Tutorial by Examples: w

Type erasing type erasure with std::any

This example uses C++14 and boost::any. In C++17 you can swap in std::any instead. The syntax we end up with is: const auto print = make_any_method<void(std::ostream&)>([](auto&& p, std::ostream& t){ t << p << "\n"; }); super_any<decltype(print...

C++ • Type Erasure

Hello World!

"Hello World!" Also, check out the detailed discussion of how, when, whether and why to print a string.

R Language • Getting started with R Language

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

Hello world!

import React, { Component } from 'react'; import { AppRegistry, Text } from 'react-native'; class HelloWorldApp extends Component { render() { return ( <Text>Hello world!</Text> ); } } AppRegistry.registerComponent('HelloWorldApp', () => HelloWorldApp); ...

react-native • Hello World

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

Draw behind existing shapes with "destination-over"

context.globalCompositeOperation = "destination-over" "destination-over" compositing places new drawing under existing drawings. context.drawImage(rainy,0,0); context.globalCompositeOperation='destination-over'; // sunny UNDER rainy context.drawImage(sunny,0,0);

html5-canvas • Compositing

Erase existing shapes with "destination-out"

context.globalCompositeOperation = "destination-out" "destination-out" compositing uses new shapes to erase existing drawings. The new shape is not actually drawn -- it is just used as a "cookie-cutter" to erase existing pixels. context.drawImage(apple,0,0); conte...

html5-canvas • Compositing

Default compositing: New shapes are drawn over Existing shapes

context.globalCompositeOperation = "source-over" "source-over" compositing [default], places all new drawings over any existing drawings. context.globalCompositeOperation='source-over'; // the default context.drawImage(background,0,0); context.drawImage(parachuter,0,0); ...

html5-canvas • Compositing

Clip images inside shapes with "destination-in"

context.globalCompositeOperation = "destination-in" "destination-in" compositing clips existing drawings inside a new shape. Note: Any part of the existing drawing that falls outside the new drawing is erased. context.drawImage(picture,0,0); context.globalCompositeOperation...

html5-canvas • Compositing

Clip images inside shapes with "source-in"

context.globalCompositeOperation = "source-in"; source-in compositing clips new drawings inside an existing shape. Note: Any part of the new drawing that falls outside the existing drawing is erased. context.drawImage(oval,0,0); context.globalCompositeOperation='source-in'; // pictu...

html5-canvas • Compositing

Detect errors when writing a value on Android

There are many reasons a write operation may fail. A frequent one is because your security rules reject the operation, for example because you're not authenticated (by default a database can only be accessed by an authenticated user). You can see these security rule violations in the logcat output....

firebase • How do I listen for errors when accessing the database?

Ordering with the mustRunAfter method

task A << { println 'Hello from A' } task B << { println 'Hello from B' } B.mustRunAfter A The B.mustRunAfter A line tells Gradle to run task after task specified as an argument. And the output is: > gradle -q B A Hello from A Hello from B The ordering rule d...

gradle • Ordering tasks

Adding a ViewPager

Make sure the following dependency is added to your app's build.gradle file under dependencies: compile 'com.android.support:support-core-ui:25.3.0' Then add the ViewPager to your activity layout: <android.support.v4.view.ViewPager android:id="@+id/viewpager" android:layo...

Android • ViewPager

Customizing the CardView

CardView provides a default elevation and corner radius so that cards have a consistent appearance across the platforms. You can customize these default values using these attributes in the xml file: card_view:cardElevation attribute add elevation in CardView. card_view:cardBackgroundColor attr...

Android • CardView

Finding all branches with no merged changes

Sometimes you might have branches lying around that have already had their changes merged into master. This finds all branches that are not master that have no unique commits as compared to master. This is very useful for finding branches that were not deleted after the PR was merged into master. ...

Git • Merging

Showing additional information when an exception occurs

It's important to handle exceptions in your service. When developing the service, you can set the WCF to provide more detailed information, adding this tag to configuration file, usually Web.config: <serviceDebug includeExceptionDetailInFaults="true"/> This tag must be placed w...

wcf • Handling exceptions

Throwing a user-friendly message with FaultException

You can handle exceptions and throw a most friendly message like 'Unavailable service' throwing a FaultException: try { // your service logic here } catch (Exception ex) { // You can do something here, like log the original exception throw new FaultException("There was a pro...

wcf • Handling exceptions

Throwing a FaultException with a Fault Code

The FaultException can also includes a FaultCode, that is a string data you can use to pass additional information, so the client can be able to distinguish different exceptions: try { // your service logic here } catch (Exception ex) { throw new FaultException("There was a proble...

wcf • Handling exceptions

One way: use a custom listener defined in your C# code

It took me a while to get this right, so I decided to share a solution because it might save someone else several days of trial and error. The problem: I want to be able to enable/disable WCF tracing in my C# .NET application and choose the trace output filename. I don't want users editing the .con...

wcf • How to: Disable/Enable WCF tracing in C# application code

DROPPING A VIEW

-- Create and drop a view in the current database. CREATE VIEW few_rows_from_t1 AS SELECT * FROM t1 LIMIT 10; DROP VIEW few_rows_from_t1; -- Create and drop a view referencing a table in a different database. CREATE VIEW table_from_other_db AS SELECT x FROM db1.foo WHERE x IS NOT NULL; DROP V...

MySQL • VIEW