examples: add examples/vweb/server_sent_events; implement vweb.sse
Delyan Angelov
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body {
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font-family: Arial, Helvetica, sans-serif;
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color: #eee;
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background-color: #333;
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background-image: url("v-logo.svg");
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background-repeat: no-repeat;
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background-size: 10em;
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margin: 0;
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padding-left: 11em;
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}
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h1 {
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color: #6699CC;
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}
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img.logo {
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float: left;
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width: 10em;
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}
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@ -0,0 +1 @@
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<?xml version="1.0" encoding="UTF-8" standalone="no"?><!-- Generator: Gravit.io --><svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" style="isolation:isolate" viewBox="0 0 500 500" width="500px" height="500px"><defs><clipPath id="_clipPath_8TWIgR1z3pxinjWBiigzcEIrVJKv9Gq4"><rect width="500" height="500"/></clipPath></defs><g clip-path="url(#_clipPath_8TWIgR1z3pxinjWBiigzcEIrVJKv9Gq4)"><path d=" M 318.422 453.543 L 463.705 49.541 C 466.168 42.689 462.285 37.693 455.037 38.392 L 340.786 49.398 C 333.539 50.097 325.71 56.246 323.316 63.121 L 188.843 449.216 C 186.447 456.091 190.414 461.673 197.695 461.673 L 308.901 461.673 C 312.541 461.673 316.497 458.893 317.729 455.466 L 318.422 453.543 Z " fill="rgb(83,107,138)"/><defs><filter id="Hmac7mZraFWHw0G84Yxj4QuzeTFp0E7Y" x="-200%" y="-200%" width="400%" height="400%" filterUnits="objectBoundingBox" color-interpolation-filters="sRGB"><feGaussianBlur xmlns="http://www.w3.org/2000/svg" in="SourceGraphic" stdDeviation="6.440413594258542"/><feOffset xmlns="http://www.w3.org/2000/svg" dx="0" dy="0" result="pf_100_offsetBlur"/><feFlood xmlns="http://www.w3.org/2000/svg" flood-color="#000000" flood-opacity="0.65"/><feComposite xmlns="http://www.w3.org/2000/svg" in2="pf_100_offsetBlur" operator="in" result="pf_100_dropShadow"/><feBlend xmlns="http://www.w3.org/2000/svg" in="SourceGraphic" in2="pf_100_dropShadow" mode="normal"/></filter></defs><g filter="url(#Hmac7mZraFWHw0G84Yxj4QuzeTFp0E7Y)"><path d=" M 301.848 455.466 L 241.359 280.725 L 250 275.324 L 311.57 453.543 L 301.848 455.466 Z " fill="rgb(235,235,235)"/></g><path d=" M 44.963 38.392 L 159.214 49.398 C 166.461 50.097 174.298 56.243 176.704 63.115 L 314.022 455.448 C 315.224 458.885 313.245 461.673 309.604 461.673 L 197.695 461.673 C 190.414 461.673 182.502 456.111 180.038 449.259 L 36.295 49.541 C 33.832 42.689 37.715 37.693 44.963 38.392 Z " fill="rgb(93,135,191)"/></g></svg>
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After Width: | Height: | Size: 1.9 KiB |
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After Width: | Height: | Size: 15 KiB |
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<html>
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<header>
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<title>@title</title>
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<meta charset="utf-8"/>
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@css 'assets/site.css'
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</header>
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<body>
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<h1>@title</h1>
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<button>Close the connection</button>
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<ul></ul>
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<script>
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"use strict";
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var button = document.querySelector('button');
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var eventList = document.querySelector('ul');
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const evtSource = new EventSource('/sse');
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evtSource.onerror = function() { console.log("EventSource failed."); };
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console.log(evtSource.withCredentials);
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console.log(evtSource.readyState);
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console.log(evtSource.url);
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evtSource.onopen = function() {
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console.log("Connection to server opened.");
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};
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evtSource.onmessage = function(e) {
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var newElement = document.createElement("li");
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newElement.textContent = "message: " + e.data;
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eventList.appendChild(newElement);
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};
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evtSource.addEventListener("ping", function(e) {
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console.log(e)
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var newElement = document.createElement("li");
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var obj = JSON.parse(e.data);
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newElement.innerHTML = "ping at " + obj.time + ' server data: ' + e.data;
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eventList.appendChild(newElement);
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}, false);
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button.onclick = function() { console.log('Connection closed'); evtSource.close(); };
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</script>
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</body>
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</html>
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@ -0,0 +1,38 @@
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module main
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import rand
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import time
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import vweb
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import vweb.sse
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struct App {
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vweb.Context
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}
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fn main() {
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vweb.run<App>(8081)
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}
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pub fn (mut app App) init_once() {
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app.serve_static('/favicon.ico', 'favicon.ico', 'img/x-icon')
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app.handle_static('.')
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}
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pub fn (mut app App) index() vweb.Result {
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title := 'SSE Example'
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return $vweb.html()
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}
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fn (mut app App) sse() vweb.Result {
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mut session := sse.new_connection(app.conn)
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// NB: you can setup session.write_timeout and session.headers here
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session.start() or { return app.server_error(501) }
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session.send_message(data: 'ok') or { return app.server_error(501) }
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for {
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data := '{"time": "$time.now().str()", "random_id": "$rand.ulid()"}'
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session.send_message(event: 'ping', data: data) or { return app.server_error(501) }
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println('> sent event: $data')
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time.sleep_ms(1000)
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}
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return app.server_error(501)
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}
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@ -0,0 +1,77 @@
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module sse
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import net
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import time
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import strings
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// This module implements the server side of `Server Sent Events`.
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// See https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events#event_stream_format
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// as well as https://html.spec.whatwg.org/multipage/server-sent-events.html#server-sent-events
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// for detailed description of the protocol, and a simple web browser client example.
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//
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// > Event stream format
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// > The event stream is a simple stream of text data which must be encoded using UTF-8.
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// > Messages in the event stream are separated by a pair of newline characters.
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// > A colon as the first character of a line is in essence a comment, and is ignored.
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// > Note: The comment line can be used to prevent connections from timing out;
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// > a server can send a comment periodically to keep the connection alive.
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// >
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// > Each message consists of one or more lines of text listing the fields for that message.
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// > Each field is represented by the field name, followed by a colon, followed by the text
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// > data for that field's value.
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[ref_only]
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pub struct SSEConnection {
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pub mut:
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headers map[string]string
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conn &net.TcpConn
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write_timeout time.Duration = 600 * time.second
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}
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pub struct SSEMessage {
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id string
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event string
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data string
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retry int
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}
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pub fn new_connection(conn &net.TcpConn) SSEConnection {
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return SSEConnection{
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conn: conn
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}
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}
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// sse_start is used to send the start of a Server Side Event response.
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pub fn (mut sse SSEConnection) start() ? {
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sse.conn.set_write_timeout(sse.write_timeout)
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mut start_sb := strings.new_builder(512)
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start_sb.write('HTTP/1.1 200')
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start_sb.write('\r\nConnection: keep-alive')
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start_sb.write('\r\nCache-Control: no-cache')
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start_sb.write('\r\nContent-Type: text/event-stream')
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for k, v in sse.headers {
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start_sb.write('\r\n$k: $v')
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}
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start_sb.write('\r\n')
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sse.conn.write(start_sb.buf) or { return error('could not start sse response') }
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}
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// send_message sends a single message to the http client that listens for SSE.
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// It does not close the connection, so you can use it many times in a loop.
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pub fn (mut sse SSEConnection) send_message(message SSEMessage) ? {
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mut sb := strings.new_builder(512)
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if message.id != '' {
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sb.write('id: $message.id\n')
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}
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if message.event != '' {
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sb.write('event: $message.event\n')
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}
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if message.data != '' {
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sb.write('data: $message.data\n')
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}
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if message.retry != 0 {
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sb.write('retry: $message.retry\n')
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}
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sb.write('\n')
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sse.conn.write(sb.buf) ?
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}
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@ -158,6 +158,17 @@ pub fn (mut ctx Context) ok(s string) Result {
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return Result{}
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}
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pub fn (mut ctx Context) server_error(ecode int) Result {
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$if debug {
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eprintln('> ctx.server_error ecode: $ecode')
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}
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if ctx.done {
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return Result{}
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}
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send_string(mut ctx.conn, vweb.http_500) or { }
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return Result{}
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}
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pub fn (mut ctx Context) redirect(url string) Result {
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if ctx.done {
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return Result{}
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@ -592,6 +603,7 @@ fn handle_conn<T>(mut conn net.TcpConn, mut app T) {
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// call action method
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if method.args.len == vars.len {
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app.$method(vars)
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return
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} else {
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eprintln('warning: uneven parameters count ($method.args.len) in `$method.name`, compared to the vweb route `$method.attrs` ($vars.len)')
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}
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