Tutorial by Examples: ch

This example demonstrate how to add caching capabilities to DbProductRepository using Decorator pattern. This approach adheres to SOLID principles because it allows you to add caching without violating Single responsibility principle or Open/closed principle. public interface IProductRepository { ...

Converting between encodings is easy with C++11 and most compilers are able to deal with it in a cross-platform manner through <codecvt> and <locale> headers. #include <iostream> #include <codecvt> #include <locale> #include <string> using namespace std; i...

C++14 In C++14, this is easily done by std::mismatch which returns the first mismatching pair from two ranges: std::string prefix = "foo"; std::string string = "foobar"; bool isPrefix = std::mismatch(prefix.begin(), prefix.end(), string.begin(), string.end()).first == ...

If you have a Form with MinimizeBox and MaximizeBox set to true, then you can not show Help button on title-bar of Form and will lose the feature of click on help button to convert it to help cursor to be able to click on controls to show help. You can make a menu item on MenuStrip act like standar...

Exceptions represent programmer-level bugs like trying to access an array element that doesn’t exist. Errors are user-level issues like trying load a file that doesn’t exist. Because errors are expected during the normal execution of a program. Example: NSArray *inventory = @[@"Sam"...

The following examples will use this class hierarchy: struct A { int m; }; struct B : A {}; struct C : B {}; The conversion from derived class type to base class type is preferred to user-defined conversions. This applies when passing by value or by reference, as well as when converting pointe...

The contents of files and network messages may represent encoded characters. They often need to be converted to unicode for proper display. In Python 2, you may need to convert str data to Unicode characters. The default ('', "", etc.) is an ASCII string, with any values outside of ASCII ...

In this example we create a goroutine (a function running in a separate thread) that accepts a chan parameter, and simply loops, sending information into the channel each time. In the main we have a for loop and a select. The select will block processing until one of the case statements becomes tru...

Pattern matching can also be used to check the type of an instance, rather than using isInstanceOf[B]: val anyRef: AnyRef = "" anyRef match { case _: Number => "It is a number" case _: String => "I...

Create a group of checkboxes that can be used to toggle multiple choices independently. The server will receive the input as a character vector of the selected values. library(shiny) ui <- fluidPage( checkboxGroupInput("checkGroup1", label = h3("This is a Checkbox group&...

Derives from Object Key members public Dispatcher Dispatcher { get; } Summary Most objects in WPF derive from DispatcherObject, which provides the basic constructs for dealing with concurrency and threading. Such objects are associated with a Dispatcher. Only the thread that the Dispatcher w...

Const baseString As String = "Hello World" Dim charLength As Long charLength = Len(baseString) 'charlength = 11

Dim lineOfHyphens As String 'Assign a string with 80 repeated hyphens lineOfHyphens = String$(80, "-")

Dim stringOfSpaces As String 'Assign a string with 255 repeated spaces using Space$ stringOfSpaces = Space$(255) 'Assign a string with 255 repeated spaces using String$ stringOfSpaces = String$(255, " ")

The System.String class supports a number of methods to convert between uppercase and lowercase characters in a string. System.String.ToLowerInvariant is used to return a String object converted to lowercase. System.String.ToUpperInvariant is used to return a String object converted to upper...

To ensure that our collection can be iterated using iterator or for-each loop, we have to take care of following steps: The stuff we want to iterate upon has to be Iterable and expose iterator(). Design a java.util.Iterator by overriding hasNext(), next() and remove(). I have added a simple ...

You should remember that regex was designed for matching a date (or not). Saying that a date is valid is a much more complicated struggle, since it will require a lot of exception handling (see leap year conditions). Let's start by matching the month (1 - 12) with an optional leading 0: 0?[1-9]|1[...

Matching an email address within a string is a hard task, because the specification defining it, the RFC2822, is complex making it hard to implement as a regex. For more details why it is not a good idea to match an email with a regex, please refer to the antipattern example when not to use a ...

Here's how to match a prefix code (a + or (00), then a number from 1 to 1939, with an optional space): This doesn't look for a valid prefix but something that might be a prefix. See the full list of prefixes (?:00|\+)?[0-9]{4} Then, as the entire phone number length is, at most, 15, we can look...

Sometimes it makes sense to nest view's or routes within one another. For example on the dashboard you want several sub views, similar to tabs but implemented via the routing system, to show the users' projects, contacts, messages ets. In order to support such scenarios the router allows us to defin...