Improve converters.

Replace old syntax with new one and improve
implementation.

test/autotest/test_suite/json_book_collection_converter.e

@@ -4,7 +4,8 @@ note
     date: "$Date$"
     revision: "$Revision$"
 
-class JSON_BOOK_COLLECTION_CONVERTER
+class
+	JSON_BOOK_COLLECTION_CONVERTER
 
 inherit
     JSON_CONVERTER
@@ -30,30 +31,32 @@ feature -- Conversion
 
     from_json (j: like to_json): detachable like object
         local
-            ucs: detachable STRING_32
-            ll: LINKED_LIST [BOOK]
-            b: detachable BOOK
-            ja: detachable JSON_ARRAY
-            i: INTEGER
+            l_books: LINKED_LIST [BOOK]
         do
-            ucs ?= json.object (j.item (name_key), Void)
-            check ucs /= Void end
-            create Result.make (ucs)
-            ja ?= j.item (books_key)
-            check ja /= Void end
-            from
-                i := 1
-                create ll.make
-            until
-                i > ja.count
-            loop
-                b ?= json.object (ja [i], "BOOK")
-                check b /= Void end
-                ll.force (b)
-                i := i + 1
+            if
+				attached {STRING_32} json.object (j.item (name_key), Void) as l_name and
+				attached {JSON_ARRAY} j.item (books_key) as l_json_array
+            then
+				create Result.make (l_name)
+				create l_books.make
+
+				across
+					l_json_array as it
+				until
+					Result = Void
+				loop
+					if attached {BOOK} json.object (it.item, "BOOK") as l_book then
+						l_books.extend (l_book)
+					else
+						Result := Void
+							-- Failed
+					end
+				end
+
+				if Result /= Void then
+					Result.add_books (l_books)
+				end
             end
-            check ll /= Void end
-            Result.add_books (ll)
         end
 
     to_json (o: like object): JSON_OBJECT
@@ -66,11 +69,13 @@ feature -- Conversion
 feature    {NONE} -- Implementation
 
     name_key: JSON_STRING
+			-- Collection's name label.
         once
             create Result.make_json ("name")
         end
 
     books_key: JSON_STRING
+			-- Book list label.
         once
             create Result.make_json ("books")
         end