Merge pull request #56 from myarjunar/button-behavior

disable bearing distance tool when no beacons available

plugin.py

@@ -33,6 +33,7 @@
 import database
 from constants import *
 from datetime import datetime
+from utilities import validate_plugin_actions
 
 
 class RequiredLayer:
@@ -347,6 +348,7 @@ def manage_beacons(self):
                 return
         self.refresh_layers()
         BeaconManager(self.iface, self.database, self.required_layers)
+        validate_plugin_actions(self, self.database)
         self.iface.mapCanvas().refresh()
 
     def manage_parcels(self):
@@ -360,6 +362,7 @@ def manage_parcels(self):
                 return
         self.refresh_layers()
         ParcelManager(self.iface, self.database, self.required_layers)
+        validate_plugin_actions(self, self.database)
         self.iface.mapCanvas().refresh()
 
     def manage_bearing_distance(self):
@@ -372,8 +375,18 @@ def manage_bearing_distance(self):
             self.set_database_connection()
             if self.database is None:
                 return
-        self.refresh_layers()
-        BearDistManager(self.iface, self.database, self.required_layers)
+
+        result = validate_plugin_actions(self, self.database)
+        if not result:
+            QMessageBox.warning(
+                None,
+                "SML Surveyor",
+                ("No Beacons available in the table. "
+                 "Please use Beacon Manager tool to create a Beacon."))
+        else:
+            self.refresh_layers()
+            BearDistManager(self.iface, self.database, self.required_layers)
+
         self.iface.mapCanvas().refresh()
 
     def manage_database_connection(self):
@@ -384,6 +397,7 @@ def manage_database_connection(self):
         crs = database_manager.get_current_crs()
         if connection:
             self.set_database_connection(connection=connection, crs=crs)
+        validate_plugin_actions(self, self.database)
 
 
 class DatabaseManager():

utilities.py

@@ -71,6 +71,31 @@ def get_ui_class(ui_file):
     )
     return uic.loadUiType(ui_file_path, from_imports=True)[0]
 
+def validate_plugin_actions(toolbar, database):
+    """Check DB schema for actions availability. eg: Manage bearing and
+    distance action needs Beacon to be created first.
+
+    :param database: Database instance
+    :type database: database.Manager
+
+    :param toolbar: plugin toolbar
+    :type toolbar: SMLSurveyor
+
+    :return: Query result
+    :rtype: tuple
+    """
+    query = "select * from survey limit 1;"
+    try:
+        result = database.query(query=query)
+    except Exception as e:
+        raise Exception(
+            'Backend database query failed!\nError raised: %s.' % (str(e),))
+    if result:
+        toolbar.bearing_distance_action.setEnabled(True)
+    else:
+        toolbar.bearing_distance_action.setEnabled(False)
+    return result
+
 
 class ExtendedComboBox(QComboBox):
     """Extended class of QComboBox so we can perform a filtering of items.