Add FieldList wrapper for grid columns list

needs to be merged with the "forms2" equivalent at some point...

tailbone/grids/core.py

@@ -48,6 +48,20 @@ from tailbone.db import Session
 from tailbone.util import raw_datetime
 
 
+class FieldList(list):
+    """
+    Convenience wrapper for a field list.
+    """
+
+    def insert_before(self, field, newfield):
+        i = self.index(field)
+        self.insert(i, newfield)
+
+    def insert_after(self, field, newfield):
+        i = self.index(field)
+        self.insert(i + 1, newfield)
+
+
 class Grid(object):
     """
     Core grid class.  In sore need of documentation.
@@ -63,7 +77,7 @@ class Grid(object):
 
         self.key = key
         self.data = data
-        self.columns = columns
+        self.columns = FieldList(columns) if columns is not None else None
         self.width = width
         self.request = request
         self.mobile = mobile
@@ -114,6 +128,12 @@ class Grid(object):
         if key in self.columns:
             self.columns.remove(key)
 
+    def insert_before(self, field, newfield):
+        self.columns.insert_before(field, newfield)
+
+    def insert_after(self, field, newfield):
+        self.columns.insert_after(field, newfield)
+
     def set_joiner(self, key, joiner):
         if joiner is None:
             self.joiners.pop(key, None)