ptg 352 Chapter 14 ActionScript, just like any human language, has rules you should follow. However, in ActionScripts, you have to follow the rules or it won't work. One of the more important rules to follow is the use of dot syntax. The use of dots (.) in a script serves several pur- poses. First, is to specify the target path to a particular Timeline. For example, _root.amer- ica.kansas.wichita defines a movie clip on the main (_root) Timeline with the name america, containing a movie clip named kansas, which in turn contains a movie clip named wichita. Dot syntax is used to create a road map for Flash to follow. Dot syntax is a separator between two or more parts of a Flash script. Another use of dot syntax is to change the properties and methods for a specific object. Since ActionScript, by definition is an object- oriented language, Flash performs its respon- sibilities by instructing an object to do something (method), or by changing a prop- erty. For example, star._rotation = 90; instructs Flash to rotate the MovieClip instance named star , 90 degrees (property). To instruct the star MovieClip instance to play (method), you would enter the following code: star.play(); Using Dot Syntax Movie Clip with Instance Name: MovieA ActionScript 2.0 From the Library of Wow! eBook ptg Chapter 14 Using Basic ActionScripts 353 When you use ActionScripts, you have the ability to work with data. Data can be informa- tion entered in by a visitor in an input data field, or it can be computer information such as the current position of the mouse, or the date and time. When you work with data, you have 4 possible data types: ◆ String. Allows for the entering of text values. ◆ Number. Allows for the entering of numeric values. ◆ Boolean. A Boolean state has two values; typically true or false. ◆ Object. Serves as a storage device for any data type, including other objects. Use Data Types to Control Information Since data types control the type of informa- tion that can be entered into a data field, you can use them to validate the data someone is entering. For example, you want to create a calculator to convert between degrees Fahrenheit and Celsius. To do this, you will need an input field for someone to enter the current temperature in Fahrenheit, a button that would perform the calculation, and then a dynamic text field for the result, and one for an error message. Select the Input Field, and then give it a unique variable name in the Properties panel. Select the Error Dynamic Text Field and give it a unique variable name in the Properties panel. Select the Results Dynamic Text Field, and give it a unique variable name in the Properties panel. Select the button instance, and then enter a script into the Actions panel (see the example file for script details). When the movie is played, the visitor will enter a value into the data field, and it will be evaluated as to whether it's purely numeric. If it isn't, an error message will display in the dynamic error field. If the field contains num- bers, then the calculation will perform the conversion and display the results displayed in the output field. 4 3 2 1 Understanding Data Types Error Message using text Error Message using a blank field Correct data no error message From the Library of Wow! eBook ptg 354 Chapter 14 A function is a block of ActionScript code that can be reused anywhere in a SWF file. If you pass values as parameters to a function, the function will operate on those values. A func- tion can also return values. Flash contains built-in functions that let you access certain information and perform certain tasks, such as getting the version number of Flash Player hosting the SWF file (getVersion()). Functions that belong to an object are called methods. Functions that don't belong to an object are called top-level functions and are found in the Functions category of the Actions panel. Each function has its own characteristics, and some functions require you to pass cer- tain values. If you pass more parameters than the function requires, the extra values are ignored. If you don't pass a required parame- ter, the empty parameters are assigned the undefined data type, which can cause errors when you export a script. To call a function, it must be in a frame that the playhead has reached. To call a function, simply u s e the function name and pass any required parameters. The following code describes a common syntax for creating functions: function firstFunction (x, y, z) { // place all actions here; } Using Functions Calling a Function Functions begin with the word function, fol- lowed by the name of the function (user- defined). The area enclosed by parenthesis is used for passing parameters to the function actions. If the parameters are left blank, you're essentially creating a generic function that will function the same way every time it's called. If the function contains parameters, it will perform in a unique way each time it's called. When you call a function, you're instructing Flash to execute all of the actions within that function. Therefore, if firstFunction contained 20 actions, all of them would be executed by using a single line of script. To call a function, simply add this line to the action: myFunction (); Passing Parameters to a Function If the function has been defined to accept parameter information, you can use the fol- lowing line of script: myFunction (parameter 1, parameter2); Once a Function is defined, it can be called anytime it's needed. Therefore, it's a good practice to define all of your functions in frame 1 of the active Flash document. That way they can be called anytime after that. From the Library of Wow! eBook ptg Chapter 14 Using Basic ActionScripts 355 Conditional statements in ActionScript are a critical part of interactivity. They let you pro- gram a script based on any number of condi- tions. For example, in the morning, you say good day, or good morning to someone you meet. In doing so, you made a conditional choice. ActionScript does the same thing. You can create an ActionScript that checks the time of day. If it's before noon, Flash responds with a Good Morning message. If it's from noon to 5, Flash says Good Afternoon, or from 5 till mid- night, Flash says Good Evening. This type of condition is known as an if/else condition. If this happens, do this… else do that. Since a variable can be almost anything you can measure on a computer, and a conditional statement is made up of two or more vari- ables, ActionScript can be taken to a point where it almost thinks for itself. The previous example could be expressed in flow charting the following way: Typically, when you're creating a condi- tional statement, you're comparing one ele- ment against another using operators. The following operators are available to create conditional statements: ◆ == Checks for equality between two values (is time of day equal to 5). ◆ != Checks for inequality between two values. ◆ < Checks for less than (is value A less than value B). ◆ > Checks for greater than (is value A greater than value B). ◆ <= Checks for less than or equal to between two values. ◆ >= Checks for greater than or equal to between two values. ◆ && Checks for a logical AND (if day == "Friday" && time > 5). ◆ || Checks for a logical OR (if day == "Saturday" || day == "Sunday"). Using these operators to check between two or more values, you can create complex ActionScripts that react differently based on the available data. To create a dynamic field that checks the time, and responds with the appropriate answer, you would enter the fol- lowing code: if (time > "0000 && time < 1200) { response = "Good Morning"; } else if (time >1200 && time < 1700) { response = "Good Afternoon"; }else if (time > 1700 && time < 2400); response = "Good Evening" } Using Conditional Statements From the Library of Wow! eBook ptg 356 Chapter 14 Attaching a mouse event to a button is probably the easiest of all the event handlers. For example, you have a movie clip of a dog that con- tains a barking audio file. When the movie clip plays, the dog barks. The trick is to have the dog bark when the visitor rolls their mouse over the dog’s face. To do this, you will need to create an invisible button and then attach the mouse event to the invisible button. Attaching a Mouse Event to a Button Attach an Event to a Button Click the Insert menu, and then click New Symbol. Select the Button type, and then name the symbol. Click OK. Create a blank keyframe in the Hit state of the button, and then create a shape. Leave the Up, Over, and Down states blank. Exit the Symbol editing mode, and then return to the Stage. Drag a movie clip onto the Stage. Create a new layer, and then name the layer. Drag the invisible button onto the Stage, and then place it over the area of the image you want to use as a button. Enter the script (ActionScript 2.0) as shown in the illustration. ◆ ActionScript 3.0 example files are available on the Web at www.perspection.com . When the visitor rolls into or out of the invisible button, the rollOver or rollOut event handlers will trigger the playing or stopping of the dog movie clip. Click the Control menu, point to Test Movie, and then click Test. 10 9 8 7 6 5 4 3 2 1 7 8 9 6 3 2 From the Library of Wow! eBook ptg Chapter 14 Using Basic ActionScripts 357 Frame event handlers are easy to understand. When an action is attached to a frame, the action is triggered when the play head hits the frame. For example, you want to create a frame event that swaps images on the Stage, and you want the images to swap every 40 frames. You can attach an ActionScript that swaps the image, and place the action every 40 frames. When the play head hits the frame, the action executes. When you attach an ActionScript to a frame, you’ll need a blank keyframe on the Timeline, and it is strongly recommended that you always place ActionScripts in a separate layer from access and control. In addition, if you're planning to swap images in a Flash movie, it's always best to use a blank movie clip (called a placeholder) to hold the images. Working with Frame Events Attach an ActionScript to a Frame Drag a blank movie clip onto the Stage, and then select the clip. Give the movie clip a unique instance name in the Properties panel. Create a new layer, and then name the layer. Create blank keyframes at frame numbers 1, 21, 41, and 61. Select a frame, click the Insert menu, point to Timeline, and then click Blank Keyframe. Select frame 1, and then enter the script (ActionScript 2.0) as shown in the illustration. ◆ ActionScript 3.0 example files are available on the Web at www.perspection.com . Select frames 21, 41, and 61, and then repeat the script, except change the name of the image you want to load (image_b.jpg, image_c.jpg, image_d.jpg). Click the Control menu, point to Test Movie, and then click Test. 8 7 6 5 4 3 2 1 6 4 3 2 1 From the Library of Wow! eBook . syntax is used to create a road map for Flash to follow. Dot syntax is a separator between two or more parts of a Flash script. Another use of dot syntax. before noon, Flash responds with a Good Morning message. If it's from noon to 5, Flash says Good Afternoon, or from 5 till mid- night, Flash says