33_update_user_func.md

Create Update User Function

- Understand a problem caused by cached user data.
- Write a function to update user details and refresh the cache.
- Modify the SetDetailsComponent to use the new function.
- Test the functionality to ensure updates are reflected immediately.

Another problem that was identified through testing, is an issue with the SetDetailsComponent. When a user changes their details, and saves, the AccountComponent continues to display their old details.

Planning

This problem also stems from the system continuing to use the cached user data. The button_save_click hander in the SetDetailsComponent writes the new data to the database, but the cached user data doesn't change. When the AccountComponent loads it uses the cached (i.e. old) user data.

To resolve this we will need reload the cached user data after the new data is sent to the database.

Code

Again, we will need to make a new function in the data_access module which will:

• write new data to the database
• reload the cached user data

1. Open the data_access module
2. Add the following code to the bottom of the module

:linenos:
:lineno-start: 26
:emphasize-lines: 1-7
def update_user(first_name, last_name):
  global __user
  
  print("Writing user details to database")
  anvil.server.call('update_user', first_name, last_name)
  __user = None
  __user = the_user()

:class: notice
- **line 26** → creates the **update_user** function which requires **first_name** and **last_name** to be passed.
- **line 27** → allows the function to edit the value of `__user`
- **line 29** → informs the developer that the database is being accessed
- **line 30** → writes the new user data to the database
- **line 31** → clears the cached user data
- **line 32** → caches the new user data

Then we need to change the code of the button_save_click hander in the SetDetailsComponent

3. Open SetDetailsComponent
4. Replace lines 36 - 38 with the highlighted code below

:linenos:
:lineno-start: 23
:emphasize-lines: 14 - 15
  def button_save_click(self, **event_args):
    
    if self.text_box_first_name.text == "":
      self.label_error.text = "First name cannot be blank"
      self.label_error.visible = True
      return

    if self.text_box_last_name.text == "":
      self.label_error.text = "Last name cannot be blank"
      self.label_error.visible = True
      return

    self.label_error.visible = False
    data_access.update_user(self.text_box_first_name.text, 
                            self.text_box_last_name.text)

    main_form = get_open_form()
    main_form.switch_component("account")

:class: notice
- **lines 36 - 37** → calls the **update_user** function pass in the values from the first_name and last_name text boxes.

Testing

Launch your web app and change the details of a user. When you click on the save button, the account page should show the new details.

Final code state

By the end of this tutorial your code should be the same as below:

Final data_access

:linenos:
import anvil.server
import anvil.users
import anvil.tables as tables
import anvil.tables.query as q
from anvil.tables import app_tables

# cached values
__user = None

def the_user():
  global __user

  if __user:
    print("Using cached user")
    return __user

  print("Accessing user from database")
  __user = anvil.users.get_user()
  return __user

def logout():
  global __user
  __user = None
  anvil.users.logout()

def update_user(first_name, last_name):
  global __user
  
  print("Writing user details to database")
  anvil.server.call('update_user', first_name, last_name)
  __user = None
  __user = the_user()

Final SetDetailsComponent

:linenos:
from ._anvil_designer import SetDetailsComponentTemplate
from anvil import *
import anvil.server
import anvil.tables as tables
import anvil.tables.query as q
from anvil.tables import app_tables
import anvil.users
from .. import data_access


class SetDetailsComponent(SetDetailsComponentTemplate):
  def __init__(self, **properties):
    # Set Form properties and Data Bindings.
    self.init_components(**properties)

    # Any code you write here will run before the form opens.
    user = data_access.the_user()
    if user["first_name"]:
      self.text_box_first_name.text = user["first_name"]
    if user["last_name"]:
      self.text_box_last_name.text = user["last_name"]

  def button_save_click(self, **event_args):
    
    if self.text_box_first_name.text == "":
      self.label_error.text = "First name cannot be blank"
      self.label_error.visible = True
      return

    if self.text_box_last_name.text == "":
      self.label_error.text = "Last name cannot be blank"
      self.label_error.visible = True
      return

    self.label_error.visible = False
    data_access.update_user(self.text_box_first_name.text, 
                            self.text_box_last_name.text)

    main_form = get_open_form()
    main_form.switch_component("account")