[Question] Dynamic definition of ft.Ref not working

[Alan3344]

Question

Sample code ( I use Black Formatter / Python 3.11.4):

@dataclass
class TFStruct:

    ref: ft.Ref[ft.TextField]  # input ref
    label: str  # input label
    value: str  # input value

class FlVar:
  """Define some static variable"""

  HValues: list[str] = [...]
  
  TfRefs: list[TFStruct] = [TFStruct(ft.Ref[ft.TextField](), h, '') for h in HValues]

def addTF(label, value, ref, i):
    return ft.TextField(
        label=label,
        ref=ref,
        text_size=16,
        on_change=inputChanged,
        read_only=True if i > 7 else False,
        value=FlText.PLACEHOLDER_DEFAULT if i > 7 else value,
        max_length=FlVar.TEXT_LENGTH_1 if i < 2 else FlVar.TEXT_LENGTH_2,
        keyboard_type='number' if label != Header.Name.value else 'none',
    )

textFileds = [
    addTF(item.label, item.value, item.ref, i)
    for i, item in enumerate(FlVar.TfRefs)
]

# Finally use like this
page.add(
  ft.Container(ft.Column(textFileds))
)

for i, item in enumerate(FlVar.TfRefs):
    irc = item.ref.current
    print(irc.value)

Finally, get the value and set the value through the for loop, which is convenient for debugging. I can read and write yesterday, but now no matter how I debug, the value I get is still a null character (like '').

I don't know why, is there something wrong with my code?

Code sample

No response

Error message

No response

------------------------------------------------------

• I have searched for answers to my question both in the issues and in previous discussions.

[ndonkoHenri]

Please share some runnable code. I got alot of errors (several stuffs are undefined) when running this.

[Alan3344]

This is a simplified demo of the simplest version. After many times of debugging, it can work well as I expected.
The actual code is very long. I may have encountered some bugs and have not been able to solve it yet.
My Runtime Python 3.11.4
need pip install rich

The successful code is also posted

import inspect
import os
import re
import time
from dataclasses import dataclass
from enum import StrEnum
from random import randint
import flet as ft
from rich.console import Console


def fprint(*args, **kwargs):
    stack = inspect.stack()[1]
    line = stack.lineno
    file = stack.filename.replace(os.getcwd(), '').lstrip('/')
    info = f'[[bold red]{time.strftime("%T")}[/bold red]] {file}:{line}'
    Console().print(info, *args, **kwargs)


def getvars(obj):
    return {k: v for k, v in vars(obj).items() if not k.startswith('_')}


@dataclass
class TFStruct:
    ref: ft.Ref[ft.TextField]  # input ref
    label: str  # input label
    value: str  # input value


@dataclass
class Student:
    No: int
    Name: str
    Age: int
    ...

    def to_dict(self):
        return getvars(self)


# define table header
class Header(StrEnum):
    No = 'No'
    Name = 'Name'
    Age = 'Age'


class FlVar:
    """Define some static variable"""

    Page: ft.Page = None
    HValues: list[str] = [h.value for h in Header]
    TfRefs: list[TFStruct] = [TFStruct(ft.Ref[ft.TextField](), h, '') for h in HValues]
    InputRt: dict[str, str] = {h: '' for h in HValues}


def collectCalcData(e):
    """Handling when the input value changes"""
    data: dict = {}
    for item in FlVar.TfRefs:
        value = item.ref.current.value
        if item.label != Header.Name.value:
            if not value:
                value = 0
            else:
                value = int(value)
        data.update({Header(item.label).name: value})
    fprint('data:', data)

    # Also can use like below
    # key = None
    # if e.control.label in FlVar.HValues:
    #     key = Header(e.control.label).name
    # elif e.control.label in FlVar.HValues:
    #     key = e.control.label
    # FlVar.InputRt.update({key: e.control.value})

    # for dk, dv in FlVar.InputRt.items():
    #     if dk != 'Name':
    #         dv = int(dv) if dv else 0
    #     data.update({dk: dv})
    # Student(**data)
    # return data


def inputChanged(e):
    """Triggered when the content of the input box changes"""
    r1 = re.compile(r'^\d+$')  # Starts with a number and ends with
    r2 = re.compile(r'\D')  # Inverse match for non-digits
    m_socre = 120
    # fprint('TextFileChanged', e.control)
    e.control.value = e.control.value.strip('')

    if e.control.label != Header.Name.value:
        # Replace non-numeric with empty
        if r2.search(e.control.value):
            e.control.value = r2.sub('', e.control.value)

        # The first two digits of the match are 0
        if len(e.control.value) > 1 and e.control.value[0] == '0':
            e.control.value = e.control.value[1:]

        # Remove minus sign
        if e.control.value and e.control.value[0] == '-':
            e.control.value = e.control.value[1:]

        # Match age processing
        if e.control.label == Header.Age.value:
            if r1.match(e.control.value) and int(e.control.value) > 100:
                e.control.value = e.control.value[1:]

        # Matching score processing
        if e.control.label != Header.No.value:
            if r1.match(e.control.value) and int(e.control.value) > m_socre:
                e.control.value = e.control.value[1:]

    e.control.value = e.control.value.strip()
    collectCalcData(e)
    fprint('inputChanged', e.control.label, e.control.value)


def addTF(label, value, ref, i):
    return ft.TextField(
        label=label,
        ref=ref,
        text_size=16,
        on_change=inputChanged,
        read_only=True if i > 7 else False,
        value='0' if i > 7 else value,
        max_length=11 if i < 2 else 3,
        keyboard_type='number' if label != Header.Name.value else 'none',
    )


textFileds = [
    addTF(item.label, item.value, item.ref, i) for i, item in enumerate(FlVar.TfRefs)
]


def getValue(e=None):
    for i, item in enumerate(FlVar.TfRefs):
        irc = item.ref.current
        # fprint(irc)
    # fprint('getValue', [i for i in FlVar.TfRefs])
    fprint(
        'getValue',
        [
            (c := FlVar.TfRefs[i].ref.current, c.label, c.value)
            for i in range(len(FlVar.TfRefs))
        ],
    )


def setValue(e=None):
    ref = FlVar.TfRefs[randint(0, len(Header) - 1)].ref
    fprint('setValue(1)', ref.current)
    fprint('setValue(2)', ref.current.value)
    ref.current.value = time.ctime()
    FlVar.Page.update()  # Without this, the page's data will not be updated


# Finally use like this
def main(page: ft.Page):
    FlVar.Page = page
    page.title = 'xxx stuMgr'
    page.window_width = 800
    page.window_height = 600
    page.add(ft.Container(ft.Column(textFileds)))
    page.add(ft.ElevatedButton('getValue', on_click=getValue))
    page.add(ft.ElevatedButton('setValue', on_click=setValue))


ft.app(target=main)

[Alan3344]

I think I've found the source of the problem, I'm missing every control update FlVar.Page.update()
Now I feel like my application changes state much faster!

[ndonkoHenri]

Happy to know that your issue is now resolved.

[andrerotband]

Your code is not correct.

The parentheses are missing at the end of the statement.

Your code:

ref: ft.Ref[ft.TextField]

Correct code:

ref: ft.Ref[ft.TextField] ()

[Alan3344]

Do you mean this code, which is just a definition data structure
You can refer to dataclass usage
And it comes with the type of each member, so that you can get code hints when using it in some editors,like VS Code
ft.Ref[ft.TextField] is a typing.Generic Data Type
And ft.Ref[ft.TextField]() is an instance of a paradigm
It's like marking type str without parentheses

If you remove the type annotation after ref, you will not get code intelligence suggestions
like this code: FlVar.TfRefs[i]. ref.current
When you type . it prompts for members, which contains ref

@dataclass
class TFStruct:
    ref: ft.Ref[ft.TextField]  # input ref
    label: str  # input label
    value: str  # input value

# official procedure： /flet_core/ref.py
class Ref(Generic[T]):
    def __init__(self):
        self._current: T = None
    ...

[Alan3344]

I have been debugging this problem for a long time
gained experience:
My component is dynamically loaded and then the ref variable is also dynamically loaded, something like "Tab" 切换
When the custom control is toggled, the control is not "visible" properly, so the ref doesn't work.