Retain loops are way too easy with block/closures but could be prevented in Swift

Originator:raylillywhite
Number:rdar://23238038 Date Originated:23-Oct-2015 11:16 AM
Status:Open Resolved:
Product:Developer Tools Product Version:
Classification: Reproducible:
 
Summary:
Retain loops are by far the number one reason for memory leaks, but a simple feature of Swift could almost completely eliminate them:

Require the ownership of `self` to be explicitly specified in a block unless the block is only used for a `@noescape` block.

Developers very rarely mistakenly choose to have `self` strongly retained to create the retain loops. Usually it's because we go back and modify something within a block and we use self without thinking about the capture semantics, or because we forgot to specify while we're writing the code.

Having to explicitly type `[strong self]` would probably eliminate more than 90% of retain loops in most applications. I know that's a breaking change, but hopefully the code migrator would be able to handle making that transition easier.

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Version:
Xcode 7.1

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