Tutorial by Examples: di

One use case for assertion is precondition and postcondition. This can be very useful to maintain invariant and design by contract. For a example a length is always zero or positive so this function must return a zero or positive value. #include <stdio.h> /* Uncomment to disable `assert()`...

In this example, we'll be looking at how to store a credit card using the PayPal vault, then reference that stored credit card to process a credit card transaction for a user. The reason why we would want to use the vault is so that we don't have to store sensitive credit card information on our ow...

When an exception object is created (i.e. when you new it), the Throwable constructor captures information about the context in which the exception was created. Later on, this information can be output in the form of a stacktrace, which can be used to help diagnose the problem that caused the excep...

To find files, use the -type f flag $ find . -type f To find directories, use the -type d flag $ find . -type d To find block devices, use the -type b flag $ find /dev -type b To find symlinks, use the -type l flag $ find . -type l

On an ext filesystem, each file has a stored Access, Modification, and (Status) Change time associated with it - to view this information you can use stat myFile.txt; using flags within find, we can search for files that were modified within a certain time range. To find files that have been modifi...

Tuples can be decomposed into individual variables with the following syntax: let myTuple = (name: "Some Name", age: 26) let (first, second) = myTuple print(first) // "Some Name" print(second) // 26 This syntax can be used regardless of if the tuple has unnamed properti...

Occasionally you will find the need to encode binary data as a base64-encoded string. For this we can use the DatatypeConverter class from the javax.xml.bind package: import javax.xml.bind.DatatypeConverter; import java.util.Arrays; // arbitrary binary data specified as a byte array byte[] bi...

To load a properties file bundled with your application: public class Defaults { public static Properties loadDefaults() { try (InputStream bundledResource = Defaults.class.getResourceAsStream("defaults.properties")) { Properties defaults = new ...

You can add an image to your message using the parameter media_url. # Download the twilio-python library from http://twilio.com/docs/libraries from twilio.rest import TwilioRestClient # Find these values at https://twilio.com/user/account account_sid = "ACXXXXXXXXXXXXXXXXX" auth_to...

To send your first SMS with Twilio and Python you'll just need the Twilio-Python helper library to get started. # Download the twilio-python library from http://twilio.com/docs/libraries from twilio.rest import TwilioRestClient # Find these values at https://twilio.com/user/account account_si...

Browse to File > New > Solution to bring you up the new project dialog. Select Android App and press Next. Configure your app by setting your app name and organization ID. Select the Target Platform most suited for your needs, or leave it as the default. Press Next: Set your Project name ...

Browse to File > New > Project to bring you up the New Project dialog. Navigate to Visual C# > Android and select Blank App: Give your app a Name and press OK to create your project. Set up your device for deployment, or configure an emulator To run your application, select the Debug...

There are two types of events emitted by a Preferences object: PreferenceChangeEvent and NodeChangeEvent. PreferenceChangeEvent A PreferenceChangeEvent gets emitted by a Properties object every time one of the node's key-value-pairs changes. PreferenceChangeEvents can be listened for with a Prefer...

All instances of Preferences are always thread-safe across the threads of a single Java Virtual Machine (JVM). Because Preferences can be shared across multiple JVMs, there are special methods that deal with synchronizing changes across virtual machines. If you have an application which is supposed...

A very common guideline in object oriented design is "as little as possible but as much as necessary". This also applies to the strategy pattern: It is usually advisable to hide implementation details, for example which classes actually implement strategies. For simple strategies which do...

This uses the Dropbox Python SDK to upload a file to the Dropbox API from the local file as specified by file_path to the remote path as specified by dest_path. It also chooses whether or not to use an upload session based on the size of the file: f = open(file_path) file_size = os.path.getsize(fi...

Method injection is a fine grained way of injecting dependencies into processing. Consider a method that does some processing based on the current date. The current date is hard to change from a test, so it is much easier to pass a date into the method that you want to test. public void ProcessRe...

Whilst extracting dependencies out of your code so that they can be injected makes your code easier to test, it pushes the problem further up the hierarchy and can also result in objects that are difficult to construct. Various dependency injection frameworks / Inversion of Control Containers have ...

Libraries other than jQuery may also use $ as an alias. This can cause interference between those libraries and jQuery. To release $ for use with other libraries: jQuery.noConflict(); After calling this function, $ is no longer an alias for jQuery. However, you can still use the variable jQuery...

For any file operations, you will need the filesystem module: const fs = require('fs'); Reading a String fs.readFileSync behaves similarly to fs.readFile, but does not take a callback as it completes synchronously and therefore blocks the main thread. Most node.js developers prefer the asynch...