add schedule_render() method to AbstractComponent

Author: rmorshea

idom/__init__.py

@@ -11,7 +11,7 @@
 
 from .utils import Ref, html_to_vdom
 
-from .core.component import component, Component
+from .core.component import component, Component, AbstractComponent
 from .core.events import event, Events
 from .core.layout import Layout
 from .core.vdom import vdom, VdomDict
@@ -64,4 +64,5 @@
     "widgets",
     "client",
     "install",
+    "AbstractComponent",
 ]

idom/core/component.py

@@ -2,7 +2,9 @@
 import inspect
 from functools import wraps
 from typing import TYPE_CHECKING, Dict, Callable, Any, Tuple, Union
+from weakref import ReferenceType
 
+from .hooks import LifeCycleHook
 
 if TYPE_CHECKING:  # pragma: no cover
     from .vdom import VdomDict  # noqa
@@ -28,16 +30,41 @@ def constructor(*args: Any, **kwargs: Any) -> Component:
 
 
 class AbstractComponent(abc.ABC):
+    """A base class for all component implementations"""
 
-    __slots__ = [] if hasattr(abc.ABC, "__weakref__") else ["__weakref__"]
+    __slots__ = ["_life_cycle_hook"]
+    if not hasattr(abc.ABC, "__weakref__"):
+        __slots__.append("__weakref__")
+
+    # When a LifeCyleHook is created it will bind a WeakReference of itself to the its
+    # component. This is only useful for class-based component implementations. For
+    # functional components, the LifeCycleHook is accessed by getting the current_hook().
+    _life_cycle_hook: "ReferenceType[LifeCycleHook]"
 
     @abc.abstractmethod
     def render(self) -> "VdomDict":
         """Render the component's :ref:`VDOM <VDOM Mimetype>` model."""
 
+    def schedule_render(self):
+        """Schedule a re-render of this component
+
+        This is only used by class-based component implementations. Most components
+        should be functional components that use hooks to schedule renders and save
+        state.
+        """
+        try:
+            hook = self._life_cycle_hook()
+        except AttributeError:
+            raise RuntimeError(
+                f"Component {self} has no hook. Are you rendering in a layout?"
+            )
+        else:
+            assert hook is not None, f"LifeCycleHook for {self} no longer exists"
+            hook.schedule_render()
+
 
 class Component(AbstractComponent):
-    """An object for rending component models."""
+    """A functional component"""
 
     __slots__ = (
         "_function",

idom/core/hooks.py

@@ -13,16 +13,20 @@
     Union,
     NamedTuple,
     List,
+    TYPE_CHECKING,
     overload,
     cast,
 )
+from weakref import ref
+
 from typing_extensions import Protocol
 
 from loguru import logger
 
 from idom.utils import Ref
 
-from .component import AbstractComponent
+if TYPE_CHECKING:  # pragma: no cover
+    from .component import AbstractComponent
 
 
 __all__ = [
@@ -382,10 +386,11 @@ class LifeCycleHook:
 
     def __init__(
         self,
-        component: AbstractComponent,
-        schedule_render: Callable[[AbstractComponent], None],
+        component: "AbstractComponent",
+        schedule_render: Callable[["AbstractComponent"], None],
     ) -> None:
         self.component = component
+        component._life_cycle_hook = ref(self)
         self._schedule_render_callback = schedule_render
         self._schedule_render_later = False
         self._is_rendering = False

tests/test_core/test_element.py renamed to tests/test_core/test_component.py

@@ -1,3 +1,5 @@
+import pytest
+
 import idom
 
 
@@ -68,3 +70,40 @@ def PreFormated():
         pre.get_attribute("innerHTML")
         == "<span>this<span>is</span>some</span>pre-formated text"
     )
+
+
+def test_class_component(driver, display, driver_wait):
+    class Counter(idom.AbstractComponent):
+        def __init__(self):
+            self.count = 0
+
+        def render(self):
+            return idom.html.button(
+                {"onClick": lambda event: self._increment_count(), "id": "counter"},
+                f"Clicked {self.count} times",
+            )
+
+        def _increment_count(self):
+            self.count += 1
+            self.schedule_render()
+
+    display(Counter)
+
+    client_counter = driver.find_element_by_id("counter")
+
+    for i in range(5):
+        driver_wait.until(
+            lambda d: client_counter.get_attribute("innerHTML") == f"Clicked {i} times"
+        )
+        client_counter.click()
+
+
+def test_class_component_has_no_hook():
+    class MyComponent(idom.AbstractComponent):
+        def render(self):
+            ...
+
+    component = MyComponent()
+
+    with pytest.raises(RuntimeError, match="no hook"):
+        component.schedule_render()