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Copy file name to clipboardExpand all lines: CHANGELOG.md
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Swift 5.3
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----------
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*[SR-7083][]:
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Property observers such as `willSet` and `didSet` are now supported on `lazy` properties:
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```swift
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classC {
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lazyvar property: Int=0 {
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willSet { print("willSet called!") } // Okay
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didSet { print("didSet called!") } // Okay
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}
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}
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```
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Note that the initial value of the property will be forced and made available as the `oldValue` for the `didSet` observer, if the property hasn't been accessed yet.
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```swift
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classC {
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lazyvar property: Int=0 {
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didSet { print("Old value: ", oldValue) }
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}
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}
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let c =C()
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c.property=1// Prints 'Old value: 0'
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```
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This could have side-effects, for example if the lazy property's initializer is doing other work.
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*[SE-0268][]:
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A `didSet` observer which does not refer to the `oldValue` in its body or does not explicitly request it by placing it in the parameter list (i.e. `didSet(oldValue)`) will no longer trigger a call to the property getter to fetch the `oldValue`.
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