Feature: TextField Input validation

[ndonkoHenri]

Close #631

Props:

@dataclasses.dataclass
class InputFilter:
    regex_string: str
    allow: bool = field(default=True)
    replacement_string: str = field(default="")

Example code:

import flet as ft


def main(page: ft.Page):
    page.title = "Input Filtering"
    page.add(
        ft.TextField(
            label="Only numbers are allowed :)",
            input_filter=ft.InputFilter(allow=True, regex_string=r"[0-9]"), # only allow numbers
        )
    )

ft.app(target=main)

Capture:
(when trying to add text characters they are rejected)

Notes:

• regex_string can't be passed to dart as a raw string(using the 'r')

  RegExp(regexString ?? "")

  As seen above, this is because the value of regex_string is stored in a variable (regexString).. hence using string interpolation(RegExp(r"$regexString")) for example, will cant work because the variable's name will not be interpolated (we are in raw mode).
  From RegExp docs:

Use a raw string to treat each character, including \ and $, in a string as a literal character. Each character then gets passed to the RegExp parser. You should use a raw string as the argument to the RegExp constructor.

This is my first dart contribution, hence will strongly appreciate opinions. 😄

[FeodorFitsner]

Well, looks like it's ready to merge, huh?

[ndonkoHenri]

Yh, now I think its ready!

[bobwatcherx]

i get eror for use inputfilter

Unhandled error processing page session : Traceback (most recent call last):
  File "/usr/local/lib/python3.10/dist-packages/flet_runtime/app.py", line 363, in on_session_created
    session_handler(page)
  File "/home/minx/belajar/fletval/main.py", line 9, in main
    input_filter=ft.InputFilter(allow=True, regex_string=r"[0-9]", replacement_string=""),
AttributeError: module 'flet' has no attribute 'InputFilter'

flet version

root@minx-Lenovo-V145-14AST:/home/minx/belajar/fletval# flet --version
0.12.2

code

import flet as ft


def main(page: ft.Page):
    page.title = "Input Filtering"
    page.add(
        ft.TextField(
    label="Only numbers are allowed :)",
    input_filter=ft.InputFilter(allow=True, regex_string=r"[0-9]", replacement_string=""),
) 
   )

ft.app(target=main)

[ndonkoHenri]

You need to have the latest prerelease.

pip install flet --pre

An official release is still to come.