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Changes between Initial Version and Version 1 of CookBookTreeStructure


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Timestamp:
04/02/06 11:27:42 (8 years ago)
Author:
boxed@…
Comment:

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  • CookBookTreeStructure

    v1 v1  
     1First of all there needs to be support for a pre-commit handler if you're using the 0.9x versions of django. The patch for this is: 
     2{{{ 
     3Index: django/core/meta/__init__.py 
     4=================================================================== 
     5--- django/core/meta/__init__.py        (revision 2013) 
     6+++ django/core/meta/__init__.py        (working copy) 
     7@@ -1026,6 +1026,11 @@ 
     8             ','.join(placeholders)), db_values) 
     9         if opts.has_auto_field and not pk_set: 
     10             setattr(self, opts.pk.attname, db.get_last_insert_id(cursor, opts.db_table, opts.pk.column)) 
     11+ 
     12+    # Run any pre-commit hooks. 
     13+    if hasattr(self, '_pre_commit'): 
     14+        self._pre_commit(opts, cursor) 
     15+     
     16     db.db.commit() 
     17     # Run any post-save hooks. 
     18     if hasattr(self, '_post_save'): 
     19@@ -1696,6 +1701,7 @@ 
     20     man.save = curry(manipulator_save, opts, klass, add, change) 
     21     man.get_related_objects = curry(manipulator_get_related_objects, opts, klass, add, change) 
     22     man.flatten_data = curry(manipulator_flatten_data, opts, klass, add, change) 
     23+    man.Klass = klass 
     24     for field_name_list in opts.unique_together: 
     25         setattr(man, 'isUnique%s' % '_'.join(field_name_list), curry(manipulator_validator_unique_together, field_name_list, opts)) 
     26     for f in opts.fields: 
     27}}} 
     28 
     29Create helper methods for iterating through the parents (like in [wiki:CookBookCategoryDataModel A "category" data model] but I made it more general to avoid code duplication): 
     30{{{ 
     31def foo_recurse_list(obj, parent_field, value_field): 
     32    parent_list = [] 
     33    try: 
     34        if getattr(obj, 'parent_'+parent_field+'_id'): 
     35            p = getattr(obj, 'get_parent_'+parent_field)() 
     36            if value_field: 
     37                f = getattr(p, value_field) 
     38                parent_list.append(f) 
     39            else: 
     40                parent_list.append(p) 
     41            more = recurse_list(p, parent_field, value_field) 
     42            parent_list.extend(more) 
     43    finally: 
     44        return parent_list 
     45 
     46def recurse_list(obj, parent_field, value_field): 
     47    parent_list = foo_recurse_list(obj, parent_field, value_field) 
     48    parent_list.reverse() 
     49    return parent_list 
     50}}} 
     51 
     52In your model you will have a foreign key pointing to the parent element of each element and a character field that will be used to store the structure (called "cache_hierarchy" in my code). Then add a _pre_commit handler like this: 
     53{{{ 
     54    def _pre_commit(self, opts, cursor): 
     55        # TODO: import above and remove this import line when django gets the no-magic patches 
     56        from where_ever_you_put_the_code_above import recurse_list 
     57        parent_list = recurse_list(self, 'your_model_name_here', 'id') 
     58        if self.id in parent_list: 
     59            raise 'Cannot be a child of itself' 
     60         
     61        parent_list.append(self.id) 
     62 
     63        self.cache_hierarchy = '/'.join([str(i) for i in parent_list]) 
     64         
     65        cursor.execute("UPDATE %s SET cache_hierarchy = %%s WHERE id=%%s" % (db.quote_name(opts.db_table)), [self.cache_hierarchy, self.id]) 
     66}}}