Tutorial by Examples: g

First, ensure you have installed mongodb and express via npm. Then, in a file conventionally titled db.js, use the following code: var MongoClient = require('mongodb').MongoClient var state = { db: null, } exports.connect = function(url, done) { if (state.db) return done() M...

The following example is high level coverage of the key concepts and basic skeletal setup:- Collects credentials from the user (Usually from a login screen you've created) Authenticates the credentials with the server (stores custom authentication) Stores the credentials on the device Exte...

A frequent reason why your read operation may not work 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 JavaScript console of you...

Add a -behaviour directive to your module to indicate that it follows a behaviour: -behaviour(gen_server). The American spelling is also accepted: -behavior(gen_server). Now the compiler will give a warning if you've forgotten to implement and export any of the functions required by the beha...

You can define your own behaviour by adding -callback directives in your module. For example, if modules implementing your behaviour need to have a foo function that takes an integer and returns an atom: -module(my_behaviour). -callback foo(integer()) -> atom(). If you use this behaviour in...

In this iText 5 example, we'll change the properties and the value of a text field: public void manipulatePdf(String src, String dest) throws DocumentException, IOException { PdfReader reader = new PdfReader(src); PdfStamper stamper = new PdfStamper(reader, new FileOutputStream(dest)); ...

In this iText 7 example, we'll change the properties and the value of a text field: public void manipulatePdf(String src, String dest) throws IOException { PdfReader reader = new PdfReader(src); PdfDocument pdf = new PdfDocument(reader, new PdfWriter(dest)); PdfAcroForm form = PdfA...

Integer Basics Standard ML of New Jersey v110.78 [built: Thu Jul 23 11:21:58 2015] - 6; val it = 6 : int - ~6; val it = ~6 : int - 6 + ~6; val it = 0 : int Integer Division - 6 div 3; val it = 2 : int - 6 div 4; val it = 0 : int - 3 div 6; val it = 0 : int Integer Value Bounds Us...

Rounding Values midway between two integers go toward the nearest even value. - round(4.5); val it = 4 : int - round(3.5); val it = 4 : int Truncation val it = 4 : int - trunc(4.5); val it = 4 : int - trunc(3.5); val it = 3 : int Floor and Ceiling - ceil(4.5); val it = 5 : int - f...

- real(6); val it = 6.0 : real

JavaFX has a binding API, which provides ways of binding one property to the other. This means that whenever one property's value is changed, the value of the bound property is updated automatically. An example of simple binding: SimpleIntegerProperty first =new SimpleIntegerProperty(5); //create a...

Case 1: While using in the place of method arguments. If a method requires an object of wrapper class as argument.Then interchangeably the argument can be passed a variable of the respective primitive type and vice versa. Example: int i; Integer j; void ex_method(Integer i)//Is a valid statem...

You can access the command line arguments passed to your program using the std::env::args() function. This returns an Args iterator which you can loop over or collect into a Vec. Iterating Through Arguments use std::env; fn main() { for argument in env::args() { if argument == &qu...

For larger command line programs, using std::env::args() is quite tedious and difficult to manage. You can use clap to handle your command line interface, which will parse arguments, generate help displays and avoid bugs. There are several patterns that you can use with clap, and each one provides ...

Jersey (2) uses HK2 as its dependency injection (DI) system. We can use other injection systems, but its infrastructure is built with HK2, and allows us to also use it within our applications. Setting up simple dependency injection with Jersey takes just a few lines of code. Let say for example we ...

Simple way to share a message or link, copy text to clipboard, or open a browser in any Xamarin or Windows app. Available on NuGet : https://www.nuget.org/packages/Plugin.Share/ XAML <StackLayout Padding="20" Spacing="20"> <Button StyleId="Text" Text...

A TabbedPage is similar to a NavigationPage in that it allows for and manages simple navigation between several child Page objects. The difference is that generally speaking, each platform displays some sort of bar at the top or bottom of the screen that displays most, if not all, of the availabl...

Spring Boot is a bootstrapping framework for Spring applications. It has seamless support for integrating with Jersey also. One of the advantages of this (from the perspective of a Jersey user), is that you have access to Spring's vast ecosystem. To get started, create a new standalone (non-wepapp)...

Create managed bean To create a manage bean you need the annotation @ManagedBean for example: @ManagedBean public class Example {} You need the package: import javax.faces.bean.ManagedBean; Managed bean Scope We use annotations to define the scope in which the bean will be stored. There...

GNU make This pairmap function takes three arguments: A function name First space-separated list Second space-separated list For each zipped tuple in the lists it will call the function with the following arguments: Tuple element from the first list Tuple element from the second list ...