1 ;;; eieio-base.el --- Base classes for EIEIO.
4 ;; Copyright (C) 2000, 2001, 2002, 2004, 2005, 2007 Eric M. Ludlam
6 ;; Author: <zappo@gnu.org>
7 ;; RCS: $Id: eieio-base.el,v 1.3 2007-11-26 15:01:03 michaels Exp $
10 ;; This program is free software; you can redistribute it and/or modify
11 ;; it under the terms of the GNU General Public License as published by
12 ;; the Free Software Foundation; either version 2, or (at your option)
15 ;; This program is distributed in the hope that it will be useful,
16 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
17 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18 ;; GNU General Public License for more details.
20 ;; You should have received a copy of the GNU General Public License
21 ;; along with GNU Emacs; see the file COPYING. If not, write to the
22 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
23 ;; Boston, MA 02110-1301, USA.
25 ;; Please send bug reports, etc. to zappo@gnu.org
29 ;; Base classes for EIEIO. These classes perform some basic tasks
30 ;; but are generally useless on their own. To use any of these classes,
31 ;; inherit from one or more of them.
37 ;;; eieio-instance-inheritor
39 ;; Enable instance inheritance via the `clone' method.
40 ;; Works by using the `slot-unbound' method which usually throws an
41 ;; error if a slot is unbound.
42 (defclass eieio-instance-inheritor ()
43 ((parent-instance :initarg :parent-instance
44 :type eieio-instance-inheritor-child
46 "The parent of this instance.
47 If a slot of this class is reference, and is unbound, then the parent
48 is checked for a value.")
50 "This special class can enable instance inheritance.
51 Use `clone' to make a new object that does instance inheritance from
52 a parent instance. When a slot in the child is referenced, and has
53 not been set, use values from the parent."
56 (defmethod slot-unbound ((object eieio-instance-inheritor) class slot-name fn)
57 "If a slot OBJECT in this CLASS is unbound, try to inherit, or throw a signal.
58 SLOT-NAME, is the offending slot. FN is the function signalling the error."
59 (if (slot-boundp object 'parent-instance)
60 (eieio-oref (oref object parent-instance) slot-name)
63 (defmethod clone ((obj eieio-instance-inheritor) &rest params)
64 "Clone OBJ, initializing `:parent' to OBJ.
65 All slots are unbound, except those initialized with PARAMS."
66 (let ((nobj (make-vector (length obj) eieio-unbound))
67 (nm (aref obj object-name))
68 (passname (and params (stringp (car params))))
71 (aset nobj object-class (aref obj object-class))
72 ;; The following was copied from the default clone.
75 (if (string-match "-\\([0-9]+\\)" nm)
76 (setq num (1+ (string-to-number (match-string 1 nm)))
77 nm (substring nm 0 (match-beginning 0))))
78 (aset nobj object-name (concat nm "-" (int-to-string num))))
79 (aset nobj object-name (car params)))
80 ;; Now initialize from params.
81 (if params (shared-initialize nobj (if passname (cdr params) params)))
82 (oset nobj parent-instance obj)
86 ;;; eieio-instance-tracker
88 ;; Track all created instances of this class.
89 ;; The class must initialize the `tracking-symbol' slot, and that
90 ;; symbol is then used to contain these objects.
91 (defclass eieio-instance-tracker ()
92 ((tracking-symbol :type symbol
95 "The symbol used to maintain a list of our instances.
96 The instance list is treated as a variable, with new instances added to it.")
98 "This special class enables instance tracking.
99 Inheritors from this class must overload `tracking-symbol' which is
100 a variable symbol used to store a list of all instances."
103 (defmethod initialize-instance :AFTER ((this eieio-instance-tracker)
105 "Make sure THIS is in our master list of this class.
106 Optional argument FIELDS are the initialization arguments."
107 ;; Theoretically, this is never called twice for a given instance.
108 (let ((sym (oref this tracking-symbol)))
109 (if (not (memq this (symbol-value sym)))
110 (set sym (append (symbol-value sym) (list this))))))
112 (defmethod delete-instance ((this eieio-instance-tracker))
113 "Remove THIS from the master list of this class."
114 (set (oref this tracking-symbol)
115 (delq this (symbol-value (oref this tracking-symbol)))))
117 ;; In retrospect, this is a silly function.
118 (defun eieio-instance-tracker-find (key field list-symbol)
119 "Find KEY as an element of FIELD in the objects in LIST-SYMBOL.
120 Returns the first match."
121 (object-assoc key field (symbol-value list-symbol)))
125 ;; The singleton Design Pattern specifies that there is but one object
126 ;; of a given class ever created. The EIEIO singleton base class defines
127 ;; a CLASS allocated slot which contains the instance used. All calls to
128 ;; `make-instance' will either create a new instance and store it in this
129 ;; slot, or it will just return what is there.
130 (defclass eieio-singleton ()
131 ((singleton :type eieio-singleton
134 "The only instance of this class that will be instantiated.
135 Multiple calls to `make-instance' will return this object."))
136 "This special class causes subclasses to be singletons.
137 A singleton is a class which will only ever have one instace."
140 (defmethod constructor :STATIC ((class eieio-singleton) name &rest fields)
141 "Constructor for singleton CLASS.
142 NAME and FIELDS initialize the new object.
143 This constructor guarantees that no matter how many you request,
144 only one object ever exists."
145 ;; NOTE TO SELF: In next version, make `slot-boundp' support classes
146 ;; with class allocated slots or default values.
147 (let ((old (oref-default class singleton)))
148 (if (eq old eieio-unbound)
149 (oset-default class singleton (call-next-method))
155 ;; For objects which must save themselves to disk. Provides an
156 ;; `object-write' method to save an object to disk, and a
157 ;; `eieio-persistent-read' function to call to read an object
160 ;; Also provide the method `eieio-persistent-path-relative' to
161 ;; calculate path names relative to a given instance. This will
162 ;; make the saved object location independent by converting all file
163 ;; references to be relative to the directory the object is saved to.
164 ;; You must call `eieio-peristent-path-relative' on each file name
165 ;; saved in your object.
166 (defclass eieio-persistent ()
167 ((file :initarg :file
170 "The save file for this persistent object.
171 This must be a string, and must be specified when the new object is
173 (extension :type string
177 "Extension of files saved by this object.
178 Enables auto-choosing nice file names based on name.")
179 (file-header-line :type string
181 :initform ";; EIEIO PERSISTENT OBJECT"
183 "Header line for the save file.
184 This is used with the `object-write' method."))
185 "This special class enables persistence through save files
186 Use the `object-save' method to write this object to disk. The save
187 format is Emacs Lisp code which calls the constructor for the saved
188 object. For this reason, only slots which do not have an `:initarg'
189 specified will not be saved."
192 (defmethod eieio-persistent-save-interactive ((this eieio-persistent) prompt
194 "Perpare to save THIS. Use in an `interactive' statement.
195 Query user for file name with PROMPT if THIS does not yet specify
196 a file. Optional argument NAME specifies a default file name."
197 (unless (slot-boundp this 'file)
199 (read-file-name prompt nil
201 (concat name (oref this extension))
205 (defun eieio-persistent-read (filename)
206 "Read a persistent object from FILENAME."
209 (set-buffer (get-buffer-create " *tmp eieio read*"))
212 (insert-file-contents filename nil nil nil t)
213 (goto-char (point-min))
214 (setq ret (read (current-buffer)))
215 (if (not (child-of-class-p (car ret) 'eieio-persistent))
216 (error "Corrupt object on disk"))
217 (setq ret (eval ret))
218 (oset ret file filename))
219 (kill-buffer " *tmp eieio read*"))
222 (defmethod object-write ((this eieio-persistent) &optional comment)
223 "Write persistent object THIS out to the current stream.
224 Optional argument COMMENT is a header line comment."
225 (call-next-method this (or comment (oref this file-header-line))))
227 (defmethod eieio-persistent-path-relative ((this eieio-persistent) file)
228 "For object THIS, make absolute file name FILE relative."
229 (file-relative-name (expand-file-name file)
230 (file-name-directory (oref this file))))
232 (defmethod eieio-persistent-save ((this eieio-persistent) &optional file)
233 "Save persistent object THIS to disk.
234 Optional argument FILE overrides the file name specified in the object
237 (let ((b (set-buffer (get-buffer-create " *tmp object write*")))
238 (default-directory (file-name-directory (oref this file)))
239 (cfn (oref this file)))
243 (let ((standard-output (current-buffer)))
246 (eieio-persistent-path-relative this file)
247 (file-name-nondirectory cfn)))
248 (object-write this (oref this file-header-line)))
249 (write-file cfn nil))
250 ;; Restore :file, and kill the tmp buffer
252 (setq buffer-file-name nil)
255 ;; Notes on the persistent object:
256 ;; It should also set up some hooks to help it keep itself up to date.
261 ;; Named objects use the objects `name' as a slot, and that slot
262 ;; is accessed with the `object-name' symbol.
264 (defclass eieio-named ()
267 Name storage already occurs in an object. This object provides get/set
271 (defmethod slot-missing ((obj eieio-named)
272 slot-name operation &optional new-value)
273 "Called when a on-existant slot is accessed.
274 For variable `eieio-named', provide an imaginary `object-name' slot.
275 Argument OBJ is the Named object.
276 Argument SLOT-NAME is the slot that was attempted to be accessed.
277 OPERATION is the type of access, such as `oref' or `oset'.
278 NEW-VALUE is the value that was being set into SLOT if OPERATION were
280 (if (or (eq slot-name 'object-name)
281 (eq slot-name :object-name))
282 (cond ((eq operation 'oset)
283 (if (not (stringp new-value))
284 (signal 'invalid-slot-type
285 (list obj slot-name 'string new-value)))
286 (object-set-name-string obj new-value))
287 (t (object-name-string obj)))
290 (provide 'eieio-base)
292 ;;; eieio-base.el ends here