Downloader

ClassComponentSource

comp = Downloader(
    id: str | Mapping[str, Any],
    url: str | DownloaderURL,
    headers: Mapping[str, str],
    allow_cross_origin: bool,
    status: DownloaderStatus,
    mitm: str | None,
    loading_state: LoadingState
)

Downloader is a React component based on StreamSaver.

The StreamSaver.js project provides a customizable way to access and download an online stream. This is the recommended downloader for practical uses. It has the optimized performance for triggering multiple downloading events.

Aliases

This type can be acquired by

import dash_file_cache as dfc


dfc.Downloader
dfc.components.Downloader

Component Properties

Descriptions

Name	Type	Description
id	str | Mapping[str, Any]	The ID of the component. A dictionary-id is used for creating a pattern-matching callback.
url	str | DownloaderURL	The URL used to access the data to be downloaded. Each time when this value is set, a download event will be triggered. After triggering the download event, this value will be reset by a blank string.
headers	Mapping[str, str]	The extra headers to be used when submitting the request of the downloading event. This property may need to be configured when the downloading event needs to add authentication information.
allow_cross_origin	bool	A flag determining whether the cross-origin downloading link can be used. If the data to be downloaded is from a cross-domain site, need to configure this value as True while the remote site needs to configure the headers Access-Control-Allow-Origin.
status	DownloaderStatus	The status code when a downloading event is finalized. If multiple downloading events are triggered by the same downloader, the later event will overwrite the status from the former events.
mitm	str | None	The MITM-IFrame used for maintaining the status of the downloader. It prevents the downloader to be closed when the broswer is idle. See details here. If not specified, will use the default MITM service of StreamSaver.js, which needs the Internet.
loading_state	LoadingState	The loading state set by Dash. This value should not be used by users.

Properties

Name	Type	Interactive	Setable	Required	Default
id	str | Mapping[str, Any]				undefined
url	str | DownloaderURL				""
headers	Mapping[str, str]				undefined
allow_cross_origin	bool				False
status	DownloaderStatus				undefined
mitm	str | None				undefined
loading_state	LoadingState				undefined

• "Interactive" means that the property can be changed by users' interactions, thus firing a callback.
• "Setable" means that changing it by callback Output(...) will take effects.
• "Required" means that the component cannot be initialized if this value is not explicitly provided.

Examples

Minimal example

Codes

minimal_example_downloader.py

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


app = dash.Dash("demo")
ServiceDownloader("/dfc-downloader").serve(app)
server = get_server(app)

app.layout = html.Div(
    (
        html.Button(id="btn", children="Download"),
        Downloader(id="downloader", mitm="/dfc-downloader"),
    )
)


@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(Output("downloader", "url"), 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