WebScripting is an informal protocol that defines methods that classes can implement to export their interfaces to a WebScript environment such as JavaScript.


Not all properties and methods are exported to JavaScript by default. The object needs to implement the class methods described below to specify the properties and methods to export. Furthermore, a method is not exported if its return type and all its parameters are not Objective-C objects or scalars.

Method argument and return types that are Objective-C objects will be converted to appropriate types for the scripting environment. For example:

  • nil is converted to undefined.

  • NSNumber objects will be converted to JavaScript numbers.

  • NSString objects will be converted to JavaScript strings.

  • NSArray objects will be mapped to special read-only arrays.

  • NSNull will be converted to JavaScript’s null.

  • WebUndefined will be converted to undefined.

  • WebScriptObject instances will be unwrapped for the scripting environment.

Instances of all other classes will be wrapped before being passed to the script, and unwrapped as they return to Objective-C. Primitive types such as int and char are cast to a numeric in JavaScript.

Access to an object’s attributes, such as instance variables, is managed by key-value coding (KVC). The KVC methods setValue:forKey: and valueForKey: are used to access the attributes of an object from the scripting environment. Additionally, the scripting environment can attempt any number of attribute requests or method invocations that are not exported by your class. You can manage these requests by overriding the setValue:forUndefinedKey: and valueForUndefinedKey: methods from the key-value coding protocol.

Exceptions can be raised from the scripting environment by sending a throwException(_:) message to the relevant WebScriptObject instance. The method raising the exception must be within the scope of the script invocation.


Getting attributes

class func webScriptName(forKey: UnsafePointer<Int8>!) -> String!

Returns the scripting environment name for an attribute specified by a key.

class func webScriptName(for: Selector!) -> String!

Returns the scripting environment name for a selector.

class func isSelectorExcluded(fromWebScript: Selector!) -> Bool

Returns whether a selector should be hidden from the scripting environment.

class func isKeyExcluded(fromWebScript: UnsafePointer<Int8>!) -> Bool

Returns whether a key should be hidden from the scripting environment.

Invoking methods

func invokeDefaultMethod(withArguments: [Any]!) -> Any!

Executes when a script attempts to invoke a method on an exposed object directly.

func invokeUndefinedMethod(fromWebScript: String!, withArguments: [Any]!) -> Any!

Handles undefined method invocation from the scripting environment.


func finalizeForWebScript()

Performs cleanup when the scripting environment is reset.

See Also

Incorporating Scripts (Legacy)

class WebScriptObject

A WebScriptObject object is an Objective-C wrapper for a scripting object passed to your application from the scripting environment.

class WebUndefined

WebUndefined objects are simply used to represent the JavaScript “undefined” value in methods when bridging between JavaScript and Objective-C. For example, if you invoke a JavaScript function that returns the JavaScript “undefined” value, then a WebUndefined object is returned to the Objective-C calling context.