Introducing the Quic Web Development Framework - Part 3

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Introduction

Quic is a web development framework that enables you create rich web applications with less code than is usually needed.
Quic is basically a preprocessor; it goes through your HTML file, looking for custom tags, and producing standard HTML, CSS, JavaScript (and pretty much anything) from such tags.
When a custom tag is encountered Quic loads the appropriate assembly and locates a class with the same name as the tag. The class is then instantiated, and its Render method is called to emit the relevant codes and/or files.
So we can say Quic allows you to delegate the dirty jobs to a class, and include that class in your HTML file as a custom tag.

Background

In the first part of this article ( Introducing the Quic Web Development Framework - Part 1) we were introduced to the Quic framework, its uses, the ideas behind it, and its advantages.
We ended the article with a healthy discussion of the Quic-specific attributes expected in a <html> tag.
In the second part of this article ( Introducing the Quic Web Development Framework - Part 2) we looked at the Quic-compliant <head> tag, resource elements, the Quic-compliant <body> tag, UI elements, and value providers.
We ended the article with a suggestion that every Quic DLL file be accompanied with a manifest file describing the elements (as well as value providers, file initializers) contained within that DLL file.
In this article, we'll look at how to create your own Quic elements, and various miscellaneous topics.
To successfully follow the source codes in this framework, all you need is a healthy knowledge of C#. Two of the core namespaces used are System.Xml.Linq (I previously used System.Xml, but found it difficult retrieving line number and column number information) and System.Reflection to help me load the relevant assemblies and classes.

Output Comments

Normally comments in the source file are ignored, and will not appear in the output file. To make a comment appear in the output file, start it with <!--out:. That is, add the text "out:" (with the colom) after the tokens that normally introduce a comment. Now the comment will be rendered to the output, but without the "out:" characters.
This comment in the source file:

<!--out: render this comment-->

will be rendered as this in the output file:

<!--render this comment-->

Loop and LoopCount

Every Quic element comes with a Loop property which can be set in markup. This property tells the element how many times it should render itself to the output file. The default value for Loop is one, which means the element should render itself only once.

<Button Loop="3">First set of buttons</Button>
<Button Loop="3" Text="Second set of buttons" />

This feature comes in handy when you need to repeat the same tag multiple times. For instance, you could use this to give a table identical rows or to give a list identical list items. To print out the number of times an element has rendered itself, query the LoopCount property. Currently this property does not work well in containers (it always returns 1). Also, you have to use it in a lazy evaluation (or it would return 0). These are limitations that would be addressed in a future release.

<Button Loop="3">{?String {$LoopCount}}</Button>
<Button Loop="3" Text="{?String {$LoopCount}}" />

Model/Data Binding

Model or data binding is not supported natively in Quic yet. Since Quic allows you to work effortlessly with various other frameworks like Angular and React, you can leverage the model/data binding they provide.

Quic is XML-Compliant

Always remember that your Quic file should be an XML-compliant file, and is therefore subject to the same rules that govern XML. For instance, never forget to use & to output &.

<![CDATA[...]]>

You can use <![CDATA[my escaped text]]> to escape text. Quic will print out the escaped text verbatim in the output file. This can be useful when you wish to render scripts that have characters that break the XML validation rules. Just insert the entire script within a <![CDATA[...]]> block.
If CDATA is not sufficient (most probably because you need to include "]]>" in the escaped text), use the special comment .
This comment in the source file:

<!--cdata: <script>if (a > b) alert("greater than");</script>-->

will be rendered as this in the output file:

<script>if (a > b) alert("greater than");</script>

Creating Your Own Quic Elements

Workflow Overview

The workflow of the entire system has been partially explained in the first part of this series.
The first significant thing that needs to be done is to create an instance of Quic.QuicDocument [Quic\Core\QuicDocument.cs]. As the name implies, this object represents the document/file we have to interact with. The class Quic.QuicDocument has no public constructors; you obtain an instance of the class by calling the static method Load, and passing the file path to the XML source file as argument.

QuicDocument doc = QuicDocument.Load(@"c:\path\to\file.xml");

This method parses the source XML file (with the help of an instance of System.Xml.Linq.XDocument), and builds a tree of Quic elements with the help of the QuicDocument.BuildElement method.
The QuicDocument.Load method passes each relevant System.Xml.Linq.XNode object (most of which represent XML tags) to the QuicDocument.BuildElement method.
The QuicDocument.BuildElement method then passes relevant information gotten from the System.Xml.Linq.XNode object (like tag local name, tag namespace prefix) to the QuicDocument.BuildObject method.
The QuicDocument.BuildObject method uses the data it receives to load the appropriate assembly (System.Reflection.Assembly) and create the appropriate object (using System.Activator). The created object is then returned back to the QuicDocument.BuildElement method.
The QuicDocument.BuildElement method converts the returned object (System.Object) into a Quic element (Quic.Element), and returns it to the QuicDocument.Load method, which then stores the object for future processing. Having successfully created the instance of the Quic.QuicDocument, the next significant thing to do is to produce the output file(s). Typically, more than one file is produced as output, so an output directory to contain all output files is specified. The method that produces the output files is the Quic.Render method, and it accepts as argument the path to the output directory.

doc.Render(@"c:\path\to\output\directory");

Essentially, what this method does is to call the Element.BeginRender (not the Element.Render) method of each Quic element in the document. The Element.Render method should not be called directly, instead the Element.BeginRender method should be called as it does some preparatory works before calling the Element.Render method. We will touch on this again shortly. The Quic.QuicDocument class exposes three read-only properties that are important during any render session.

OutputDirectory: Gets the output directory for the current render session.
OutputFile: Gets the main output file for the current render session.
OutputOptions: This is not yet used, but should hold options/settings that affect the current render session.

That's about it about the Quic.QuicDocument class, and the general workflow of the system.

Quic.Element

To create a Quic element, you must inherit (directly or indirectly) from the abstract class Quic.Element [Quic\Core\Elements\Element.cs].
Public properties you define in your element class can be accessed from markup (usually as the attribute of a corresponding tag), and public read-write properties can even be set from markup. To prevent a public property from being visible to markup, apply the [NotQuicProperty] attribute (located at Quic\Attributes\NotQuicPropertyAttribute.cs) to the property.
Quic.Element defines a very important virtual method:

public virtual IValueProvider GetImplicitValueProvider(string propertyName, Type propertyType)

This method supplies value providers that help convert string attribute values gotten from markup to actual objects of appropriate data types, which are then assigned to the appropriate properties of the Quic element. The implicit value providers registered for Quic.Element are not often sufficient. This is why you have the liberty to override the GetImplicitValueProvider method. This is exactly what we do in a number of Quic.Bootstrap.dll elements. For instance, the very core class BootstrapElement [Quic.Bootstrap\Elements\BootstrapElement.cs] provides its own implementation of the GetImplicitValueProvider method:

public override IValueProvider GetImplicitValueProvider(string propertyName, Type propertyType)
{
  if (propertyName == "Align")
  {
    return AlignmentProvider.Singleton();
  }
  else if (propertyName == "State")
  {
    return StateProvider.Singleton();
  }
  else if (propertyName == "Validation")
  {
    return ValidationStateProvider.Singleton();
  }

  return base.GetImplicitValueProvider(propertyName, propertyType);
}

Check out the source codes for the implicit value providers registered in various Quic.Bootstrap.dll elements in Quic.Bootstrap\ValueProviders\.
Value providers were covered in greater detail in the second part of this series. Quic.Element defines an abstract method:

public abstract void Render();

This is probably the most important method you need to implement in your base class, as this is the method called to emit the output texts and/or files. Quic.Element exposes some very important properties:

```
public virtual string Name { get {...} set {...} }
```
This is the name of the element, and should be unique throughout the containing document.
```
[NotQuicProperty]
public QuicDocument Document { get; set; }
```
This exposes the Quic.QuicDocument instance that holds this element. The element can then query for Document.OutputDirectory, Document.OutputFile, and Document.OutputOptions, which were described earlier on.
```
[NotQuicProperty]
public bool IsContainer { get; set; }
```
This determines whether the Quic element can have children or not.
```
[NotQuicProperty]
public ElementCollection Elements { get {...} }
```
Whenever a tag on the markup file is not empty and it's matching Quic element is a container, the content of such tag is parsed into a collection of Quic elements, and those elements are stored in this property.
```
public string Content { get; set; }
```
Whenever a tag on the markup file is not empty but it's matching Quic element is not a container, the content of such tag is stored in this property.

If a Quic element has children, it is the resposibility of the parent element to call the Render methods of its children, usually during its own Render operation. Nevertheless, you should not call the Render method directly; instead, call the BeginRender method. BeginRender does some preparatory tasks (like evaluating lazy properties) and then calls Render the appropriate number of times, as defined by the Loop property.
Although you can inherit from Quic.Element directly, you should inherit from either Quic.UIElement or Quic.ResourceElement.

Extending `Quic.UIElement`

If an element is meant to contribute to the user interface of the document, let the element extend Quic.UIElement [Quic\Core\Elements\UIElement.cs]. This is a very small and simple class that adds a few properties that are expected in a UI element.

Extending `Quic.ResourceElement`

If an element is not meant to contribute to the user interface of the document (perhaps it simply provides a service used by other elements), let the element extend Quic.ResourceElement [Quic\Core\Elements\ResourceElement.cs]. This class provides one very important property:

public virtual string Key { get {...} set {...} }

The use of this property was covered in the second part of this series.

Messaging

You can send messages from your Quic elements to the Quic environment (the CLI or the GUI Quic Bar). Currently there are two ways to send such messages:

As a prompt
As a notification

To send messages, you use the Quic.Messaging.Messenger class [Quic\Messaging\Messenger.cs].

Messenger.Prompt

When a prompt is sent from your Quic element to the environment, the Quic Bar graphical user interface (GUI) handles it by raising a dialog/message box while the command line interface (CLI) writes the message of the prompt to the console window.
To send prompts, you call the Messenger.Prompt method:

public static void Prompt(string message, MessageType messageType)

The first argument you pass is the message itself.
The second argument represents the type of message you are sending. This may affect how the environment treats the message.
Quic.Messaging.MessageType [Quic\Messaging\MessageType.cs] is an enum defined as shown below:

public enum MessageType
{
  Error,
  Info,
  Question,
  Success,
  Warning
}

Messenger.Notify

When a notification is sent from your Quic element to the environment, the command line interface (CLI) writes the message of the notification to the console window while the Quic Bar graphical user interface (GUI) handles it by changing the notification icon to the right of the bar and adding the message to the notification tray.

To send notifications, you call the Messenger.Notify method:

public static void Notify(INotification notification)

The argument you pass should implement the interface Quic.Messaging.INotification [Quic\Messaging\INotification.cs] which is defined as shown below:

public interface INotification
{
  string Message { get; }
  MessageType MessageType { get; }
  string FilePath { get; }
  int Line { get; }
  int Column { get; }
  bool HasLineInfo { get; }
}

You should never throw exceptions from your Quic elements to the environment; they will not be caught. Instead, you should create an instance of Quic.QuicException [Quic\Exceptions\QuicException.cs] and pass it as the argument of a Messenger.Notify call. This is possible because Quic.QuicException implements the Quic.Messaging.INotification interface.

Trying to Keep it Short

There are a few more topics to touch but the article is getting too long. The major remaining topics are:

Creating Your Own Value Providers
Creating Your Own File Initializers
Creating Your Own Output Files

These concepts were touched in the second part of this series, and can be easily understood by looking at the project source code.

That 1990 Hackaholic

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Monday 20 June 2016