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Object

The super class of all the Ruby class hierarchy, except for Kernel and Nil.

SuperClass:

Kernel

Methods:

self == other

Checks if two objects are same. The default definition in the Kernel class checks by object ID. It should be redefined in subclasses according to the characteristic of the class.

clone
dup

Returns the copy of the object. For cloned object,

obj == obj.clone
is always true, though
obj.equal?(obj.clone)
is false most of the time.

eql?(other)

Checks if two objects are same. This method is used by Hash to compare whether two keys are same. When this method is redefined, the hash method should be updated.

The default definition of the method eql? is like blow:

def eql?(other)
  self == other
end

equal?(other)

Checks if two objects have same object ID. This method should not be redefined in the subclass.

self === other

This method is used to compare in case. The default definitions is `=='.

extend(module...)

Extends self by adding methods defined in modules as singleton-methods.

hash

Returns the integer hash value of the object. It is used in the Hash class to calculate the holding place of an object. The hash value of two objects must be same, where these two objects are equal by using eql? operator. So, whenever you redefine the definition of the eql? operator in any class, don't forget to redefine hash method according to the definition.

id

Returns the unique integer value for each object.

inspect

Returns the human-readable string representation of the receiver.

initialize(...)

The initialize method for the user-defined classes. This method will be called from Class#new to initialize the newly created object. The default behavior is to do nothing. It is assumed that this method will be redefined in the subclasses. The argument to Class#new will be passed to the initialize

instance_of?(class)

Returns TRUE, if self is an instance of the specified class. It is always true, when obj.kind_of?(c) is true.

kind_of?(class)
is_a?(class)

Returns TRUE, if self is an instance of the specified class, or its subclass.

method_missing(msg_id, ...)

Will be called when the specified method is not defined for the receiver. The first argument, msg_id is the method name as a symbol. The second and later arguments are the arguments given to the undefined method, if any.

nil?

Checks whether the receiver is nil or not.

respond_to?(mesg[,priv])

Returns true if the receiver has the public method named mesg. Mesg must be the symbol fixnum or the string. It returns true for private methods, if the optional argument priv given, and its value is true,

type

Returns the name of the receiver's class.

send(symbol[, args...])

calls the method specified by the symbol, with args.

to_s

Returns the string representation of the self. This method is used internally by print and sprintf.

to_a

Converts the self into an array. Returns an array of 1 element contains self for classes would not be converted into an array naturally.


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