當事件在另一個可觀察者中發生時，從一個可觀察者中檢索值

Question

假設我有兩個流。

• 價值觀
• buttonPresses

每次值更改時，我都會在值流中獲取該值。

每次按下按鈕時，都會在按鈕流中收到一個事件。

當我在buttonPresses流中獲得一個事件時，我想做些什么，並在值流中使用最新的值。 例如，進行API調用。

但是，我不希望每次值更改時都會發生任何事情。

我認為這是一個“可觀察的思維”問題。 這是我正在努力的實際代碼。

/**
 * Provides a stream of POSTCODE_LOOKUP action events
 * @type {Object}
 */
export let PostcodeLookupActionsStream = Actions.stream
    .filter( action => action.key === KEYS.POSTCODE_LOOKUP );

/**
 * Provides a stream of values from a post code input field.
 * @type {Object}
 */
export let PostCodeValueStream = Actions.stream
    .filter( action => action.key === KEYS.POSTCODE_CHANGE )
    .map( action => action.payload.postcode )
    .shareReplay(1);

// Combine the two streams....?
export let PostCodeLookupStream = Rx.Observable
    .merge(PostCodeValueStream, PostcodeLookupActionsStream)
    .map( (value, action) => value);

/**
 * Provides a stream of address retrieved from a postcode lookup
 * @type {Array}
 */
export let AddressStream = PostCodeLookupStream
    .flatMapLatest( postcode =>  MyAPI.postcodeLookup( postcode ) )
    .flatMap( response => response.json() )
    .shareReplay(1);

Answer 1

答案是使用withLatestFrom 。 我不知道為什么要花這么長時間在文檔中找到它，但是確實做到了。

/**
 * Provides a stream of POSTCODE_LOOKUP events
 * e.g: A stream of postcodes.
 * @type {Object} a mouse event
 */
export let PostcodeLookupIntentsStream = Actions.stream
    .filter( action => action.key === KEYS.POSTCODE_LOOKUP );

/**
 * Provides a stream of values from a  post code input field
 * @type {String}
 */
export let PostCodeValueStream = Actions.stream
    .filter( action => action.key === KEYS.POSTCODE_CHANGE )
    .map( action => action.payload.postcode )
    .shareReplay(1);


/**
 * Combines `PostcodeLookupIntentsStream` and `PostCodeValueStream` to
 * produce a stream of postcode values. New postcode values are emitted
 * every time an event is emitted from the            
 * `PostcodeLookupIntentsStream`
 */
export let PostCodeLookupValueStream = PostcodeLookupIntentsStream
    .withLatestFrom( PostCodeValueStream, (action, value) => value  );


/**
 * Provides a stream of address retrieved from a postcode lookup
 * @type {Array}
 */
export let AddressStream = PostCodeLookupStream
    .flatMapLatest( postcode => return MyAPI.postcodeLookup( postcode ) )
    .flatMap( response => response.json() )
    .shareReplay(1);