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[SR-12178] willSet not firing when used with a property wrapper #54603

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swift-ci opened this issue Feb 11, 2020 · 3 comments
Closed

[SR-12178] willSet not firing when used with a property wrapper #54603

swift-ci opened this issue Feb 11, 2020 · 3 comments
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@theblixguy
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself property wrappers Feature: property wrappers

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@swift-ci
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Previous ID SR-12178
Radar rdar://problem/59496047
Original Reporter camcaine (JIRA User)
Type Bug
Status Resolved
Resolution Done
Environment

Swift 5.2

Xcode Version 11.4 beta (11N111s)

Additional Detail from JIRA
Votes 1
Component/s Compiler
Labels Bug, PropertyWrappers
Assignee @theblixguy
Priority Medium

md5: 7ffc4169185cec192e0c089a29182fa6

relates to:

  • SR-12089 Swift 5.2 snapshot: didSet not called

Issue Description:

willSet observer doesn't fire when used alongside a property wrapper:

@propertyWrapper struct RoundedMeasurement {
    private var measurement: Measurement<UnitMass>

    init(wrappedValue: Measurement<UnitMass>) {
        measurement = wrappedValue.rounded()
    }

    var wrappedValue: Measurement<UnitMass> {
        get { measurement }
        set { measurement = newValue.rounded() }
    }
}

class Weighted {
    @RoundedMeasurement
    var weight = Measurement<UnitMass>(value: 10, unit: .kilograms) {
        willSet {
            print("New Value \(newValue.description)")
        }
    }
}

let weighted = Weighted()

// willSet only fires when the property wrapper is not used.
weighted.weight.convert(to: .pounds)
@theblixguy
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Simpler reproducer that doesn't involve Apple APIs like Measurement, etc:

@propertyWrapper 
struct Foo {
  private var _storage: [Int] = []

  init(wrappedValue value: [Int]) {
    self._storage = value
  }

  var wrappedValue: [Int] {
    get { _storage }
    set { _storage = newValue }
  }
}

class Bar {
  @Foo var someArray = [1, 2, 3] {
    willSet {
      print(newValue) 
    }
  }
}

let bar = Bar()
bar.someArray[0] = 4 // Doesn't call willSet

@beccadax
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@swift-ci create

@slavapestov
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#29931

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
This issue was closed.
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@theblixguy theblixguy

Labels
bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself property wrappers Feature: property wrappers
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@slavapestov @beccadax @theblixguy @swift-ci