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But I don't want to be a programmer!

• ActionScript for journalists
• Presentation by Mindy McAdams
• Flashjournalism.com

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Functions in scripting languages

• A function is a self-contained script that can be
  executed on demand, and which does not run until
  it is told to run
• Actions you have already seen such as stop()
  and play() can be contained inside a function

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Conventions of a function

• In Exercise 8.7, you see a typical function for
  the first time in this book (Synchronizing
  images to loaded audio)
• A typical ActionScript function looks like this
• function nameOfFunction()
• stuff here

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Using a function

• The function
• function nameOfFunction()
• stuff here
• Calling the function (later)
• nameOfFunction()
• When you call a function, whatever script is
  inside will be executed

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Choosing a name for a function

• The name of a function must not be any of the
  reserved words in ActionScript (see pp. 479-480)
• This is the reason why you see some strange names
  for functions, such as loadTheMovie because you
  cannot name a function load, or loadMovie
• ActionScript would be confused if you used a
  reserved word to name a function

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Similarity to other languages

• ActionScript is based on an international
  standard known as ECMAscript
• JavaScript is also based on ECMAscript
• ActionScript has many similarities to JavaScript,
  but they are NOT the same thing!
• Dont assume you can use terms from JavaScript
• Look up the ActionScript methods, etc., in the
  Flash Help files

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When to create a function

• You realize you will need to do the same thing
  more than once in the Flash movie
• The one function can be called many times
• A function can be called on a frame, or on a
  button

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Example of a function

• Say you want a function to pause a Sound object
  (stored in a variable named x)
• Write the function (once)
• function pauseMySound()
• p Math.floor(x.position/1000)
• x.stop
• Call the function (many times)
• pauseMySound()

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Define variables outside functions

• There are two variables in this function
• function pauseMySound()
• p Math.floor(x.position/1000)
• x.stop
• You must declare the variables BEFORE the
  function, and OUTSIDE of the
• var p 0
• var x new Sound()
• Remember A variable is declared (with var) only
  ONCE in a movie

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Passing a variable to a function

• If you want the function to be performed on
  different variables in different parts of your
  movie
• Write the function (once)
• function pauseMySound(theSound)
• p Math.floor(theSound.position/1000)
• theSound.stop
• Call the function (in this case, only for x)
• pauseMySound(x)

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Passing a variable (2)

• If you have something in parens here
• function pauseMySound(theSound)
• p Math.floor(theSound.position/1000)
• theSound.stop
• You MUST put an existing variable name in the
  parens when you call the function
• pauseMySound(x)

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NOT passing a variable

• If you have nothing in parens here
• function pauseMySound()
• p Math.floor(x.position/1000)
• x.stop
• You MUST NOT put anything in the parens when you
  call the function
• pauseMySound()

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Things we do with functions

• Test a condition (if then)
• Do something again and again until some condition
  is met
• Usually with a loop
• Or with onEnterFrame
• Or with setInterval

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Testing a condition

• The condition (if) is defined in parens for
  example
• if (x.getVolume() gt 0)
• The result (meaning then do this) is contained
  in curly braces
• x.setVolume(0)
• This says If the current volume of sound x is
  greater than zero, then set the volume of x to
  zero

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Testing a condition (2)

• The function
• function volumeToZero()
• if (x.getVolume() gt 0)
• x.setVolume(0)
• This says If the current volume of sound x is
  greater than zero, then set the volume of x to
  zero

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Adding else to a condition

• function changeMyVolume ()
• if (x.getVolume() gt 0)
• x.setVolume(0)
• else
• x.setVolume(100)
• This says If the current volume of sound x is
  greater than zero, then set the volume of x to
  zero otherwise, set the volume of x to 100

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Running a for loop

• There are different kinds of loops in scripting
  a for loop is very common
• The beginning of a for loop
• for (i0 ilt7 i) stuff
• This means
• The initial value of i is zero
• For as long as i is less than or equal to 7
• Increment i (that is, add 1 to i)
• The initial value of i can be anything
• The condition can be anything
• You can decrement or increment i

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Use of onEnterFrame

• Explained in the book, pp. 213-214, and in
  Exercise 10.5, Step 6
• If you use _root.onEnterFrame --
• You must eventually stop or cancel it (otherwise,
  disaster!)
• delete _root.onEnterFrame
• Never try to use two simultaneous instances of
  _root.onEnterFrame

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Use of setInterval

• Explained in the book, Exercise 10.7, Step 9
• If you use setInterval --
• You must eventually stop or cancel it (otherwise,
  disaster!)
• To stop a setInterval you must first name the
  interval this means you CAN run two or more
  setIntervals at the same time

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Naming and clearing setInterval

• Say you have created a function named
  changePhoto
• To use setInterval with that function
• timer setInterval(changePhoto, 3000)
• You have named the interval timer
• To stop this setInterval --
• clearInterval(timer)

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What does setInterval do?

• Use it to determine how often a function will
  execute
• timer setInterval(changePhoto, 3000)
• 3000 is 3 seconds
• Usually we combine setInterval with a condition,
  e.g., If we have shown fewer than 10 photos,
  then show a new photo after 3 seconds have passed

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The End

• Presentation by Mindy McAdams
• Flashjournalism.com