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First Ajax Steps with jQuery

One of the most obvious client side features of any
Javascript client library is the ability to make AJAX calls to the server.
jQuery includes a host of Ajax functions that make it easy to retrieve content
from a Url starting with the low level and do-everything $.ajax() function
 plus a number of others that are simpler
and more focused to specific tasks. Here’s a list of some of the functions
available:

Step 0: Before You Get Started



• Just in case something goes wrong, make sure you have a backup. WordPress Backups is a comprehensive guide.
  
• Make sure the database user name registered to WordPress has permission to create, modify, and delete database tables. If you installed WordPress in the standard way, and nothing has changed since then, you are fine.
  
• Deactivate your plugins. A plugin might not be compatible with the new version, so it's nice to check for new versions of them and deactivate any that may cause problems. You can reactivate plugins one-by-one after the upgrade. This is particularly important when upgrading to WordPress 2.7!

Step 1: Replace WordPress files



1. Get the latest WordPress. Either download and extract it to your computer or download it directly to the server.
   
   1. As a reminder, to extract a tar.gz to a folder use this command, replacing (folder name) with the name of your folder: tar -xvzf latest.tar.gz -C ./(folder name)
      
   2. Delete your old wp-includes and wp-admin directories.
      
   3. Copy the new WordPress files to your server, overwriting old files in the root, except perhaps the wp-content folder (see "NOTE" below). You may use FTP or shell commands to do so. Note that this means *all* the files, including all the files in the root directory as well. If you use the default or classic theme and have customized it, then you can skip that theme.
      

Before You Start Writing




Before you start writing an article, ask the following questions:





1. How will I address the reader?
   
   (Reporter? Provider of information? Average man or woman?)
2. What pronoun and tense will I use?
   
   (Impersonal reportorial? Personal but formal? Personal and casual?)
3. What attitude will I take toward the material?
   
   (Involved? Detached? Judgmental? Ironic? Amused?)
4. How much of the subject do I want to cover?
5. Have I done enough research and/or have enough experience with the subject to write intelligently?
6. Is there anyone I can interview to gather more information on the subject and to quote? (See also: “Interviews”)
7. What is the one point I want to make?

Overloaded Methods

Sometimes it makes sense to have two different versions of the same method. For example, when we modified the PickNut method in the CoconutTree class to require a parameter that specified the number of nuts to pick, we lost the convenience of being able to pick a single nut by just calling PickNut(). C# actually lets you declare both versions of the method side by side and determines which one to use by the number and type of the parameters passed when the method is called. Methods that are declared with more than one version like this are called overloaded methods.

Constructors

A constructor is a special type of method that is invoked automatically when an object is created. Constructors allow you to specify starting values for properties, and other such initialization details.

At first glance, this looks just like a normal method. There are two differences, however:




• Constructors never return a value; thus, they don't have a return type (void, int, bool, etc.) in their declaration.
• Constructors have the same name as the class they are used to initialize. Since we are writing the Tree class, its constructor must also be named Tree.

C# Properties

Previously, we modified the PickNut method so that it would not accept too high a number, which would cause our CoconutTree to think it contained a negative number of coconuts. But there is a much simpler way to produce this unrealistic situation:

CoconutTree ct = new CoconutTree();        

ct.numNuts = -10;

How can we protect object fields like numNuts from being assigned values like this that don't make sense? The solution is to make the fields themselves private, and permit access to them using a C# Property.

Here are the access modifiers supported by C#:




• public: any code may access the class or class member.
• private: the class or class member is not accessible outside of the class that contains it (yes, in advanced cases, you can put a class inside another class).
• protected: the class or class member is only accessible by the class that contains it, or any subclass of that class.
• internal: the class or class member is only accessible by code in the same assembly (DLL).
• protected internal: the class or class member is accessible by code in the same assembly (DLL), or by any subclass of the class that contains it.



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If you don't specify any access modifier, C# will default to private.

11     Tree tree1 = new Tree();

As the comment on line 10 suggests, line 11 achieves the feat of creating a new Tree out of thin air. This is a really important line; so let me explain it in depth. The line begins by declaring the class (type) of object to be created (in this case, Tree). We then give a name to our new Tree (in this case, tree1). This is in fact identical to declaring a new variable by specifying the type of data it will contain followed by the name of the variable (e.g. string msg).

The rest of the line is where the real magic happens. The word new is a special C# keyword that triggers the instantiation of a new object. After new comes the name of the class to be instantiated, followed by a pair of parentheses (again, in more complex cases that we shall see later, these parentheses may not be empty).

In brief, this line says, "create a variable of type Tree called tree1, and assign it a value of a new Tree." So in fact this line isn't just creating a Tree, it's also creating a new variable to store it in.