Tutorial by Examples: a

If we have a Model as following, from django.db import models from django.contrib.auth.models import User class UserModuleProfile(models.Model): user = models.OneToOneField(User) expired = models.DateTimeField() admin = models.BooleanField(default=False) employee_id = models...

To view an browse Vaadin add-ons in the Directory, you must be registered to vaadin.com. After the initial discovery of artifact details, e.g. for download and usage, registration is not required. Also, the usage of add-ons in a Maven project is not IDE-specific and the same instructions apply. Fro...

Partial classes provide a clean way to separate core logic of your scripts from platform specific methods. Partial classes and methods are marked with the keyword partial. This signals the compiler to leave the class "open" and look in other files for the rest of the implementation. // E...

CoffeeScript provides a basic class structure that allows you to name your class, set the superclass, assign prototypal properties, and define the constructor, in a single assignable expression. Small example below: class Animal constructor: (@name) -> move: (meters) -> alert @n...

flatMap is similar to map. The difference is described by the javadoc as follows: This method is similar to map(Function), but the provided mapper is one whose result is already an Optional, and if invoked, flatMap does not wrap it with an additional Optional. In other words, when you chain a...

The & operator is the parent selector. When used in or as a selector, it is replaced with the full parent selectors (entire sequence of selectors right upto to the topmost level of a nested block) in the final CSS output. It is useful when creating nested rules that require using the parent sel...

Less allows the usage of the parent selector (&) anywhere in a complex selector and thus allows changing styles when the current element is within another element which gives it a different context: For example, in the below code the parent selector is placed at the end and thus it actually be...

Import the class, which contains the method to be tested. Perform the operation with dummy data. Now compare the result of operation with expected result. - (void)testReverseString{ NSString *originalString = @"hi_my_name_is_siddharth"; NSString *reversedString = [self.someObject ...

- (void)testDoSomethingThatTakesSomeTime{ XCTestExpectation *completionExpectation = [self expectationWithDescription:@"Long method"]; [self.someObject doSomethingThatTakesSomeTimesWithCompletionBlock:^(NSString *result) { XCTAssertEqualObjects(@"result", result, @"Re...

1. For Synchronous methods : - (void)testPerformanceReverseString { NSString *originalString = @"hi_my_name_is_siddharth"; [self measureBlock:^{ [self.someObject reverseString:originalString]; }]; } 2. For Asynchronous methods : - (void)testPerformanceOfAsynch...

You want to add a signature to a PDF in a way that a standard conform PDF viewer (e.g. Adobe Reader) will recognize, display, and validate as an integrated PDF signature. In that case you cannot simply externally create a signature covering the original PDF as is and expect to now have to merely so...

If multiple signatures are to be integrated into a PDF, this is done by means of incremental PDF updates (explicitly not by adding multiple SignerInfo structures to a single integrated CMS signature container!): The cryptographic verification of these signatures merely guarantees that the byte ra...

Install PDFTK Server from https://www.pdflabs.com/tools/pdftk-server/ PDFtk Server is a command line tool which can: • Merge PDF Documents or Collate PDF Page Scans • Split PDF Pages into a New Document • Rotate PDF Documents or Pages • Decrypt Input as Necessary (Password Required...

The way Moment uses dates and times is by wrapping the existing Date() object in a moment() object and specifying useful and intuitive methods on this object. Format Dates moment().format('MMMM Do YYYY, h:mm:ss a'); // August 4th 2016, 10:41:45 am moment().format('dddd'); // Th...

Functions are found by first collecting a set of "associated classes" and "associated namespaces" that include one ore more of the following, depending on the argument type T. First, let us show the rules for classes, enumeration and class template specialization names. If T i...

This example demonstrates how you can respond to a button click by performing some work on a worker thread and then update the user interface to indicate completion void MyButton_OnClick(object sender, EventArgs args) { Task.Run(() => // Schedule work using the thread pool { ...

C++11 Motivational example When you have a variadic template pack in the template parameters list, like in the following code snippet: template<typename ...Args> void func(Args &&...args) { //... }; The standard library (prior to C++17) offers no direct way to write enable_if...

psycopg2 is the most popular PostgreSQL database adapter that is both lightweight and efficient. It is the current implementation of the PostgreSQL adapter. Its main features are the complete implementation of the Python DB API 2.0 specification and the thread safety (several threads can share t...

<Image x:Name="MyImage" /> // Show image from web MyImage.Source = new BitmapImage(new Uri("http://your-image-url.com")) // Show image from solution MyImage.Source = new Uri("ms-appx:///your-image-in-solution", UriKind.Absolute) // Show image from file ...

<TextBlock x:Name="MyControl" Text="Hello, world!" /> var rtb = new RenderTargetBitmap(); await rtb.RenderAsync(MyControl); // Render control to RenderTargetBitmap // Get pixels from RTB IBuffer pixelBuffer = await rtb.GetPixelsAsync(); byte[] pixels = ...