add tasklist example

Author: Ivan Dlugos

README.md

@@ -64,6 +64,8 @@ box.put(person)       # Update
 box.remove(person)    # Delete
 ```
 
+Additionally, see the [TaskList example app](example).
+
 For more information and code examples, see the tests folder. The docs for other languages may also help you understand the basics.
 
 * ObjectBox Java = https://docs.objectbox.io

example/.gitignore

@@ -0,0 +1 @@
+*.mdb

example/__init__.py

@@ -0,0 +1,52 @@
+from cmd import Cmd
+import objectbox
+import datetime
+from example.model import *
+
+
+# objectbox expects date timestamp in milliseconds since UNIX epoch
+def now_ms() -> int:
+    seconds: float = datetime.datetime.utcnow().timestamp()
+    return round(seconds * 1000)
+
+
+def format_date(timestamp_ms: int) -> str:
+    return "" if timestamp_ms == 0 else str(datetime.datetime.fromtimestamp(timestamp_ms / 1000))
+
+
+class TasklistCmd(Cmd):
+    prompt = "> "
+    _ob = objectbox.Builder().model(get_objectbox_model()).directory("tasklist-db").build()
+    _box = objectbox.Box(_ob, Task)
+
+    def do_ls(self, _):
+        """list tasks"""
+
+        tasks = self._box.get_all()
+
+        print("%3s  %-29s  %-29s  %s" % ("ID", "Created", "Finished", "Text"))
+        for task in tasks:
+            print("%3d  %-29s  %-29s  %s" % (
+            task.id, format_date(task.date_created), format_date(task.date_finished), task.text))
+
+    def do_new(self, text: str):
+        """create a new task with the given text (all arguments concatenated)"""
+        task = Task()
+        task.text = text
+        task.date_created = now_ms()
+        self._box.put(task)
+
+    def do_done(self, id: str):
+        """mark task with the given ID as done"""
+        task = self._box.get(int(id))
+        task.date_finished = now_ms()
+        self._box.put(task)
+
+    def do_exit(self, _):
+        """close the program"""
+        raise SystemExit()
+
+
+if __name__ == '__main__':
+    app = TasklistCmd()
+    app.cmdloop('Welcome to the ObjectBox tasks-list app example. Type help or ? for a list of commands.')

example/__main__.py

@@ -0,0 +1,18 @@
+from objectbox.model import *
+
+
+@Entity(id=1, uid=1)
+class Task:
+    id = Id(id=1, uid=1001)
+    text = Property(str, id=2, uid=1002)
+
+    # TODO property type DATE
+    date_created = Property(int, id=3, uid=1003)
+    date_finished = Property(int, id=4, uid=1004)
+
+
+def get_objectbox_model():
+    m = Model()
+    m.entity(Task, last_property_id=IdUid(4, 1004))
+    m.last_entity_id = IdUid(1, 1)
+    return m