blocks|key|760973|text|创建新的流，它释放当前的价值，并倾听该流是我的最佳实践。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|760974|class+FormBloc+{
++final+BehaviorSubject<bool>+_result+=+BehaviorSubject();
++final+BehaviorSubject<String?>+_usernameController+=+BehaviorSubject();
++final+BehaviorSubject<String?>+_emailController+=+BehaviorSubject();

++final+_usernameStreamController+=+StreamController<String?>()
++++..add(_usernameController.value)
++++..addStream(_usernameController.stream);
++final+_emailStreamController+=+StreamController<String?>()
++++..add(_emailController.value)
++++..addStream(_emailController.stream);

++Stream<bool>+get+valid$+=>+Rx.combineLatest2(
++++_usernameStreamController.stream,++//+use+streamController+instead
++++_emailStreamController.stream,++//+use+streamController+instead
++++(username,+email)+=>+username+!=+null+%7C%7C+email+!=+null
++);
}|code-block|syntax|javascript|760975|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Creating new stream which emits current value and listen the stream is my best practice.
<pre class="lang-dart prettyprint-override"><code>class FormBloc {
 final BehaviorSubject&lt;bool&gt; _result = BehaviorSubject();
 final BehaviorSubject&lt;String?&gt; _usernameController = BehaviorSubject();
 final BehaviorSubject&lt;String?&gt; _emailController = BehaviorSubject();

 final _usernameStreamController = StreamController&lt;String?&gt;()
 ..add(_usernameController.value)
 ..addStream(_usernameController.stream);
 final _emailStreamController = StreamController&lt;String?&gt;()
 ..add(_emailController.value)
 ..addStream(_emailController.stream);

 Stream&lt;bool&gt; get valid$ =&gt; Rx.combineLatest2(
 _usernameStreamController.stream, // use streamController instead
 _emailStreamController.stream, // use streamController instead
 (username, email) =&gt; username != null || email != null
 );
}
</code></pre>

blocks|key|1890355|text|您可以使用一个BehaviorSubject<Map<String,+String?>>来发出用户名或电子邮件中的更改，而不是组合多个流。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1890356|add要么更改\提交的用户名，要么向BehaviorSubject发送电子邮件|1890357|_usernameEmailController.add({"uname":+value},);|code-block|syntax|javascript|1890358|或|1890359|_usernameEmailController.add({"email":+value},);|1890360|这样您就可以通过侦听来验证输入。我使用StreamBuilder来显示发出的值，|1890361|++++++++++++StreamBuilder<Map<String,+String?>>(
++++++++++++++stream:+_usernameEmailController.stream
++++++++++++++++++.map((data)+{
++++++++++++++++++++_r+=+{..._r,+...data};
++++++++++++++++++++return+_r;
++++++++++++++++++}),
++++++++++++++builder:+(context,+snapshot)+{
++++++++++++++++return+Column(
++++++++++++++++++children:+[
++++++++++++++++++++Text(snapshot.data.toString()),
++++++++++++++++++++if+(snapshot.hasData)
++++++++++++++++++++++Text(
++++++++++++++++++++++++++"Is+valid?:+"
++++++++++++++++++++++++++"${(snapshot.data!["uname"]+!=+null+&&+snapshot.data!["uname"]!.isNotEmpty)+%7C%7C+(snapshot.data!["email"]+!=+null+&&+snapshot.data!["email"]!.isNotEmpty)}"
++++++++++++++++++++++),
++++++++++++++++++],
++++++++++++++++);
++++++++++++++},
++++++++++++),|1890362|在DartPad+这里上查看我的解决方案。|1890363|在DartPad中，我使用了StreamController而不是BehaviorSubject，因为DartPad不支持rxdart包。但是您可以在DartPad中替换第40行|1890364|final+StreamController<Map<String,+String?>>+_usernameEmailController+=
++++++++StreamController();|1890365|使用|1890366|final+BehaviorSubject<Map<String,+String?>>+_usernameEmailController+=
++++++++BehaviorSubject();|1890367|如果您想使用BehaviorSubject。|1890368|entityMap|0|LINK|mutability|MUTABLE|url|https://pub.dev/documentation/rxdart/latest/rx/Subject/add.html|1|https://dartpad.dev/?id=9aceb01992dd187469643877aa0e3a28^0|7|11|0|0|3|I|F|0|3|0|0|0|0|0|J|D|0|0|9|2|1|0|E|G|X|F|1P|6|0|0|0|0|6|F|0^^$0|@$1|2|3|4|5|6|7|1G|8|@$9|1H|A|1I|B|C]]|D|@]|E|$]]|$1|F|3|G|5|6|7|1J|8|@$9|1K|A|1L|B|C]|$9|1M|A|1N|B|C]]|D|@$9|1O|A|1P|1|1Q]]|E|$]]|$1|H|3|I|5|J|7|1R|8|@]|D|@]|E|$K|L]]|$1|M|3|N|5|6|7|1S|8|@]|D|@]|E|$]]|$1|O|3|P|5|J|7|1T|8|@]|D|@]|E|$K|L]]|$1|Q|3|R|5|6|7|1U|8|@$9|1V|A|1W|B|C]]|D|@]|E|$]]|$1|S|3|T|5|J|7|1X|8|@]|D|@]|E|$K|L]]|$1|U|3|V|5|6|7|1Y|8|@]|D|@$9|1Z|A|20|1|21]]|E|$]]|$1|W|3|X|5|6|7|22|8|@$9|23|A|24|B|C]|$9|25|A|26|B|C]|$9|27|A|28|B|C]]|D|@]|E|$]]|$1|Y|3|Z|5|J|7|29|8|@]|D|@]|E|$K|L]]|$1|10|3|11|5|6|7|2A|8|@]|D|@]|E|$]]|$1|12|3|13|5|J|7|2B|8|@]|D|@]|E|$K|L]]|$1|14|3|15|5|6|7|2C|8|@$9|2D|A|2E|B|C]]|D|@]|E|$]]|$1|16|3|-4|5|6|7|2F|8|@]|D|@]|E|$]]]|17|$18|$5|19|1A|1B|E|$1C|1D]]|1E|$5|19|1A|1B|E|$1C|1F]]]]

Instead of combining multiple streams, you can use one <code>BehaviorSubject&lt;Map&lt;String, String?&gt;&gt;</code> to emit changes in username or email.
<a href="https://pub.dev/documentation/rxdart/latest/rx/Subject/add.html" rel="nofollow noreferrer"><code>add</code></a> either changed\submitted username or email to the <code>BehaviorSubject</code>
<pre class="lang-dart prettyprint-override"><code>_usernameEmailController.add({&quot;uname&quot;: value},);
</code></pre>
or
<pre class="lang-dart prettyprint-override"><code>_usernameEmailController.add({&quot;email&quot;: value},);
</code></pre>
so that you can validate the inputs by listening to it. I used <code>StreamBuilder</code> to display the emitted values,
<pre class="lang-dart prettyprint-override"><code> StreamBuilder&lt;Map&lt;String, String?&gt;&gt;(
 stream: _usernameEmailController.stream
 .map((data) {
 _r = {..._r, ...data};
 return _r;
 }),
 builder: (context, snapshot) {
 return Column(
 children: [
 Text(snapshot.data.toString()),
 if (snapshot.hasData)
 Text(
 &quot;Is valid?: &quot;
 &quot;${(snapshot.data![&quot;uname&quot;] != null &amp;&amp; snapshot.data![&quot;uname&quot;]!.isNotEmpty) || (snapshot.data![&quot;email&quot;] != null &amp;&amp; snapshot.data![&quot;email&quot;]!.isNotEmpty)}&quot;
 ),
 ],
 );
 },
 ),

</code></pre>
checkout the my solution on DartPad <a href="https://dartpad.dev/?id=9aceb01992dd187469643877aa0e3a28" rel="nofollow noreferrer">here</a>.
In the DartPad I have used <code>StreamController</code> instead of <code>BehaviorSubject</code> as DartPad doesn't support <code>rxdart</code> Package.
But you can replace line 40 in DartPad
<pre class="lang-dart prettyprint-override"><code>final StreamController&lt;Map&lt;String, String?&gt;&gt; _usernameEmailController =
 StreamController();
</code></pre>
with
<pre class="lang-dart prettyprint-override"><code>final BehaviorSubject&lt;Map&lt;String, String?&gt;&gt; _usernameEmailController =
 BehaviorSubject();
</code></pre>
If you want to use <code>BehaviorSubject</code>.

blocks|key|1890375|text|您可以将默认值为null作为BehaviorSubjects的种子：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1890376|++final+BehaviorSubject<String?>+_usernameController+=+BehaviorSubject().seeded(null);
++final+BehaviorSubject<String?>+_emailController+=+BehaviorSubject().seeded(null);|code-block|syntax|javascript|1890377|另一种可能是给合并的流一个种子值：|1890378|Rx.combineLatest2(
++++_usernameController.stream,+
++++_emailController.stream,+
++++(username,+email)+=>+username+!=+null+%7C%7C+email+!=+null
++).sharedValueSeeded(false);|1890379|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

You could seed your BehaviorSubjects with a default value of null:
<pre><code> final BehaviorSubject&lt;String?&gt; _usernameController = BehaviorSubject().seeded(null);
 final BehaviorSubject&lt;String?&gt; _emailController = BehaviorSubject().seeded(null);
</code></pre>
Another possibility would be to give the combined stream a seed value:
<pre><code>Rx.combineLatest2(
 _usernameController.stream, 
 _emailController.stream, 
 (username, email) =&gt; username != null || email != null
 ).sharedValueSeeded(false);
</code></pre>

blocks|key|763807|text|因为这里的所有解决方案都是解决方案，所以我实现了自己的流类。实现等于原始的CombineLatestStream实现，只是它不等待所有流发出后才发出：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|763808|import+'dart:async';

import+'package:rxdart/src/utils/collection_extensions.dart';
import+'package:rxdart/src/utils/subscription.dart';

class+CombineAnyLatestStream<T,+R>+extends+StreamView<R>+{

++CombineAnyLatestStream(List<Stream<T>>+streams,+R+Function(List<T?>)+combiner)+:+super(_buildController(streams,+combiner).stream);

++static+StreamController<R>+_buildController<T,+R>(
++++Iterable<Stream<T>>+streams,
++++R+Function(List<T?>+values)+combiner,
++)+{

++++int+completed+=+0;

++++late+List<StreamSubscription<T>>+subscriptions;
++++List<T?>?+values;

++++final+_controller+=+StreamController<R>(sync:+true);

++++_controller.onListen+=+()+{

++++++void+onDone()+{
++++++++if+(%2B%2Bcompleted+==+streams.length)+{
++++++++++_controller.close();
++++++++}
++++++}

++++++subscriptions+=+streams.mapIndexed((index,+stream)+{

++++++++return+stream.listen(
++++++++++(T+event)+{
++++++++++++final+R+combined;

++++++++++++if+(values+==+null)+return;

++++++++++++values![index]+=+event;

++++++++++++try+{
++++++++++++++combined+=+combiner(List<T?>.unmodifiable(values!));
++++++++++++}+catch+(e,+s)+{
++++++++++++++_controller.addError(e,+s);
++++++++++++++return;
++++++++++++}

++++++++++++_controller.add(combined);
++++++++++},
++++++++++onError:+_controller.addError,
++++++++++onDone:+onDone
++++++++);
++++++}).toList(growable:+false);

++++++if+(subscriptions.isEmpty)+{
++++++++_controller.close();
++++++}+else+{
++++++++values+=+List<T?>.filled(subscriptions.length,+null);
++++++}
++++};

++++_controller.onPause+=+()+=>+subscriptions.pauseAll();
++++_controller.onResume+=+()+=>+subscriptions.resumeAll();
++++_controller.onCancel+=+()+{
++++++values+=+null;
++++++return+subscriptions.cancelAll();
++++};

++++return+_controller;
++}

}|code-block|syntax|javascript|763809|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Because all of the solutions here are workarounds Ive implemented my own stream class. Implementation equals the original CombineLatestStream implementation except that it does not wait for all streams to emit before emitting:
<pre class="lang-dart prettyprint-override"><code>
import 'dart:async';

import 'package:rxdart/src/utils/collection_extensions.dart';
import 'package:rxdart/src/utils/subscription.dart';

class CombineAnyLatestStream&lt;T, R&gt; extends StreamView&lt;R&gt; {

 CombineAnyLatestStream(List&lt;Stream&lt;T&gt;&gt; streams, R Function(List&lt;T?&gt;) combiner) : super(_buildController(streams, combiner).stream);

 static StreamController&lt;R&gt; _buildController&lt;T, R&gt;(
 Iterable&lt;Stream&lt;T&gt;&gt; streams,
 R Function(List&lt;T?&gt; values) combiner,
 ) {

 int completed = 0;

 late List&lt;StreamSubscription&lt;T&gt;&gt; subscriptions;
 List&lt;T?&gt;? values;

 final _controller = StreamController&lt;R&gt;(sync: true);

 _controller.onListen = () {

 void onDone() {
 if (++completed == streams.length) {
 _controller.close();
 }
 }

 subscriptions = streams.mapIndexed((index, stream) {

 return stream.listen(
 (T event) {
 final R combined;

 if (values == null) return;

 values![index] = event;

 try {
 combined = combiner(List&lt;T?&gt;.unmodifiable(values!));
 } catch (e, s) {
 _controller.addError(e, s);
 return;
 }

 _controller.add(combined);
 },
 onError: _controller.addError,
 onDone: onDone
 );
 }).toList(growable: false);

 if (subscriptions.isEmpty) {
 _controller.close();
 } else {
 values = List&lt;T?&gt;.filled(subscriptions.length, null);
 }
 };

 _controller.onPause = () =&gt; subscriptions.pauseAll();
 _controller.onResume = () =&gt; subscriptions.resumeAll();
 _controller.onCancel = () {
 values = null;
 return subscriptions.cancelAll();
 };

 return _controller;
 }

}
</code></pre>

In RX dart there is the <a href="https://pub.dev/documentation/rxdart/latest/rx/CombineLatestStream-class.html" rel="nofollow noreferrer"><code>RX.combineLatest</code></a> method to combine the results of a stream using a callback function.
Problem is that it only emits a value when every stream has emitted a value. If one has not it does not emit.
<blockquote>
Merges the given Streams into a single Stream sequence by using the combiner function whenever any of the stream sequences emits an item.
The Stream will not emit until all streams have emitted at least one item.
</blockquote>
Im trying to combine multiple streams into one stream for validation which should emit false or true when the streams have not emitted or emitted an empty value.
<pre class="lang-dart prettyprint-override"><code>class FormBloc {
 final BehaviorSubject&lt;bool&gt; _result = BehaviorSubject();
 final BehaviorSubject&lt;String?&gt; _usernameController = BehaviorSubject();
 final BehaviorSubject&lt;String?&gt; _emailController = BehaviorSubject();

 // Will only emit if each stream emitted a value
 // If only username is emitted valid is not emitted
 Stream&lt;bool&gt; get valid$ =&gt; Rx.combineLatest2(
 _usernameController.stream, 
 _emailController.stream, 
 (username, email) =&gt; username != null || email != null
 );

}

</code></pre>
How can I join those streams so <code>valid$</code> emits a value if any of the streams change?

rx dart combine multiple streams to emit value whenever any of the streams emit a value

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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在RX中，有一个使用回调函数组合流结果的方法。问题是，只有当每个流发出一个值时，它才会发出一个值。如果一个人没有，它就不会发出。每当任何流序列发出项时，通过使用组合器函数将给定的流合并成单个流序列。在所有流至少发出一项之后，流才会发出。Im试图将多个流合并到一个流中进行验证，当流没有发出或发出空值时，应该发出false...

问每当任何流发出值时，rx dart都会组合多个流来发出值。
EN

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问每当任何流发出值时，rx dart都会组合多个流来发出值。EN