ExtendScript reflection interface

ExtendScript provides a reflection interface that allows you to find out everything about an object, including its name, a description, the expected data type for properties, the arguments and return value for methods, and any default values or limitations to the input values.

Reflection object

Every object has a reflect property that returns a reflection object that reports the contents of the object. You can, for example, show the values of all the properties of an object with code like this:

var f = new File ("myfile");
var props = f.reflect.properties;
for (var i = 0; i < props.length; i++) {
  $.writeln('this property ' + props[i].name + ' is ' + f[props[i].name]);
}

Reflection object properties

All properties are read only.

description String Short text describing the reflected object, or undefined if no description is available.
help String Longer text describing the reflected object more completely, or undefined if no description is available.
methods Array of ReflectionInfo An Array of ReflectionInfo object containing all methods of the reflected object, defined in the class or in the specific instance.
name String The class name of the reflected object.
properties Array of ReflectionInfo An Array of ReflectionInfo object containing all properties of the reflected object, defined in the class or in the specific instance. For objects with dynamic properties (defined at runtime) the list contains only those dynamic properties that have already been accessed by the script. For example, in an object wrapping an HTML tag, the names of the HTML attributes are determined at run time.

Reflection object functions

find()

reflectionObj.find (name)

name The property for which to retrieve information.

Returns the ReflectionInfo object for the named property of the reflected object, or null if no such property exists.

Use this method to get information about dynamic properties that have not yet been accessed, but that are known to exist.

Examples

This code determines the class name of an object:

obj = new String ("hi");
obj.reflect.name; // => String

This code gets a list of all methods:

obj = new String ("hi");
obj.reflect.methods; //=> indexOf,slice,...
obj.reflect.find ("indexOf"); // => the method info

This code gets a list of properties:

Math.reflect.properties; //=> PI,LOG10,...

This code gets the data type of a property:

Math.reflect.find ("PI").type; // => number

ReflectionInfo object

This object contains information about a property, a method, or a method argument. You can access ReflectionInfo objects in a Reflection object’s properties and methods arrays, by name or index:

obj = new String ("hi");
obj.reflect.methods[0];
obj.reflect.methods["indexOf"];

You can access the ReflectionInfo objects for the arguments of a method in the arguments array of the ReflectionInfo object for the method, by index:

obj.reflect.methods["indexOf"].arguments[0];
obj.reflect.methods.indexOf.arguments[0];

ReflectionInfo object properties

arguments Array of ReflectionInfo For a reflected method, an array of ReflectionInfo objects describing each method argument.
dataType String

The data type of the reflected element. One of:

  • boolean

  • number

  • string

  • Classname: The class name of an object.

    Note

    Class names start with a capital letter. Thus, the value string stands for a JavaScript string, while String is a JavaScript String wrapper object.

  • *: Any type. This is the default.

  • null

  • undefined: Return data type for a function that does not return any value.

  • unknown

defaultValue any The default value for a reflected property or method argument, or undefined if there is no default value, if the property is undefined, or if the element is a method.
description String Short text describing the reflected object, or undefined if no description is available.
help String Longer text describing the reflected object more completely, or undefined if no description is available.
isCollection Boolean When true, the reflected property or method returns a collection; otherwise, false.
max Number The maximum numeric value for the reflected element, or undefined if there is no maximum or if the element is a method.
min Number The minimum numeric value for the reflected element, or undefined if there is no minimum or if the element is a method.
name String Number The name of the reflected element. A string, or a number for an array index.
type String

The type of the reflected element. One of:

  • readonly: A Read only property.
  • readwrite: A read-write property.
  • createonly: A property that is valid only during creation of an object.
  • method: A method.