Objectified all the functional stuff in backend.__init__.

Moved all the function in backend.__init__ into the SystemWrapper class.
And also make loading the real system lazy. Reason: So I do not need to
care about whether anything imports the system before the MainWindow is
started.

2 files changed, 34 insertions, 32 deletions

diff --git a/portato/backend/__init__.py b/portato/backend/__init__.py
index 8eae806..4f20a18 100644
--- a/portato/backend/__init__.py
+++ b/portato/backend/__init__.py
@@ -16,9 +16,6 @@ from ..helper import debug
 from .system_interface import SystemInterface
 from .exceptions import BlockedException, PackageNotFoundException, DependencyCalcError, InvalidSystemError
 
-SYSTEM = "portage" # the name of the current system
-_sys = None # the SystemInterface-instance
-
 class _Package (object):
     """Wrapping class from which L{portato.backend.Package} inherits. This is used by the flags module to check
     whether an object is a package. It cannot use the normal Package class as this results in cyclic dependencies."""
@@ -26,42 +23,48 @@ class _Package (object):
     def __init__ (self):
         raise TypeError, "Calling __init__ on portato.backend._Package objects is not allowed."
 
+def is_package(what):
+    return isinstance(what, _Package)
+
 class SystemWrapper (SystemInterface):
     """This is a wrapper to the different system interfaces, allowing the direct import via C{from portato.backend import system}.
     With this wrapper a change of the system is propagated to all imports."""
     
+    __system = 'portage'
+    __wrapped_sys = None
+    __slots__ = ('__system', '__wrapped_sys', 'set_system', '__load')
+
     def __getattribute__ (self, name):
         """Just pass all attribute accesses directly to _sys."""
-        return getattr(_sys, name)
 
-def set_system (new_sys):
-    """Sets the current system to a new one.
+        if name in SystemWrapper.__slots__:
+            return object.__getattribute__(self, name)
+        
+        if SystemWrapper.__wrapped_sys is None:
+            SystemWrapper.__load()
 
-    @param new_sys: the name of the system to take
-    @type new_sys: string"""
+        return getattr(SystemWrapper.__wrapped_sys, name)
 
-    global SYSTEM
-    if new_sys != SYSTEM:
-        SYSTEM = new_sys
-        load_system()
+    @classmethod
+    def set_system (cls, system):
+        """Sets the current system to a new one.
 
-def load_system ():
-    """Loads the current chosen system.
+        @param system: the name of the system to take
+        @type system: string"""
 
-    @raises InvalidSystemError: if an inappropriate system is set"""
-    
-    global _sys
+        cls.__system = system
+        cls.__wrapped_sys = None
 
-    if SYSTEM == "portage":
-        debug("Setting Portage System")
-        from .portage import PortageSystem
-        _sys = PortageSystem ()
-    else:
-        raise InvalidSystemError, SYSTEM
+    @classmethod
+    def __load (cls):
+        """Loads the current chosen system.
 
-system = SystemWrapper()
+        @raises InvalidSystemError: if an inappropriate system is set"""
+        if cls.__system == "portage":
+            debug("Setting Portage System")
+            from .portage import PortageSystem
+            cls.__wrapped_sys = PortageSystem ()
+        else:
+            raise InvalidSystemError, cls.__system
 
-def is_package(what):
-    return isinstance(what, _Package)
-
-load_system()
+system = SystemWrapper()
diff --git a/portato/gui/utils.py b/portato/gui/utils.py
index 8b88b23..47f6fb7 100644
--- a/portato/gui/utils.py
+++ b/portato/gui/utils.py
@@ -21,7 +21,7 @@ from threading import Thread
 import gtk
 
 # some backend things
-from ..backend import flags, set_system
+from ..backend import flags, system
 from ..helper import debug, info
 from ..log import set_log_level
 from ..constants import APP, LOCALE_DIR
@@ -90,9 +90,8 @@ class Config (ConfigParser):
         set_log_level(level)
 
     def modify_system_config (self):
-        """Sets the system config.
-        @see: L{backend.set_system()}"""
-        set_system(self.get("system"))
+        """Sets the system config."""
+        system.set_system(self.get("system"))
 
     def modify_external_configs (self):
         """Convenience function setting all external configs."""