WWWForm(); // Create a new form. dataParameters.AddField("username", id); dataParameter...

unity3d • Communication with server