These public methods are in the Object class, the base class for Ruby. This documentation is adapted and abbreviated from http://www.ruby-doc.org/core/classes/Object.html, where you can find code examples and longer explanations. Object includes the Kernel module, whose methods are listed in the next section.
obj == other [or] obj.equal?(other) [or] obj.eql?(other)At the Object level, == returns true only if obj and other are the same object. Typically, this method is overridden in descendant classes to provide class-specific meaning. Unlike ==, the equal? method should never be overridden by subclasses: it is used to determine object identity (that is, a.equal?(b) if and only if a is the same object as b). The eql? method returns true if obj and other have the same value.
obj === otherFor class Object, effectively the same as calling ==, but typically overridden by descendants to provide meaningful semantics in case statements.
obj =˜ otherOverridden by descendants (notably Regexp and String) to provide meaningful pattern-match semantics.
obj._ _id_ _ [or] obj.object_idReturns an integer identifier for obj. The same number will be returned on all calls to id for a given object, and no two active objects will share an id. Object#object_id is a different concept from the :name notation, which returns the symbol id of name. Replaces the deprecated Object#id.
obj.classReturns the class of obj, now preferred over Object#type, because an object's type in Ruby is only loosely tied to that object's class. This method must always be called with an explicit receiver, because class is also a reserved word in Ruby.
obj.cloneProduces a shallow copy of obj—the instance variables of obj are copied, but not the objects they reference. Copies the frozen and tainted state of obj. See also the discussion under Object#dup.
obj.display(port=$>)Prints obj on the given port (default $>).
obj.dupProduces a shallow copy of obj—the instance variables of obj are copied, but not the objects they reference. dup copies the tainted state of obj.
obj.equal?(other) [or] obj.eql?(other) [or] obj == otherSee ==.
obj.eql?(other) [or] obj == other [or] obj.equal?(other)See ==.
obj.extend(module, . . . )Adds to obj the instance methods from each module given as a parameter.
obj.freezePrevents further modifications to obj. A TypeError will be raised if modification is attempted. There is no way to unfreeze a frozen object. See also Object#frozen?.
obj.frozen?Returns the freeze status of obj.
obj.hashGenerates a Fixnum hash value for this object.
obj.idSoon-to-be deprecated version of Object#object_id.
obj.inspectReturns a string containing a human-readable representation of obj. If not overridden, uses the to_s method to generate the string.
obj.instance_eval(string [, filename [, lineno]]) [or] obj.instance_eval { | | block }Evaluates a string containing Ruby source code, or the given block, within the context of the receiver (obj). In order to set the context, the variable self is set to obj while the code is executing, giving the code access to obj's instance variables. In the version of instance_eval that takes a string, the optional second and third parameters supply a filename and starting line number lineno that are used when reporting compilation errors.
obj.instance_of?(class)Returns true if obj is an instance of the given class. See also Object#kind_of?.
obj.instance_variable_defined?(symbol)Returns true if the given instance variable is defined in obj.
obj.instance_variable_get(symbol)Returns the value of the given instance variable, or nil if the instance variable is not set.
obj.instance_variable_set(symbol, obj)Sets the instance variable named by symbol to object, thereby frustrating the efforts of the class's author to attempt to provide proper encapsulation. The variable did not have to exist prior to this call.
obj.instance_variablesReturns an array of instance variable names for the receiver.
obj.is_a?(class) [or] obj.kind_of?(class)Returns true if class is the class of obj, or if class is one of the superclasses of obj or modules included in obj.
obj.method(sym)Looks up the named method as a receiver in obj, returning a Method object (or raising NameError). The Method object acts as a closure in obj's object instance, so instance variables and the value of self remain available.
obj.methodsReturns a list of the names of methods publicly accessible in obj. This will include all the methods accessible in the ancestors of obj.
obj.nil? [or] nil.nil? [or] anything_else.nil?Returns true if receiver is nil. Only the object nil responds true to nil?.
obj.private_methods(all=true)Returns the list of private methods accessible to obj. If the all parameter is set to false, only those methods in the receiver will be listed.
obj.protected_methods(all=true)Returns the list of protected methods accessible to obj. If the all parameter is set to false, only those methods in the receiver will be listed.
obj.public_methods(all=true)Returns the list of public methods accessible to obj. If the all parameter is set to false, only those methods in the receiver will be listed.
obj.remove_instance_variable(symbol)Removes the named instance variable from obj, returning that variable's value.
obj.respond_to?(symbol, include_private=false)Returns true if obj responds to the given method. Private methods are included in the search only if the optional second parameter evaluates to true.
obj.send(symbol [, args . . . ]) [or]obj._ _send_ _(symbol [, args . . . ])Invokes the method identified by symbol, passing it any arguments specified. You can use _ _send_ _ if the name send clashes with an existing method in obj.
obj.singleton_method_added(symbol)Invoked as a callback whenever a singleton method is added to the receiver.
obj.singleton_method_removed(symbol)Invoked as a callback whenever a singleton method is removed from the receiver.
obj.singleton_method_undefined(symbol)Invoked as a callback whenever a singleton method is undefined in the receiver.
obj.singleton_methods(all=true)Returns an array of the names of singleton methods for obj. If the optional all parameter is true, the list will include methods in modules included in obj.
obj.taintMarks obj as tainted—if the $SAFE level is set appropriately, many method calls which might alter the running program's environment will refuse to accept tainted strings.
obj.tainted?Returns true if the object is tainted.
obj.to_aReturns an array representation of obj. For objects of class Object and others that don't explicitly override the method, the return value is an array containing self. However, this latter behavior will soon be obsolete.
obj.to_enum(method = :each, *args) [or] obj.enum_for(method = :each, *args)Returns Enumerable::Enumerator.new(self, method, *args).
obj.to_sReturns a string representing obj. The default to_s prints the object's class and an encoding of the object id. As a special case, the top-level object that is the initial execution context of Ruby programs returns main.
obj.typeDeprecated synonym for Object#class.
obj.untaintRemoves the taint from obj.