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eieio: Predicates

 
 8 Predicates and Utilities
 **************************
 
 Now that we know how to create classes, access slots, and define
 methods, it might be useful to verify that everything is doing ok.  To
 help with this a plethora of predicates have been created.
 
  -- Function: find-class symbol &optional errorp
      Return the class that SYMBOL represents.  If there is no class,
      ‘nil’ is returned if ERRORP is ‘nil’.  If ERRORP is non-‘nil’,
      ‘wrong-argument-type’ is signaled.
 
  -- Function: class-p class
      Return ‘t’ if CLASS is a valid class vector.  CLASS is a symbol.
 
  -- Function: slot-exists-p object-or-class slot
      Non-‘nil’ if OBJECT-OR-CLASS has SLOT.
 
  -- Function: slot-boundp object slot
      Non-‘nil’ if OBJECT’s SLOT is bound.  Setting a slot’s value makes
      it bound.  Calling “slot-makeunbound” will make a slot unbound.
      OBJECT can be an instance or a class.
 
  -- Function: eieio-class-name class
      Return a string of the form ‘#<class myclassname>’ which should
      look similar to other Lisp objects like buffers and processes.
      Printing a class results only in a symbol.
 
  -- Function: class-option class option
      Return the value in CLASS of a given OPTION.  For example:
 
           (class-option eieio-default-superclass :documentation)
 
      Will fetch the documentation string for ‘eieio-default-superclass’.
 
  -- Function: eieio-object-name obj
      Return a string of the form ‘#<object-class myobjname>’ for OBJ.
      This should look like Lisp symbols from other parts of Emacs such
      as buffers and processes, and is shorter and cleaner than printing
      the object’s vector.  It is more useful to use ‘object-print’ to
      get and object’s print form, as this allows the object to add extra
      display information into the symbol.
 
  -- Function: eieio-object-class obj
      Returns the class symbol from OBJ.
 
  -- Function: eieio-object-class-name obj
      Returns the symbol of OBJ’s class.
 
  -- Function: eieio-class-parents class
      Returns the direct parents class of CLASS.  Returns ‘nil’ if it is
      a superclass.
 
  -- Function: eieio-class-parents-fast class
      Just like ‘eieio-class-parents’ except it is a macro and no type
      checking is performed.
 
  -- Function: eieio-class-parent class
      Deprecated function which returns the first parent of CLASS.
 
  -- Function: eieio-class-children class
      Return the list of classes inheriting from CLASS.
 
  -- Function: eieio-class-children-fast class
      Just like ‘eieio-class-children’, but with no checks.
 
  -- Function: same-class-p obj class
      Returns ‘t’ if OBJ’s class is the same as CLASS.
 
  -- Function: same-class-fast-p obj class
      Same as ‘same-class-p’ except this is a macro and no type checking
      is performed.
 
  -- Function: object-of-class-p obj class
      Returns ‘t’ if OBJ inherits anything from CLASS.  This is different
      from ‘same-class-p’ because it checks for inheritance.
 
  -- Function: child-of-class-p child class
      Returns ‘t’ if CHILD is a subclass of CLASS.
 
  -- Function: generic-p method-symbol
      Returns ‘t’ if ‘method-symbol’ is a generic function, as opposed to
      a regular Emacs Lisp function.
 

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