The NIO::Monitor class monitors a specific IO object and lets you introspect on why that object was selected. Monitors are returned by Selectors whenever you #register an IO object or whenever they #select as ready for a particular interests.

NIO::Monitors are thread safe only if you are holding the selector lock (i.e. if you're in a block passed to #select). Don't share them between multiple threads unless only one thread at a time is calling #select.

The following methods are available for manipulating and inspecting interests:

• #interests: what this monitor is interested in (:r, :w, or :rw)
• #interests=: change the current interests for a monitor (to :r, :w, or :rw)
• #add_interest: add an interest to the current interest set
• #remove_interest: remove an interest from the current interest set
• #readiness: what I/O operations the monitored object is ready for
• #readable?: was the IO readable last time it was selected?
• #writable?: was the IO writable last time it was selected?

Monitors also support a #value and #value= accessor for storing a handle to an arbitrary object of your choice (e.g. a proc with a callback to fire on a given event)

• NIO::Monitor YARD Documentation