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Initializing properties inline

You can initialize properties inline—that is, when you declare them—with default values, as shown here: 

class Person {
  var age:Number = 50;
  var name:String = "John Doe";
}

When you initialize properties inline the expression on the right side of an assignment must be a compile-time constant. That is, the expression cannot refer to anything that is set or defined at runtime. Compile-time constants include string literals, numbers, Boolean values, null, and undefined, as well as constructor functions for the following built-in classes: Array, Boolean, Number, Object, and String.

For example, the following class definition initializes several properties inline:

class CompileTimeTest {
  var foo:String = "my foo"; // OK
  var bar:Number = 5; // OK
  var bool:Boolean = true; // OK
  var name:String = new String("Jane"); // OK
  var who:String = foo; // OK, because 'foo' is a constant

  var whee:String = myFunc(); // error! not compile-time constant expression
  var lala:Number = whee; // error! not compile-time constant expression
  var star:Number = bar + 25; // OK, both 'bar' and '25' are constants

  function myFunc() {  
    return "Hello world";  
  }
}

This rule only applies to instance variables (variables that are copied into each instance of a class), not class variables (variables that belong to the class itself). For more information about these kinds of variables, see Instance and class members.

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