Add dynamic Pydantic rules example

Author: evilkermit

README.md

@@ -6,9 +6,11 @@ This repository contains examples of how to build application functionalities in
 
 1. [Creating a form for a Pydantic model](examples/pydantic_form)
 2. [Create a JSON editor for a Pydantic model](examples/pydantic_monaco)
-3. [Working with Plotly](examples/plotly)
-4. [Working with Matplotlib](examples/matplotlib)
-5. [Synchronizing changes between tabs](examples/multitab)
+3. [Changing Pydantic rules based on user input](examples/dynamic_pydantic_rules)
+4. [Complex Pydantic rules](examples/complex_pydantic_rules)
+5. [Working with Plotly](examples/plotly)
+6. [Working with Matplotlib](examples/matplotlib)
+7. [Synchronizing changes between tabs](examples/multitab)
 
 ## Running Examples
 

examples/dynamic_pydantic_rules/main.py

@@ -0,0 +1,12 @@
+"""Runs the dynamic Pydantic rules example."""
+
+from examples.dynamic_pydantic_rules.view import App
+
+
+def main() -> None:
+    app = App()
+    app.server.start(open_browser=False)
+
+
+if __name__ == "__main__":
+    main()

examples/dynamic_pydantic_rules/model.py

@@ -0,0 +1,26 @@
+"""Model implementation for dynamic Pydantic rules example."""
+
+from pydantic import BaseModel, Field, model_validator
+from typing_extensions import Self
+
+
+class FormData(BaseModel):
+    """Pydantic model for the form data."""
+
+    min: float = Field(default=0.0, title="Minimum")
+    max: float = Field(default=10.0, title="Maximum")
+    value: float = Field(default=5.0, title="Value")
+
+    @model_validator(mode="after")
+    def validate_value_in_range(self) -> Self:
+        if self.value < self.min or self.value > self.max:
+            raise ValueError("Value must be between Minimum and Maximum")
+
+        return self
+
+
+class Model:
+    """Model implementation for dynamic Pydantic rules example."""
+
+    def __init__(self) -> None:
+        self.form = FormData()

examples/dynamic_pydantic_rules/view.py

@@ -0,0 +1,42 @@
+"""View for dynamic Pydantic rules example."""
+
+from nova.mvvm.trame_binding import TrameBinding
+from nova.trame import ThemedApp
+from nova.trame.view.components import InputField
+from nova.trame.view.layouts import GridLayout
+from trame.widgets import vuetify3 as vuetify
+
+from .model import Model
+from .view_model import ViewModel
+
+
+class App(ThemedApp):
+    """View for dynamic Pydantic rules example."""
+
+    def __init__(self) -> None:
+        super().__init__()
+
+        self.create_vm()
+        # If you forget to call connect, then the application will crash when you attempt to update the view.
+        self.view_model.form_data_bind.connect("data")
+        # Generally, we want to initialize the view state before creating the UI for ease of use. If initialization
+        # is expensive, then you can defer it. In this case, you must handle the view state potentially being
+        # uninitialized in the UI via v_if statements.
+        self.view_model.update_form_data()
+
+        self.create_ui()
+
+    def create_ui(self) -> None:
+        with super().create_ui() as layout:
+            with layout.content:
+                with vuetify.VCard(classes="mx-auto my-4", max_width=600):
+                    with GridLayout(columns=3, gap="0.5em"):
+                        InputField(v_model="data.min")
+                        InputField(v_model="data.max")
+                        InputField(v_model="data.value")
+
+    def create_vm(self) -> None:
+        binding = TrameBinding(self.state)
+
+        model = Model()
+        self.view_model = ViewModel(model, binding)

examples/dynamic_pydantic_rules/view_model.py

@@ -0,0 +1,19 @@
+"""View model implementation for dynamic Pydantic rules example."""
+
+from nova.mvvm.interface import BindingInterface
+
+from .model import Model
+
+
+class ViewModel:
+    """View model implementation for dynamic Pydantic rules example."""
+
+    def __init__(self, model: Model, binding: BindingInterface) -> None:
+        self.model = model
+
+        # self.on_update is called any time the view updates the binding.
+        self.form_data_bind = binding.new_bind(self.model.form)
+
+    def update_form_data(self) -> None:
+        # This will fail if you haven't called connect on the binding!
+        self.form_data_bind.update_in_view(self.model.form)