Object

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The root class that every class must inherit from

R.oo Class Object public class Object Object is the root class of all other classes. All classes must extends this class, directly or indirectly, which means that they all will inherit the methods in this class.

Keywords
classes, methods, programming
Usage
Object(core=NA)
Arguments
core
The core value of each reference referering to the Object. By default, this is just the smallest possible Robject, but there are situations where it is useful to have another kind of core, which is the case with the Class class.
Fields and Methods

Methods: rll{ $ Makes the fields and methods of an Object accessable via the $ and the [[ operator. $<- Makes the fields and methods of an Object assignable via the $<- and the [[<- operator. [[ - [[<- - as.character Gets a character string representing the object. attach Attach an Object to the Rsearch path. clone Clones an Object. detach Detach an Object from the Rsearch path. equals Compares an object with another. extend Extends another class. finalize Finalizer methods called when object is clean out. getFields Returns the field names of an Object. getInstanciationTime Gets the time when the object was instanciated. getStaticInstance Gets the static instance of this objects class. hasField Checks if a field exists or not. hashCode Gets a hash code for the Object. ll Generates a list of informative properties of all members of an Object. load Static method to load an Object from a file or a connection. objectSize Gets the size of the Object in bytes. print Prints an Object. save Saves an Object to a file or a connection. }

References

[1] Henrik Bengtsson, The R.oo package - Object-Oriented Programming with References Using Standard R Code, In Kurt Hornik, Friedrich Leisch and Achim Zeileis, editors, Proceedings of the 3rd International Workshop on Distributed Statistical Computing (DSC 2003), March 20-22, Vienna, Austria. http://www.ci.tuwien.ac.at/Conferences/DSC-2003/Proceedings/

Aliases
  • Object
Examples
#########################################################################
# Defines the class Person with private fields .name and .age, and
# with methods print(), getName(), setName(), getAge() and setAge().
#########################################################################
setConstructorS3("Person", function(name, age) {
  if (missing(name)) name <- NA;
  if (missing(age))  age <- NA;

  extend(Object(), "Person",
    .name=name,
    .age=age
  )
})


setMethodS3("as.character", "Person", function(this) {
  paste(this$.name, "is", as.integer(this$.age), "years old.");
})

setMethodS3("equals", "Person", function(this, obj) {
  ( identical(data.class(this), data.class(obj)) &&
    identical(this$getName(), obj$getName()) &&
    identical(this$getAge() , obj$getAge() )    );
})

setMethodS3("hashCode", "Person", function(this) {
  # Get the hashCode() of the '.name' and the '.age' fields
  # using hashCode.default().
  hashCode(this$.name) * hashCode(this$.age);
})

setMethodS3("getName", "Person", function(this) {
  this$.name;
})

setMethodS3("setName", "Person", function(this, newName) {
  throw("It is not possible to change the name of a Person.");
})

setMethodS3("getAge", "Person", function(this) {
  this$.age;
})

setMethodS3("setAge", "Person", function(this, newAge) {
  if (!is.numeric(newAge))
    throw("Age must be numeric: ", newAge);
  if (newAge < 0)
    throw("Trying to set a negative age: ", newAge);
  this$.age <- newAge;
})




#########################################################################
# Code demonstrating different properties of the Object class using
# the example class Person.
#########################################################################

# Create an object (instance of) the class Person.
p1 <- Person("Dalai Lama", 67)

# 'p1' is an Object of class Person.
print(data.class(p1))  # "Person"

# Prints information about the Person object.
print(p1)            # "Dalai Lama is 67 years old."

# or equivalent (except that no generic method has to exist):

p1$print()           # "Dalai Lama is 67 years old."

# Shows that no generic method is required if the \$ operator is used:
print(p1$getName())  # "Dalai Lama"

# The following will call p1$getName() since there exists a get-()
# method for the 'name' property.
print(p1$name)       # "Dalai Lama"

# and equivalent when using the [[ operator.
print(p1[["name"]])  # "Dalai Lama"

# The following shows that p1$setName(68) is called, simply because
# there exists a set-() method for the 'name' property.
p1$age <- 68         # Will call p1$setAge(68)

# Shows that the age of the Person has been updated:
print(p1)            # "Dalai Lama is 68 years old."

# If there would not exists such a set-() method or field a new
# field would be created:
p1$country <- "Tibet"

# Lists all (non-private) members of the Person object:
print(ll(p1))

# which gives
#      member class      mode    typeof length  dim bytes
#   1 country  NULL character character      1 NULL    44

# The following will call p1$setName("Lalai Dama") which will
# throw an exception saying one can not change the name of
# a Person.
tryCatch(p1$name <- "Lalai Dama", error=print)

# The following will call p1$setAge(-4) which will throw an
# exception saying that the age must be a non-negative number.
tryCatch(p1$age <- -100, error=print)

# Attaches Object 'p1' to the search path.
attach(p1)

# Accesses the newly created field 'country'.
print(country)       # "Tibet"

# Detaches Object 'p1' from the search path. Note that all
# modifications to 'country' are lost.
country <- "Sweden"
detach(p1)
print(p1$country)    # "Tibet"


# Saves the Person object to a tempory file.
filename <- tempfile("R.methodsS3.example")
save(p1, filename)

# Deletes the object
rm(p1)

# Loads an Object (of "unknown" class) from file using the
# static method load() of class Object.
obj <- Object$load(filename)

# Prints information about the new Object.
print(obj)

# Lists all (non-private) members of the new Object.
print(ll(obj))
Documentation reproduced from package R.oo, version 1.0.3, License: GPL version 2 or newer

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