Repositorio del curso CCOM4030 el semestre B91 del proyecto Artesanías con el Instituto de Cultura

webSocket.d.ts 9.9KB

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  1. import { WebSocketSubject, WebSocketSubjectConfig } from './WebSocketSubject';
  2. /**
  3. * Wrapper around the w3c-compatible WebSocket object provided by the browser.
  4. *
  5. * <span class="informal">{@link Subject} that communicates with a server via WebSocket</span>
  6. *
  7. * `webSocket` is a factory function that produces a `WebSocketSubject`,
  8. * which can be used to make WebSocket connection with an arbitrary endpoint.
  9. * `webSocket` accepts as an argument either a string with url of WebSocket endpoint, or an
  10. * {@link WebSocketSubjectConfig} object for providing additional configuration, as
  11. * well as Observers for tracking lifecycle of WebSocket connection.
  12. *
  13. * When `WebSocketSubject` is subscribed, it attempts to make a socket connection,
  14. * unless there is one made already. This means that many subscribers will always listen
  15. * on the same socket, thus saving resources. If however, two instances are made of `WebSocketSubject`,
  16. * even if these two were provided with the same url, they will attempt to make separate
  17. * connections. When consumer of a `WebSocketSubject` unsubscribes, socket connection is closed,
  18. * only if there are no more subscribers still listening. If after some time a consumer starts
  19. * subscribing again, connection is reestablished.
  20. *
  21. * Once connection is made, whenever a new message comes from the server, `WebSocketSubject` will emit that
  22. * message as a value in the stream. By default, a message from the socket is parsed via `JSON.parse`. If you
  23. * want to customize how deserialization is handled (if at all), you can provide custom `resultSelector`
  24. * function in {@link WebSocketSubject}. When connection closes, stream will complete, provided it happened without
  25. * any errors. If at any point (starting, maintaining or closing a connection) there is an error,
  26. * stream will also error with whatever WebSocket API has thrown.
  27. *
  28. * By virtue of being a {@link Subject}, `WebSocketSubject` allows for receiving and sending messages from the server. In order
  29. * to communicate with a connected endpoint, use `next`, `error` and `complete` methods. `next` sends a value to the server, so bear in mind
  30. * that this value will not be serialized beforehand. Because of This, `JSON.stringify` will have to be called on a value by hand,
  31. * before calling `next` with a result. Note also that if at the moment of nexting value
  32. * there is no socket connection (for example no one is subscribing), those values will be buffered, and sent when connection
  33. * is finally established. `complete` method closes socket connection. `error` does the same,
  34. * as well as notifying the server that something went wrong via status code and string with details of what happened.
  35. * Since status code is required in WebSocket API, `WebSocketSubject` does not allow, like regular `Subject`,
  36. * arbitrary values being passed to the `error` method. It needs to be called with an object that has `code`
  37. * property with status code number and optional `reason` property with string describing details
  38. * of an error.
  39. *
  40. * Calling `next` does not affect subscribers of `WebSocketSubject` - they have no
  41. * information that something was sent to the server (unless of course the server
  42. * responds somehow to a message). On the other hand, since calling `complete` triggers
  43. * an attempt to close socket connection. If that connection is closed without any errors, stream will
  44. * complete, thus notifying all subscribers. And since calling `error` closes
  45. * socket connection as well, just with a different status code for the server, if closing itself proceeds
  46. * without errors, subscribed Observable will not error, as one might expect, but complete as usual. In both cases
  47. * (calling `complete` or `error`), if process of closing socket connection results in some errors, *then* stream
  48. * will error.
  49. *
  50. * **Multiplexing**
  51. *
  52. * `WebSocketSubject` has an additional operator, not found in other Subjects. It is called `multiplex` and it is
  53. * used to simulate opening several socket connections, while in reality maintaining only one.
  54. * For example, an application has both chat panel and real-time notifications about sport news. Since these are two distinct functions,
  55. * it would make sense to have two separate connections for each. Perhaps there could even be two separate services with WebSocket
  56. * endpoints, running on separate machines with only GUI combining them together. Having a socket connection
  57. * for each functionality could become too resource expensive. It is a common pattern to have single
  58. * WebSocket endpoint that acts as a gateway for the other services (in this case chat and sport news services).
  59. * Even though there is a single connection in a client app, having the ability to manipulate streams as if it
  60. * were two separate sockets is desirable. This eliminates manually registering and unregistering in a gateway for
  61. * given service and filter out messages of interest. This is exactly what `multiplex` method is for.
  62. *
  63. * Method accepts three parameters. First two are functions returning subscription and unsubscription messages
  64. * respectively. These are messages that will be sent to the server, whenever consumer of resulting Observable
  65. * subscribes and unsubscribes. Server can use them to verify that some kind of messages should start or stop
  66. * being forwarded to the client. In case of the above example application, after getting subscription message with proper identifier,
  67. * gateway server can decide that it should connect to real sport news service and start forwarding messages from it.
  68. * Note that both messages will be sent as returned by the functions, they are by default serialized using JSON.stringify, just
  69. * as messages pushed via `next`. Also bear in mind that these messages will be sent on *every* subscription and
  70. * unsubscription. This is potentially dangerous, because one consumer of an Observable may unsubscribe and the server
  71. * might stop sending messages, since it got unsubscription message. This needs to be handled
  72. * on the server or using {@link publish} on a Observable returned from 'multiplex'.
  73. *
  74. * Last argument to `multiplex` is a `messageFilter` function which should return a boolean. It is used to filter out messages
  75. * sent by the server to only those that belong to simulated WebSocket stream. For example, server might mark these
  76. * messages with some kind of string identifier on a message object and `messageFilter` would return `true`
  77. * if there is such identifier on an object emitted by the socket. Messages which returns `false` in `messageFilter` are simply skipped,
  78. * and are not passed down the stream.
  79. *
  80. * Return value of `multiplex` is an Observable with messages incoming from emulated socket connection. Note that this
  81. * is not a `WebSocketSubject`, so calling `next` or `multiplex` again will fail. For pushing values to the
  82. * server, use root `WebSocketSubject`.
  83. *
  84. * ### Examples
  85. * #### Listening for messages from the server
  86. * ```ts
  87. * import { webSocket } from "rxjs/webSocket";
  88. * const subject = webSocket("ws://localhost:8081");
  89. *
  90. * subject.subscribe(
  91. * msg => console.log('message received: ' + msg), // Called whenever there is a message from the server.
  92. * err => console.log(err), // Called if at any point WebSocket API signals some kind of error.
  93. * () => console.log('complete') // Called when connection is closed (for whatever reason).
  94. * );
  95. * ```
  96. *
  97. * #### Pushing messages to the server
  98. * ```ts
  99. * import { webSocket } from "rxjs/webSocket";
  100. * const subject = webSocket('ws://localhost:8081');
  101. *
  102. * subject.subscribe();
  103. * // Note that at least one consumer has to subscribe to the created subject - otherwise "nexted" values will be just buffered and not sent,
  104. * // since no connection was established!
  105. *
  106. * subject.next({message: 'some message'});
  107. * // This will send a message to the server once a connection is made. Remember value is serialized with JSON.stringify by default!
  108. *
  109. * subject.complete(); // Closes the connection.
  110. *
  111. * subject.error({code: 4000, reason: 'I think our app just broke!'});
  112. * // Also closes the connection, but let's the server know that this closing is caused by some error.
  113. * ```
  114. *
  115. * #### Multiplexing WebSocket
  116. * ```ts
  117. * import { webSocket } from "rxjs/webSocket";
  118. * const subject = webSocket('ws://localhost:8081');
  119. *
  120. * const observableA = subject.multiplex(
  121. * () => ({subscribe: 'A'}), // When server gets this message, it will start sending messages for 'A'...
  122. * () => ({unsubscribe: 'A'}), // ...and when gets this one, it will stop.
  123. * message => message.type === 'A' // If the function returns `true` message is passed down the stream. Skipped if the function returns false.
  124. * );
  125. *
  126. * const observableB = subject.multiplex( // And the same goes for 'B'.
  127. * () => ({subscribe: 'B'}),
  128. * () => ({unsubscribe: 'B'}),
  129. * message => message.type === 'B'
  130. * );
  131. *
  132. * const subA = observableA.subscribe(messageForA => console.log(messageForA));
  133. * // At this moment WebSocket connection is established. Server gets '{"subscribe": "A"}' message and starts sending messages for 'A',
  134. * // which we log here.
  135. *
  136. * const subB = observableB.subscribe(messageForB => console.log(messageForB));
  137. * // Since we already have a connection, we just send '{"subscribe": "B"}' message to the server. It starts sending messages for 'B',
  138. * // which we log here.
  139. *
  140. * subB.unsubscribe();
  141. * // Message '{"unsubscribe": "B"}' is sent to the server, which stops sending 'B' messages.
  142. *
  143. * subA.unsubscribe();
  144. * // Message '{"unsubscribe": "A"}' makes the server stop sending messages for 'A'. Since there is no more subscribers to root Subject,
  145. * // socket connection closes.
  146. * ```
  147. *
  148. *
  149. * @param {string|WebSocketSubjectConfig} urlConfigOrSource The WebSocket endpoint as an url or an object with
  150. * configuration and additional Observers.
  151. * @return {WebSocketSubject} Subject which allows to both send and receive messages via WebSocket connection.
  152. */
  153. export declare function webSocket<T>(urlConfigOrSource: string | WebSocketSubjectConfig<T>): WebSocketSubject<T>;