Resolve circular imports for CuraAPI

cura/API/__init__.py

@@ -1,5 +1,7 @@
 # Copyright (c) 2018 Ultimaker B.V.
 # Cura is released under the terms of the LGPLv3 or higher.
+from typing import Optional, TYPE_CHECKING
+
 from PyQt5.QtCore import QObject, pyqtProperty
 
 from UM.PluginRegistry import PluginRegistry
@@ -7,6 +9,9 @@ from cura.API.Backups import Backups
 from cura.API.Interface import Interface
 from cura.API.Account import Account
 
+if TYPE_CHECKING:
+    from cura.CuraApplication import CuraApplication
+
 
 ##  The official Cura API that plug-ins can use to interact with Cura.
 #
@@ -19,14 +24,30 @@ class CuraAPI(QObject):
     # For now we use the same API version to be consistent.
     VERSION = PluginRegistry.APIVersion
 
-    # Backups API
-    backups = Backups()
+    def __init__(self, application: "CuraApplication") -> None:
+        super().__init__(parent = application)
+        self._application = application
 
-    # Interface API
-    interface = Interface()
+        # Accounts API
+        self._account = Account(self._application)
 
-    _account = Account()
+        # Backups API
+        self._backups = Backups(self._application)
+
+        # Interface API
+        self._interface = Interface(self._application)
+
+    def initialize(self) -> None:
+        self._account.initialize()
 
     @pyqtProperty(QObject, constant = True)
-    def account(self) -> Account:
-        return CuraAPI._account
+    def account(self) -> "Account":
+        return self._account
+
+    @property
+    def backups(self) -> "Backups":
+        return self._backups
+
+    @property
+    def interface(self) -> "Interface":
+        return self._interface