34 lines
1004 B
Markdown
34 lines
1004 B
Markdown
Cursors
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-------
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Cursors allow you to hold a reference to a path in a nested immutable data
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structure, allowing you to pass smaller sections of a larger nested
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collection to portions of your application while maintaining a central point
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aware of changes to the entire data structure: an `onChange` function which is
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called whenever a cursor or sub-cursor calls `update`.
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This is particularly useful when used in conjuction with component-based UI
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libraries like [React](http://facebook.github.io/react/) or to simulate
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"state" throughout an application while maintaining a single flow of logic.
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```javascript
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var Immutable = require('immutable');
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var Cursor = require('immutable/contrib/cursor');
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var data = Immutable.fromJS({ a: { b: { c: 1 } } });
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var cursor = Cursor.from(data, ['a', 'b'], newData => {
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data = newData;
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});
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// ... elsewhere ...
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cursor.get('c'); // 1
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cursor = cursor.update('c', x => x + 1);
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cursor.get('c'); // 2
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// ... back to data ...
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data.getIn(['a', 'b', 'c']); // 2
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```
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