[Matlab] Consistently use nix.Utils.fetchObj

Use of nix.Utils.fetchObj was added to
- MultiTag.open_positions
- MultiTag.open_extents
- Section.parent
- Section.openLink

Author: mpsonntag

+nix/MultiTag.m

@@ -151,11 +151,7 @@
 
         function r = open_positions(obj)
             fname = strcat(obj.alias, '::openPositions');
-            h = nix_mx(fname, obj.nix_handle);
-            r = {};
-            if h ~= 0
-                r = nix.DataArray(h);
-            end
+            r = nix.Utils.fetchObj(fname, obj.nix_handle, @nix.DataArray);
         end
 
         function [] = add_positions(obj, add_this)
@@ -175,11 +171,7 @@
 
         function r = open_extents(obj)
             fname = strcat(obj.alias, '::openExtents');
-            h = nix_mx(fname, obj.nix_handle);
-            r = {};
-            if h ~= 0
-                r = nix.DataArray(h);
-            end
+            r = nix.Utils.fetchObj(fname, obj.nix_handle, @nix.DataArray);
         end
 
         function [] = set_extents(obj, add_this)

+nix/Section.m

@@ -30,11 +30,7 @@
 
         function r = parent(obj)
             fname = strcat(obj.alias, '::parent');
-            h = nix_mx(fname, obj.nix_handle);
-            r = {};
-            if h ~= 0
-                r = nix.Section(h);
-            end
+            r = nix.Utils.fetchObj(fname, obj.nix_handle, @nix.Section);
         end
 
         % ----------------
@@ -59,11 +55,7 @@
 
         function r = openLink(obj)
             fname = strcat(obj.alias, '::openLink');
-            h = nix_mx(fname, obj.nix_handle);
-            r = {};
-            if h ~= 0
-                r = nix.Section(h);
-            end
+            r = nix.Utils.fetchObj(fname, obj.nix_handle, @nix.Section);
         end
 
         function r = inherited_properties(obj)

+nix/Utils.m

@@ -31,12 +31,11 @@
             end
         end
 
-        function rcell = fetchObj(nixMxFunc, handle, objConstructor)
+        function r = fetchObj(nixMxFunc, handle, objConstructor)
+            r = {};
             h = nix_mx(nixMxFunc, handle);
             if (h ~= 0)
-                rcell = objConstructor(h);
-            else
-                rcell = {};
+                r = objConstructor(h);
             end
         end