Dart Streams StreamTransformer int上的错误不是EventSink的子类型<;动态>;
尝试学习Dart和泛型现在我有了这个代码尝试学习关于流的知识,但我似乎明白我的代码有什么问题Dart Streams StreamTransformer int上的错误不是EventSink的子类型<;动态>;,dart,Dart,尝试学习Dart和泛型现在我有了这个代码尝试学习关于流的知识,但我似乎明白我的代码有什么问题 import 'dart:async'; void main() { StreamController<int> controller = new StreamController<int>(); num i = 0; Future.doWhile(() { controller.add(i++); if (i == 100) {
import 'dart:async';
void main() {
StreamController<int> controller = new StreamController<int>();
num i = 0;
Future.doWhile(() {
controller.add(i++);
if (i == 100) {
return false;
}
return true;
});
var result = controller.stream.transform(
StreamTransformer<int, EventSink<dynamic>>.fromHandlers(
handleData: (int number, EventSink<dynamic> sink) {
if (number == 70) {
sink.addError("Hit seventy");
} else {
sink.add(number);
}
}));
result.listen((data) => print(data));
}
导入'dart:async';
void main(){
StreamController=新的StreamController();
numi=0;
Future.doWhile(){
controller.add(i++);
如果(i==100){
返回false;
}
返回true;
});
var结果=controller.stream.transform(
StreamTransformer.fromHandlers(
handleData:(整数,事件接收器){
如果(数字=70){
下沉。加法器(“命中70”);
}否则{
增加(数字);
}
}));
结果.监听((数据)=>打印(数据));
}
上面的代码给我带来了以下错误
type 'int' is not a subtype of type 'EventSink<dynamic>' of 'data'
EventSinkWrapper.add (dart:async/stream_transformers.dart)
main.<anonymous closure> (file:///var/www/html/learning/dart/rr.dart:23:12)
HandlerEventSink.add (dart:async/stream_transformers.dart:228:7)
SinkTransformerStreamSubscription._handleData (dart:async/stream_transformers.dart:120:24)
类型“int”不是“data”的“EventSink”类型的子类型
EventSinkWrapper.add(dart:async/stream\u transformers.dart)
梅因。(file:///var/www/html/learning/dart/rr.dart:23:12)
HandlerEventSink.add(dart:async/stream\u transformers.dart:228:7)
SinkTransformersStreamSubscription.\u handleData(dart:async/stream\u transformers.dart:120:24)
AStreamTransformer
的通用类型是数据输入类型和数据输出类型。您的转换器将int
映射到dynamic
(不过,正如当前编写的,它实际上只发出int
)
您在StringTransformer
构造函数上的类型不正确。(此外,无需重复handleData
lambda定义中的类型,因为它们可以从变压器的类型推断出来。)
尝试:
void main(){
StreamController=新的StreamController();
numi=0;
Future.doWhile(){
controller.add(i++);
返回i<100;
});
var结果=controller.stream.transform(
StreamTransformer.fromHandlers(
handleData:(数字,水槽){
如果(数字=70){
下沉。加法器(“命中70”);
}否则{
增加(数字);
}
},
),
);
结果.监听((数据)=>打印(数据));
}
void main() {
StreamController<int> controller = new StreamController<int>();
num i = 0;
Future.doWhile(() {
controller.add(i++);
return i < 100;
});
var result = controller.stream.transform(
StreamTransformer<int, dynamic>.fromHandlers(
handleData: (number, sink) {
if (number == 70) {
sink.addError("Hit seventy");
} else {
sink.add(number);
}
},
),
);
result.listen((data) => print(data));
}