Adds Publisher.weaklyAssign(to:on:).

[jasdev]

Would love any input on naming here—no strong opinions on .weaklyAssign. 👌🏽

Also, GitHub’s parsing of my commit message. 😂

[codecov]

Codecov Report

Merging #14 into master will increase coverage by 0.05%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #14      +/-   ##
==========================================
+ Coverage   95.77%   95.82%   +0.05%     
==========================================
  Files          28       30       +2     
  Lines        1253     1270      +17     
==========================================
+ Hits         1200     1217      +17     
  Misses         53       53              

Impacted Files	Coverage Δ
Sources/Operators/WeakAssign.swift	100.00% <100.00%> (ø)
Tests/WeakAssignTests.swift	100.00% <100.00%> (ø)

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[freak4pc]

Interesting idea and quite small as well, I'm only trying to think if it's actually useful enough - I'm worried of adding too many "novelty" operators.

I don't want tens of operators called mapWeakly, sinkWeakly, etc. Maybe there's a nice way to generalize it?

[sharplet]

Naming-wise, I'm not sure weaklyAssign, weakAssign, etc. are quite right, because it's the object reference that's weak, not the assignment. Following that logic, if feels like the modifier belongs on the object parameter, so perhaps something like this?

publisher.assign(to: \.foo, onWeak: bar)`

This mirrors capture list syntax somewhat, where it would be spelled [weak bar]. It also perhaps lends itself to this variant for unowned:

publisher.assign(to: \.foo, onUnowned: bar)

I'm sympathetic to @freak4pc's point about generality though. Another option I considered was a function that returns a weak reference, e.g.:

final class WeakBox<Object: AnyObject> {
  weak var object: Object?

  init(_ object: Object) {
    self.object = object
  }
}

func weak<Object: AnyObject>(_ object: Object) -> WeakBox<Object> {
  WeakBox(object)
}

publisher.assign(to: \.foo, on: weak(bar))

I don't love it, but I don't hate it. In Bindings I sidestepped this issue altogether by introducing the BindingOwner protocol, which defines weak capture semantics at the type level, rather than in an ad-hoc fashion through operator overloads.

[jasdev]

@freak4pc, @sharplet: Thank you both for the feedback, means a lot that y’all took the time. 🙏🏽

And totally agree on the ad-hoc’ness of Publisher.weaklyAssign(to:on). I’m guessing the Bindings approach is a bit out of scope for CombineExt—though, Shai can better speak to that 😄. For now, I’ll close this and roll with weak-as-a-function in my projects, since I’m digging how it sort of “promotes” the keyword to a function.

Cheers! 🍻

[jasdev]

(For any future souls stumbling upon this, wrote up some learnings from trying to implement the WeakBox approach, https://jasdev.me/notes/weak-assignment.)