About data types 85
For example, the following code does not specify the data type of the parameter xParam. At
runtime, you use the parameter to hold a value of type Number and then a value of type
String. The dynamicTest() function then uses the typeof operator to test whether the
parameter is of type String or Number.
function dynamicTest(xParam) {
if (typeof(xParam) == "string") {
var myStr:String = xParam;
trace("String: " + myStr);
} else if (typeof(xParam) == "number") {
var myNum:Number = xParam;
trace("Number: " + myNum);
}
}
dynamicTest(100);
dynamicTest("one hundred");
You do not need to explicitly add data type information in your ActionScript. The
ActionScript compiler lets you use properties and invoke methods that do not exist at compile
time. This lets you create properties or assign dynamically methods at runtime.
An example of the flexibility afforded by dynamic type checking involves the use of properties
and methods that are not known at compile time. Because the code is less restrictive, it can
lead to benefits in some coding situations. For example, the following code creates a function
named
runtimeTest() that invokes a method and returns a property, neither of which is
known to the compiler. The code will not generate a compile-time error, but if the property or
method is not accessible at runtime, then a runtime error will occur.
function runtimeTest(myParam) {
myParam.someMethod();
return myParam.someProperty;
}
About determining data type
While testing and debugging your programs, you might discover problems that seem to be
related to the data types of different items. Or if you use variables that are not explicitly
associated with a data type, you might find it useful to know the data type of a given variable.
Using ActionScript, you can determine an item’s data type. You can use the
typeof operator
to return information about data.
Use the
typeof operator to get the data types, but remember that typeof does not return
information about the class to which an instance belongs.
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