我想做什么:
我的问题是:
首先,看看这个简化的工作示例:
const { Subject, defer, interval, of} = rxjs;
const EventEmitter = EventEmitter3;
const emitter = new EventEmitter();
const subject = new Subject();
// The next lines mock a websocket server message listener, imagine this being present on server side
emitter.on("request", () => {
subject.next(`Immediate response`);
interval(1000).subscribe((index) =>
subject.next(`Delayed response...${index}`)
);
});
// Imagine the following code being present in the browser
function getData() {
return defer(() => {
// The next line mocks a websocket client sent event
setTimeout(() => emitter.emit("request"), 0);
return subject;
});
}
getData().subscribe((data) => console.log(data));
<script src="https://cdnjs.cloudflare.com/ajax/libs/rxjs/6.5.3/rxjs.umd.min.js"></script>
<script src="https://unpkg.com/eventemitter3@latest/umd/eventemitter3.min.js"></script>
现在看一个非工作示例。在这里,客户端不会立即得到响应,因为在设置订阅之前发送了 'request' 事件。
const { Subject, defer, interval, of} = rxjs;
const EventEmitter = EventEmitter3;
const emitter = new EventEmitter();
const subject = new Subject();
// The next lines mock a websocket server message listener, imagine this being present on server side
emitter.on("request", () => {
subject.next(`Immediate response`);
interval(1000).subscribe((index) =>
subject.next(`Delayed response...${index}`)
);
});
// Imagine the following code being present in the browser
function getData() {
return defer(() => {
emitter.emit('request');
return subject;
});
}
getData().subscribe((data) => console.log(data));
<script src="https://cdnjs.cloudflare.com/ajax/libs/rxjs/6.5.3/rxjs.umd.min.js"></script>
<script src="https://unpkg.com/eventemitter3@latest/umd/eventemitter3.min.js"></script>
答案 0 :(得分:2)
您可以使用 BehaviorSubject
而不是 Subject
:
const { BehaviorSubject, defer, interval, of } = rxjs;
const EventEmitter = EventEmitter3;
const emitter = new EventEmitter();
const subject = new BehaviorSubject();
// The next lines mock a websocket server message listener, imagine this being present on server side
emitter.on("request", () => {
// the timing of this synchronous response would be impossible in a real socket
subject.next(`Immediate response`);
interval(1000).subscribe((index) =>
subject.next(`Delayed response...${index}`)
);
});
// Imagine the following code being present in the browser
function getData() {
return defer(() => {
emitter.emit('request');
return subject;
});
}
getData().subscribe((data) => console.log(data));
<script src="https://cdnjs.cloudflare.com/ajax/libs/rxjs/6.5.3/rxjs.umd.min.js"></script>
<script src="https://unpkg.com/eventemitter3@latest/umd/eventemitter3.min.js"></script>
请记住,在发送套接字请求后,服务器的响应不可能同步返回,就像您为此演示实现模拟的方式一样,因此虽然 Subject
不会产生预期的结果在这里,它可以在真正的套接字上正常工作。