[elpa] externals/ebdb 423be4d 14/33: Add ebdb-field-singleton abstract field class

[Eric Abrahamsen]

branch: externals/ebdb
commit 423be4dcdbbae6d75c8c8aca3e5aa993c523b698
Author: Eric Abrahamsen <address@hidden>
Commit: Eric Abrahamsen <address@hidden>

    Add ebdb-field-singleton abstract field class
    
    * ebdb.el (ebdb-field-singleton): Records can only hold one instance
      of any field subclassing this class.
      (ebdb-record-insert-field): Check for existing same-class instance,
      and delete it if present.
---
 ebdb.el | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/ebdb.el b/ebdb.el
index cab67e2..535f4ef 100644
--- a/ebdb.el
+++ b/ebdb.el
@@ -1124,6 +1124,18 @@ process."
   displayed in the *EBDB* buffer.  Use for mildly sensitive
   information.")
 
+;;; The singleton field type.  Records may only have one instance of
+;;; fields of this type.  (Unrelated to `eieio-singleton'.)
+
+;; There's a method of `ebdb-record-insert-field' for this class down
+;; under the definition of `ebdb-record'.
+(defclass ebdb-field-singleton (ebdb-field)
+  nil
+  :abstract t
+  :documentation
+  "A field class mixin that ensures a record can only have one
+  instance of that field class.")
+
 ;;; User-defined fields.  There are two kinds.  The first is
 ;;; `ebdb-field-user', which provides no information about labels or
 ;;; slots, but simply gives us the right to live in the "fields" slot
@@ -2629,6 +2641,17 @@ by the field, or else raising the error 
`ebdb-related-unfound'.")
 ;; The following functions are here because they need to come after
 ;; `ebdb-record' has been defined.
 
+(cl-defmethod ebdb-record-insert-field ((record ebdb-record)
+                                       (field ebdb-field-singleton)
+                                       &optional slot)
+  (let ((existing (ebdb-record-field record (eieio-object-class field))))
+    (when existing
+      (ebdb-record-delete-field record existing))
+    (condition-case nil
+       (cl-call-next-method)
+      ;; Put the old one back if something goes wrong.
+      (error (ebdb-record-insert-field record existing)))))
+
 (cl-defmethod ebdb-field-image-get ((field ebdb-field-image) (record 
ebdb-record))
   "Return the image for image field FIELD.