Show purchase instead of purchase line on request object

purchase_request.py

@@ -25,6 +25,9 @@ class PurchaseRequest(OSV):
         domain="[('type', '=', 'warehouse')]", readonly=True)
     purchase_line = fields.Many2One(
         'purchase.line', 'Purchase Line',readonly=True)
+    purchase = fields.Function(
+        'get_purchase', type='many2one', relation='purchase.purchase',
+        string='Purchase')
     company = fields.Many2One(
         'company.company', 'Company', required=True, readonly=True)
     state = fields.Function(
@@ -48,6 +51,15 @@ class PurchaseRequest(OSV):
                     context=context)[0]
         return False
 
+    def get_purchase(self, cursor, user, ids, name, args, context=None):
+        res = {}
+        for request in self.browse(cursor, user, ids, context=context):
+            if request.purchase_line and request.purchase_line.purchase:
+                res[request.id] = request.purchase_line.purchase.id
+            else:
+                res[request.id] = None
+        return res
+
     def get_state(self, cursor, user, ids, name, args, context=None):
         res = {}.fromkeys(ids, 'draft')
         for request in self.browse(cursor, user, ids, context=context):

purchase_request.xml

@@ -24,8 +24,8 @@
                         <field name="purchase_date"/>
                         <label name="supply_date"/>
                         <field name="supply_date"/>
-                        <label name="purchase_line"/>
-                        <field name="purchase_line"/>
+                        <label name="purchase"/>
+                        <field name="purchase"/>
                         <label name="stock_level"/>
                         <field name="stock_level"/>
                         <label name="state"/>
@@ -39,7 +39,7 @@
             <field name="type">tree</field>
             <field name="arch" type="xml">
                 <![CDATA[
-                    <tree string="Locations">
+                    <tree string="Purchase Requests">
                         <field name="product" select="1"/>
                         <field name="quantity" select="2"/>
                         <field name="uom" select="2"/>