NSResponder

Inherits From: NSObject

Conforms To: NSCoding NSObject (NSObject)

Declared In: AppKit/NSResponder.h

Class Description

NSResponder is an abstract class that forms the basis of command and event processing in the Application Kit. Most Application Kit classes inherit from NSResponder. When an NSResponder receives an event or action message that it can't respond tothat it doesn't have a method forthe message is sent to its next responder. For an NSView, the next responder is usually its superview; the content view's next responder is the NSWindow. Each NSWindow, therefore, has its own responder chain. Messages are passed up the chain until they reach an object that can respond.

Action messages and keyboard event messages are sent first to the first responder, the object that displays the current selection and is expected to handle most user actions within a window. Each NSWindow has its own first responder. Messages the first responder can't handle work their way up the responder chain.

This class defines the methods that pass event and action messages along the responder chain.

Managing the Next Responder

• - (NSResponder *)nextResponder Returns the receiver's next responder.
• - (void)setNextResponder:(NSResponder *)aResponder Makes aResponder the receiver's next responder.

• - (BOOL)acceptsFirstResponder Subclasses override to accept or reject first responder status. NSResponder's implementation simply returns NO.
• - (BOOL)becomeFirstResponder Notifies the receiver that it's the first responder.
• - (BOOL)resignFirstResponder Notifies the receiver that it's not the first responder.

• - (BOOL)performKeyEquivalent:(NSEvent *)theEvent Subclasses override to respond to keyboard input. NSResponder's implementation simply returns NO to indicate theEvent isn't handled.
• - (BOOL)tryToPerform:(SEL)anAction Aids in dispatching action messages. Returns YES if an with:(id)anObject responder in the responder chain can perform the anAction method, which takes the single argument anObject.

• - (void)flagsChanged:(NSEvent *)theEvent Subclasses override to handle flags-changed events. NSResponder's implementation passes the message to the receiver's next responder.
• - (void)helpRequested:(NSEvent *)theEvent Causes the Help panel to display the help attached to the receiver. If there's no attached help, passes the message to the receiver's next responder.
• - (void)keyDown:(NSEvent *)theEvent Subclasses override to handle key-down events. NSResponder's implementation passes the message to the receiver's next responder. If the first responder changes, this method posts the notification NSTextDidEndEditingNotification with the current object and, in the notification's dictionary, the key NSTextMovement to the default notification center.
• - (void)keyUp:(NSEvent *)theEvent Subclasses override to handle key-up events. NSResponder's implementation passes the message to the receiver's next responder.
• - (void)mouseDown:(NSEvent *)theEvent Subclasses override to handle mouse-down events. NSResponder's implementation passes the message to the receiver's next responder.
• - (void)mouseDragged:(NSEvent *)theEvent Subclasses override to handle mouse-dragged events. NSResponder's implementation passes the message to the receiver's next responder.
• - (void)mouseEntered:(NSEvent *)theEvent Subclasses override to handle mouse-entered events. NSResponder's implementation passes the message to the receiver's next responder.
• - (void)mouseExited:(NSEvent *)theEvent Subclasses override to handle mouse-exited events. NSResponder's implementation passes the message to the receiver's next responder.
• - (void)mouseMoved:(NSEvent *)theEvent Subclasses override to handle mouse-moved events. NSResponder's implementation passes the message to the receiver's next responder.
• - (void)mouseUp:(NSEvent *)theEvent Subclasses override to handle mouse-up events. NSResponder's implementation passes the message to the receiver's next responder.
• - (void)noResponderFor:(SEL)eventSelector Responds to an event message that has reached the end of the responder chain without finding an object that can respond. When the event is a key down, generates a beep.
• - (void)rightMouseDown:(NSEvent *)theEvent Subclasses override to handle right mouse-down events. NSResponder's implementation passes the message to the receiver's next responder.
• - (void)rightMouseDragged:(NSEvent *)theEvent Subclasses override to handle right mouse-dragged events. NSResponder's implementation passes the message to the receiver's next responder.
• - (void)rightMouseUp:(NSEvent *)theEvent Subclasses override to handle right mouse-up events. NSResponder's implementation passes the message to the receiver's next responder.

• - (id)validRequestorForSendType:(NSString *)typeSent returnType:(NSString *)typeReturned Subclasses override to determine which Services menu items are enabled at a given time. Returning self enables services that can receive typeSent pasteboard types and can return typeReturned pasteboard types. Returning nil disables them. NSResponder's implementation passes the message to the receiver's next responder.