getClass               package:methods               R Documentation

_G_e_t _C_l_a_s_s _D_e_f_i_n_i_t_i_o_n

_D_e_s_c_r_i_p_t_i_o_n:

     Get the definition of a class.

_U_s_a_g_e:

     getClass(Class, .Force = FALSE, where)
     getClassDef(Class, where, package)

_A_r_g_u_m_e_n_t_s:

   Class: the character-string name of the class.

  .Force: if 'TRUE', return 'NULL' if the class is undefined;
          otherwise, an undefined class results in an error.

   where: environment from which to begin the search for the
          definition; by default, start at the top-level (global)
          environment and proceed through the search list.

 package: the name of the package asserted to hold the definition. 
          Supplied instead of 'where', with the distinction that the
          package need not be currently attached.

_D_e_t_a_i_l_s:

     A call to 'getClass' returns the complete definition of the class
     supplied as a string, including all slots, etc. in classes that
     this class extends.  A call to 'getClassDef' returns the
     definition of the class from the environment 'where', unadorned. 
     It's usually 'getClass' you want.

     If you really want to know whether a class is formally defined,
     call 'isClass'.

_V_a_l_u_e:

     The object defining the class.  This is an object of class
     '"classRepEnvironment"'.  However, _do not_ deal with the contents
     of the object directly unless you are very sure you know what
     you're doing.  Even then, it is nearly always better practice to
     use functions such as 'setClass' and 'setIs'. Messing up a class
     object will cause great confusion.

_R_e_f_e_r_e_n_c_e_s:

     The R package 'methods' implements, with a few exceptions, the
     programming interface for classes and methods in the book
     _Programming with Data_ (John M. Chambers, Springer, 1998), in
     particular sections 1.6, 2.7, 2.8, and chapters 7 and 8.

     While the programming interface for the methods package follows
     the reference, the R software is an original implementation, so
     details in the reference that reflect the S4 implementation may
     appear differently in R.  Also, there are extensions to the
     programming interface developed more recently than the reference. 
     For a discussion of details and ongoing development, see the web
     page <URL: http://developer.r-project.org/methodsPackage.html> and
     the pointers from that page.

_S_e_e _A_l_s_o:

     Classes, 'setClass', 'isClass'.

_E_x_a_m_p_l_e_s:

     getClass("numeric") ## a built in class

     cld <- getClass("thisIsAnUndefinedClass", .Force = TRUE)
     cld ## a NULL prototype
     ## If you are really curious:
     str(cld)
     ## Whereas these generate errors:
     try(getClass("thisIsAnUndefinedClass"))
     try(getClassDef("thisIsAnUndefinedClass"))

