utils: add Unique wtforms validator

The Unique validator could check, if the value of the form field does
not alreadyy exists in the database for a specific field of a peewee model.

1 files changed, 17 insertions, 0 deletions

diff --git a/utils.py b/utils.py
index 147f048..f414d1b 100644
--- a/utils.py
+++ b/utils.py
@@ -1,5 +1,6 @@
 from functools import wraps
 from flask import request, render_template
+from wtforms import ValidationError
 
 # using http://flask.pocoo.org/docs/patterns/viewdecorators/
 def templated(template=None):
@@ -18,3 +19,19 @@ def templated(template=None):
             return render_template(template_name, **ctx)
         return decorated_function
     return decorator
+
+class Unique(object):
+    """ validator that checks field uniqueness """
+    def __init__(self, model, field, message=None):
+        self.model = model
+        self.field = field
+        if not message:
+            message = u'This element already exists.'
+        self.message = message
+
+    def __call__(self, form, field):         
+        try:
+            self.model.get(self.field == field.data)
+            raise ValidationError(self.message)
+        except self.model.DoesNotExist:
+            pass