conditional import for code base that is also used for mobile?

[jdeltoft]

I'm importing the html version like this:

import 'package:web_socket_channel/html.dart';

and then I'm using this call to create the channel:

        channel = HtmlWebSocketChannel.connect(
            'wss://my.domain.com:1234/ws');

But when I build for mobile, is there a way to condition this out? I am familiar with using kIsWeb for calls I only want on web, and I have one single code base before this above need to use websockets.

Am I doing something wrong?

[jdeltoft]

Flutter doctor -v:

[✓] Flutter (Channel beta, v1.17.0, on Mac OS X 10.14.6 18G3020, locale en-US)
• Flutter version 1.17.0 at /Users/jeltoft/flutter/flutter
• Framework revision d3ed9ec945 (3 weeks ago), 2020-04-06 14:07:34 -0700
• Engine revision c9506cb8e9
• Dart version 2.8.0 (build 2.8.0-dev.18.0 eea9717938)

[✓] Android toolchain - develop for Android devices (Android SDK version 28.0.3)
• Android SDK at /Users/jeltoft/Library/Android/sdk
• Platform android-28, build-tools 28.0.3
• Java binary at: /Applications/Android Studio.app/Contents/jre/jdk/Contents/Home/bin/java
• Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b4-5784211)
• All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 11.3.1)
• Xcode at /Applications/Xcode.app/Contents/Developer
• Xcode 11.3.1, Build version 11C504
• CocoaPods version 1.9.1

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[✓] Android Studio (version 3.6)
• Android Studio at /Applications/Android Studio.app/Contents
• Flutter plugin version 45.1.1
• Dart plugin version 192.7761
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[✓] Connected device (3 available)
• SM G965U • 3555453044323098 • android-arm64 • Android 10 (API 29)
• Chrome • chrome • web-javascript • Google Chrome 81.0.4044.122
• Web Server • web-server • web-javascript • Flutter Tools

• No issues found!

Error starts like this:

Compiler message:
../../flutter/flutter/.pub-cache/hosted/pub.dartlang.org/web_socket_channel-1.1.0/lib/html.dart:8:8: Error: Not found: 'dart:html'
import 'dart:html';
^
../../flutter/flutter/.pub-cache/hosted/pub.dartlang.org/web_socket_channel-1.1.0/lib/html.dart:21:9: Error: Type 'WebSocket' not found.
final WebSocket _webSocket;
^^^^^^^^^
../../flutter/flutter/.pub-cache/hosted/pub.dartlang.org/web_socket_channel-1.1.0/lib/html.dart:21:9: Error: 'WebSocket' isn't a type.
final WebSocket _webSocket;
^^^^^^^^^
../../flutter/flutter/.pub-cache/hosted/pub.dartlang.org/web_socket_channel-1.1.0/lib/html.dart:67:14: Error: The method 'WebSocket' isn't defined for the class 'HtmlWebSocketChannel'.

• 'HtmlWebSocketChannel' is from 'package:web_socket_channel/html.dart' ('../../flutter/flutter/.pub-cache/hosted/pub.dartlang.org/web_socket_channel-1.1.0/lib/html.dart').
  Try correcting the name to the name of an existing method, or defining a method named 'WebSocket'.
  : this(WebSocket(url.toString(), protocols)
  ^^^^^^^^^
  ../../flutter/flutter/.pub-cache/hosted/pub.dartlang.org/web_socket_channel-1.1.0/lib/html.dart:74:34: Error: The getter 'WebSocket' isn't defined for the class 'HtmlWebSocketChannel'.
• 'HtmlWebSocketChannel' is from 'package:web_socket_channel/html.dart' ('../../flutter/flutter/.pub-cache/hosted/pub.dartlang.org/web_socket_channel-1.1.0/lib/html.dart').
  Try correcting the name to the name of an existing getter, or defining a getter or field named 'WebSocket'.
  if (_webSocket.readyState == WebSocket.OPEN) {
  ^^^^^^^^^

[natebosch]

You can conditionally switch an import from one URI to another, but you can't conditionally change any code. HtmlWebSocketChannel.connect will never work outside the web.

Luckily there is WebSocketChannel.connect which handles picking the correct behavior on web vs IO. You should be able to switch you import from package:web_socket_channel/html.dart to package:web_socket_channel/web_socket_channel.dart and change HtmlWebSocketChannel to WebSocketChannel.

[jdeltoft]

@natebosch thanks!! I needed to add URI.parse() around the input string. Perfect.