39 lines
1.2 KiB
Markdown
39 lines
1.2 KiB
Markdown
# stream
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A `stream` is a [computed](./computed.md) that works asynchronously. Dependencies can be synchronous
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or asynchronous functions returning a scalar or a promise respectively. Also calling a stream
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multiple overlapping times will return the same promise and result (so long as dependencies do not
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change in the time gap). In this way, stream can serve as a temporal deduplicator.
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## Usage
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### Creation
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```js
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const getToken = stream(
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async tokenUrl => fetch(tokenUrl), // computation function
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[getTokenUrl, tokenTimeout] // array of subscribable dependencies
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);
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```
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### Read
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```js
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if (await getToken()) {
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/* do stuff with the token */
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}
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```
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### Provide a hash function for complex result types
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When the stream result is a type that is not determined to be equal with simple equality (===),
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provide a hash function to the `hashableStream` type to create a stream that will reduce the result
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value to a value that can be compared with the identity operator before comparison. The computed
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result value will still be stored unmodified.
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```js
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const tokenStream = hashableStream(token => token && token.id);
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const getToken = tokenStream(async tokenUrl => fetch(tokenUrl), [getTokenUrl]);
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```
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