Utils

Client and server-side utility functions.

import_module

Very similar to python’s importlib.import_module implementation. Use in the same way.

Takes two arguments, the name to import, and an optional package.

The ‘package’ argument is required when performing a relative import. It specifies the package to use as the anchor point from which to resolve the relative import to an absolute import.

Example implementation:

from anvil_extras.utils import import_module
from functools import cache

class MainForm(MainFormTemplate):
    ...

    def link_click(self, sender, **event_args):
        self.load_form(sender.tag)

    @cache
    def get_form(self, form_name):
        form_module = import_module(f".{form_name}", __package__)
        form_cls = getattr(form_module, form_name)
        return form_cls()


    def load_form(self, form_name):
        form = self.get_form(form_name)
        self.content_panel.clear()
        self.content_panel.add_component(form)

Timing

timed decorator

Import the timed decorator and apply it to a function:

import anvil.server
from anvil_extras.utils import timed


@anvil.server.callable
@timed
def target_function(args, **kwargs):
    print("hello world")

The decorator takes a logging.Logger instance as one of its optional keyword arguments. On both the server and the client this can be a Logger from the anvil_extras logging module. On the server, this can be from the Python logging module.

The decorator also takes an optional level keyword argument which must be one of the standard levels from the logging module. When no argument is passed, the default level is logging.INFO.

The default logger is an anvil_extras Logger instance, which will log to stdout. Messages will appear in your App’s logs and the IDE console. You can, however, create your own logger and pass that instead if you need more sophisticated behaviour:

import logging
from anvil_extras.utils import timed

my_logger = logging.getLogger(__name__)


@timed(logger=my_logger, level=logging.DEBUG)
def target_function(args, **kwargs):
    ...

from anvil_extras.utils import timed, logging

my_logger = logging.Logger(name="Timing", format={"{name}: {time:%H:%M:%S}-{msg}"}, level=logging.DEBUG)

@timed(logger=my_logger, level=logging.DEBUG)
def target_function(args, **kwargs):
    ...

Auto-Refresh

Whenever you set a form’s item attribute, the form’s refresh_data_bindings method is called automatically.

The utils module includes a decorator you can add to a form’s class so that refresh_data_bindings is called whenever item changes at all.

To use it, import the decorator and apply it to the class for a form:

from anvil_extras.utils import auto_refreshing
from ._anvil_designer import MyFormTemplate


@auto_refreshing
class MyForm(MyFormTemplate):
    def __init__(self, **properties):
        self.init_components(**properties)

The form’s item property will be proxied.

If your original item was a dictionary, whenever a value of the proxied item changes, the form’s refresh_data_bindings method will be called.

Note that the proxied item will make changes to the original item.

It shouldn’t matter what the original item is. It could be a dictionary, app_table Row or some other obsucre object.

Wait for writeback

Using wait_for_writeback as a decorator prevents a function from executing before any queued writebacks have been completed.

This is particularly useful if you have a form with text fields. Race conditions can occur between a text field writing back to an item and a click event that uses the item.

To use wait_for_writeback, import the decorator and apply it to a function, usually an event_handler:

from anvil_extras.utils import wait_for_writeback

class MyForm(MyFormTemplate):
     ...

     @wait_for_writeback
     def button_1_click(self, **event_args):
         anvil.server.call("save_item", self.item)

The click event will now only be called after all active writebacks have finished executing.

Correct Canvas Resolution

Canvas elements can appear blurry on retina screens. This helper function ensures a canvas element appears sharp. It should be called inside the canvas reset event.

from anvil_extras.utils import correct_canvas_resolution

class MyForm(MyFormTemplate):
     ...

     def canvas_reset(self, **event_args):
         c = self.canvas
         correct_canvas_resolution(c)
         ...