[swift-evolution] [Review] SE-0030 Property Behaviors

Curt Clifton curt at omnigroup.com
Wed Feb 10 21:25:05 CST 2016

Original proposal: https://github.com/apple/swift-evolution/blob/master/proposals/0030-property-behavior-decls.md

# What is your evaluation of the proposal?

I am strongly in favor of the proposal. While I eagerly await some of the work described in future directions—binding the name of the property, in particular—I think the proposal stands tall on its own.

# Is the problem being addressed significant enough to warrant a change to Swift?

Yes. Property behaviors provide a well-founded mechanism to replace several existing special cases in the language. The new mechanism is orthogonal to existing language features, so it actually simplifies the language versus having special cases. As a general tool, it will help developers to eliminate substantial boilerplate in a principled way.

# Does this proposal fit well with the feel and direction of Swift?

Mostly certainly! Like Brent, I've been looking for places in my daily work that could benefit from property behaviors. These come up surprisingly often.

# If you have used other languages or libraries with a similar feature, how do you feel that this proposal compares to those?

I've used both KVC and dynamic method generation in Objective-C for achieving some of the aims satisfied by property behaviors. I expect that property behaviors will prove to be a more approachable and less error prone solution.

# How much effort did you put into your review? A glance, a quick reading, or an in-depth study?

I read all of the preceding discussions and participated in them lightly (2-3 emails sent). I closely read every public draft of the proposal.



Curt Clifton, PhD 
Software Developer 
The Omni Group 

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