Where's the cart? Now you can get everything with O'Reilly Online Learning. It's the most comprehensive book available on HTML and XHTML today. It covers . " lucid, in-depth descriptions of the behavior of every HTML tag on every major browser and platform, plus enough dry humor to make the book a pleasure to. A proper plan can improve your code, including your HTML documents and CSS style sheets. Jens Oliver Meiert explores the theory and practice of coding.
|Language:||English, Spanish, Hindi|
|Genre:||Children & Youth|
|Distribution:||Free* [*Register to download]|
Your complete HTML & CSS video course: Learn the fundamentals of HTML and CSS, and master hands-on, real-world skills DescriptionIn Learning HTML & CSS LiveLessons, Jennifer Kyrnin helps you master the core Books & Videos . Tired of reading HTML books that only make sense after you're an expert? Then it's about time you picked up the newly revised Head First HTML and CSS and. The third edition of HTML: The Definitive Guide brings it all together for you. It is the most comprehensive book available on HTML today. It covers Netscape.
In the GoF book, the applicability of the Singleton pattern is described as follows: There must be exactly one instance of a class, and it must be accessible to clients from a well-known access point. When the sole instance should be extensible by subclassing, and clients should be able to use an extended instance without modifying their code.
The second of these points refers to a case where we might need code such as: mySingleton. FooSingleton above would be a subclass of BasicSingleton and implement the same interface. Why is deferring execution considered important for a Singleton? It is important to note the difference between a static instance of a class object and a Singleton: whilst a Singleton can be implemented as a static instance, it can also be constructed lazily, without the need for resources nor memory until this is actually needed.
If we have a static object that can be initialized directly, we need to ensure the code is always executed in the same order e. Both Singletons and static objects are useful but they shouldn't be overused - the same way in which we shouldn't overuse other patterns.
In practice, the Singleton pattern is useful when exactly one object is needed to coordinate others across a system. They're often an indication that modules in a system are either tightly coupled or that logic is overly spread across multiple parts of a codebase.
Singletons can be more difficult to test due to issues ranging from hidden dependencies, the difficulty in creating multiple instances, difficulty in stubbing dependencies and so on. Miller Medeiros has previously recommended this excellent article on the Singleton and its various issues for further reading as well as the comments to this article, discussing how Singletons can increase tight coupling.
I'm happy to second these recommendations as both pieces raise many important points about this pattern that are also worth noting. The Observer Pattern The Observer is a design pattern where an object known as a subject maintains a list of objects depending on it observers , automatically notifying them of any changes to state.
When a subject needs to notify observers about something interesting happening, it broadcasts a notification to the observers which can include specific data related to the topic of the notification. When we no longer wish for a particular observer to be notified of changes by the subject they are registered with, the subject can remove them from the list of observers.
It's often useful to refer back to published definitions of design patterns that are language agnostic to get a broader sense of their usage and advantages over time. The definition of the Observer pattern provided in the GoF book, Design Patterns: Elements of Reusable Object-Oriented Software, is: "One or more observers are interested in the state of a subject and register their interest with the subject by attaching themselves.
When something changes in our subject that the observer may be interested in, a notify message is sent which calls the update method in each observer. When the observer is no longer interested in the subject's state, they can simply detach themselves.
The update functionality here will be overwritten later with custom behaviour.
See below for inline comments on what these components do in the context of our example. Whilst very similar, there are differences between these patterns worth noting.
The Observer pattern requires that the observer or object wishing to receive topic notifications must subscribe this interest to the object firing the event the subject.
This event system allows code to define application specific events which can pass custom arguments containing values needed by the subscriber.
The idea here is to avoid dependencies between the subscriber and publisher. This differs from the Observer pattern as it allows any subscriber implementing an appropriate event handler to register for and receive topic notifications broadcast by the publisher. How are you doing today? Rather than single objects calling on the methods of other objects directly, they instead subscribe to a specific task or activity of another object and are notified when it occurs.
They also help us identify what layers containing direct relationships which could instead be replaced with sets of subjects and observers. This effectively could be used to break down an application into smaller, more loosely coupled blocks to improve code management and potentials for re-use.
Further motivation behind using the Observer pattern is where we need to maintain consistency between related objects without making classes tightly coupled. For example, when an object needs to be able to notify other objects without making assumptions regarding those objects. Dynamic relationships can exist between observers and subjects when using either pattern.
Lesson 4: Lesson 5: Lesson 6: Adjusting Fonts and Typography. Lesson 7: Decorating Pages with Color. Web page fit and finish The title test drive More photos for myPod Taking myPod for another test drive Reworking the site to use thumbnails Create the thumbnails Rework the HTML to use the thumbnails Take myPod for another test drive Turning the thumbnails into links Create individual pages for the photos So, how do I make links out of images?
To be transparent, or not to be transparent? That is the question Save the transparent PNG Wait, what is the color of the web page background?
Set the matte color Check out the logo with a matte Save the logo Add the logo to the myPod web page And now for the final test drive Chapter 6 Standards and All that Jazz: Calling all HTML professionals, grab the handbook What if we move the font up the family tree? Test drive your new CSS Overriding inheritance Test drive Adding an element to the greentea class Creating a class selector A greentea test drive Taking classes further Expanding Your Vocabulary Text and fonts from 30, feet What is a font family anyway?
How do I specify web colors? Let me count the ways Chapter 9 The Box Model: Getting Intimate with Elements The lounge gets an upgrade The new and improved, ultra-stylish lounge Setting up the new lounge Starting with a few simple upgrades A very quick test drive One more adjustment Checking out the new line height Getting ready for some major renovations A closer look at the box model What you can do to boxes Meanwhile, back at the lounge Are we there yet?
How do you increase the margin just on the right? A two-minute guide to borders Border fit and finish Congratulations!