Downloader

ClassSource

downloader = Downloader(
    id: str
    to_addr: Callable[[str], str] | None
)

Purely Python-Dash implemented downloader component.

This component is purely implemented by python codes.

Aliases

This class can be acquired by

import dash_file_cache as dfc


dfc.Downloader
dfc.components.Downloader
dfc.components.downloader.Downloader

Arguments

Argument	Type	Required	Description
id	str		The basic id of this component.
to_addr	Callable[[str], str] | None		An optional pre-processing function which converts the trigger from the callback to the address used for downloading the file. If not provided, will use the trigger value directly (equivalent to lambda x: x). If returning an empty string, the downloading event will be prevented.

Methods

layout

layout: html.Div = downloader.layout()

Get the layout of this component.

Returns

Argument	Type	Description
layout	html.Div	The layout of this downloader.

---

use_callbacks

downloader.use_callbacks(app: dash.Dash)

Use callbacks.

Bind the automatically generated callbacks used by this components to the given app.

Requires

Argument	Type	Required	Description
app	Dash		The dash application.

Properties

as_input

cbk_input: dash.Input = downloader.as_input

Provide the trigger as the callback input. This input should be triggered when the address of the downloadable file is prepared.

---

as_output

cbk_output: dash.Output = downloader.as_output

Provide the trigger as the callback output.

---

as_state

cbk_state: dash.State = downloader.as_state

Provide the trigger as the callback state. This input should be triggered when the address of the downloadable file is prepared.

Examples

Minimal example

Codes

minimal_example_downloader.py

from typing import Optional
import dash
import flask
from dash import html, Input
from dash_file_cache.services.utilities import get_server
from dash_file_cache.components.downloader import Downloader


app = dash.Dash("demo")
server = get_server(app)

downloader = Downloader(id="downloader", to_addr=None)

app.layout = html.Div((html.Button(id="btn", children="Download"), downloader.layout()))

downloader.use_callbacks(app)


@server.route("/file")
def file():
    resp = flask.Response("test file content", status=200, mimetype="text/plain")
    resp.headers["Content-Disposition"] = "attachment; filename=test.txt"
    return resp


@app.callback(downloader.as_output, Input("btn", "n_clicks"))
def trigger_get_file(n_clicks: Optional[int]):
    if not n_clicks:
        return dash.no_update
    return "/file"


if __name__ == "__main__":
    app.run()

Results

An application with a downloading button will be rendered.

By clicking the button, a file named text.txt will be downloaded, the file content is

test file content

Download a file with a background callback

See

Download file