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Consider reseting property to default when binding undefined structured data #1946

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kevinpschaaf opened this issue Jun 24, 2015 · 1 comment
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Consider reseting property to default when binding undefined structured data #1946

kevinpschaaf opened this issue Jun 24, 2015 · 1 comment
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@kevinpschaaf
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When binding structured data (e.g. {{item.type}}) to an element, if a new item is assigned that no longer has a sub-property where the previous object did (e.g. item goes from {name: 'foo', type: 'zaz'} to {name: 'bar'}, an undefined value will be pushed through the binding to the element. Since undefined has special meaning, especially for multi-property observers which are not called until all properties are defined, this can result in unexpected state.

See use case at #1742 and proposed fix in #1941
@kevinpschaaf kevinpschaaf self-assigned this Jun 24, 2015
kevinpschaaf added a commit that referenced this issue Jun 24, 2015
@kevinpschaaf
Use single-property observer to deal better with if=undefined. Fixes #…
fd741bf 
…1742

This takes advantage of the fact that single property observers are called for each change (including undefined), whereas multi-property observers wait for all properties to be defined.  Since the side-effect of the observe is to queue an async render, there is no real benefit from this being a multi-property observer.  #1946 is open to track a more general fix for this issue.
This was referenced Jun 24, 2015
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Closing, we likely won't pursue this gambit as a solution.

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