[Review] SE-0024 "Optional Value Setter `??=`"

(John Lin) #1

What is your evaluation of the proposal?

-1 for this. Although the proposal was initially intended for property usage, I think the most wide spread usage will be on local variables. And this will encourage use usage of var instead of let.
For example:

var foo = optionalOutput()
foo??= bar


let foo = optionalOutput() ?? bar

The proposed ??= may create many unnecessary var usage just because they want to use the ??= shorthand.

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

No, It can be implemented as a extension if needed.
We already got default value for property, default parameter value for functions, and ?? for local variable usage.

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

No. It’ll encourage unnecessary usage of var.

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

The ||= operator in ruby. But the reason why ||= is popular is that ruby has no support for keyword argument before ruby 2.0. For example:
def foo(options={})
using ||= is the de factor way to set value to options[:bar]

but after ruby 2.0 following method is preferred

def foo(bar: “default”)
which eliminates the need of ||= operator

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

Read though the origin thread, read the proposal, read some of the reviews.