Chapter11.Statements and Expressions

Chapter 11. Statements and Expressions


  • Statement Syntax

  • Object Statements

  • Flow Modifiers

This chapter covers statements and expressions. Even though we have not formally gone over statements, you have already used them. A statement is simply a small piece of code made up of keywords, operators, and identifiers. Statements can be in one of six categories:

  • Declaration statements These statements involve declaring variables, creating functions, setting properties, declaring arrays, and so on. Here's an example:

     var myVariable:String;             // declares a variable myObject._x = 235;            //setting the horizontal position var my_array:Array = new Array ();//creating an array function myFunction (){        //creates a function 

  • Expressions These include any type of legal expression. Here's an example:

     i++;                      //increase a variable lName + space + fName;    //combining variables 

  • Flow modifiers These include any statement that disrupts the natural flow of the interpreter reading the ActionScript. There are two subtypes of flow modifiers: conditional statements and loop statements.

    Conditional statements use Boolean answers to determine what to do next or what not to do next. Here's an example:

     if (inputName == userName){       if (inputPassword == password){             gotoAndPlay("startPage");      }else {                displayMessage = "Double check your password";      } }else if (inputName != userName){           if (inputPassword == password){                 displayMessage = "Double check your user name";           } }else{      displayMessage = "Double check your all your information"; } 

    Loop statements run until a defined condition has been met. Here's an example where the trace function will be run while i is less than 30:

     for (var i:Number=0; i<30; i++) {      trace (i); } //output: (numbers 0-29) 

  • Predefined functions Functions that are predefined in ActionScript. Here's an example:

     trace ("function");              //a simple trace function gotoAndStop (2);                 //a playback function getProperty( myMovie, _x );      //gets the horizontal position 

  • Object statements Statements that deal with and manipulate objects. Here's an example:

     var myGrades:Object = { tests: 85, quizzes: 88, homework: 72 }; for (name in myGrades) {      trace ("myGrades." + name + " = " + myGrades[name]); } //output: myGrades.tests = 85 //        myGrades.quizzes = 88 //        myGrades.homework = 72 

  • Comments This last category is one of a kind. It includes comments used in code merely as information for the user while in the Actions panel. The interpreter will skip over these comments. Here's an example:

     //this is a comment used in ActionScript; /*this is a comment block */ 

Breaking up statements into these simple categories is done only to help you understand the different types and uses of statements. We will go over a few of these categories in more detail later in this chapter.

Now let's look at some of the basics of building these statements.

Macromedia Flash Professional 8 Unleashed
Macromedia Flash Professional 8 Unleashed
ISBN: 0672327619
EAN: 2147483647
Year: 2005
Pages: 319 © 2008-2017.
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