Flex Certification in 50 Days

• ActionScript 3.0 is compliant with ECMA-262 specification & leverages parts of ECMAScript edition 4 spec
• There are 3 tiers of ActionScript APIs

• Ways ActionScript could be used in Flex

1. Inline within MXML tags
2. Nested within MXML tags
3. In MXML scripts
4. Within ActionScript classes

• Since ActionScript may use special characters otherwise interpreted by MXML compiler, we use CDATA block

	<mx:Script>
		<![CDATA [
		-----
		- - - - 
		]]>
	</mx:Script>

• ActionScript class files are text files that use the file extension .as
• MXML gets converted into ActionScript during compilation
• MXML tag === equivalent to === creating a component instance.

	<mx:Button id="button"/> === var button:Button = new Button();

• MXML component tags correspond to ActionScript classes
• MXML document themselves are essentially ActionScript classes
• An Application document is a class that extends mx.core.Application
• Code within MXML script === placing code in the class body
• Variable declaration within MXML scripts === properties of class
• Function within MXML scripts === methods of class
• Packages groups together classes so that you can ensure uniqueness of scope.

• ActionScript allows you to reference a class by the shorthand notation if you first add an import statement
• ActionScript class consists of -

Class Package declaration
Class declaration

• Each ActionScript class must be defined in it’s own file.
• Name of the file should be same as class name
• A package name in ActionScript corresponds to the directory structure within which the file is stored
• Class names start with a capital letter by ‘Convention’
• It’s possible to declare a variable without a datatype. (Remember Javascript?)
• Flex applications provide both runtime & compile time type checking
• Variables defined within a function inside a class are ONLY available within the function
• Variables defined in a  class but outside any functions become properties of that class. They are available throughout the class
• Access Modifiers

• In addition to this we also have ’static’ modifier which says that a property is directly accessible from the class rather than the instances.