[swift-users] Should Array's `append(_)` function cause `didSet`?

[Zhao Xin]

Thank you very much Marco. But What is  “outside of an initializer” really
bothers me. **Both** `func bar(keysAndValues:Dictionary<String, String>)`
works now. **Are they really outside ?**

struct Foo {

    var keys = ["z","y","x"]

    {

        didSet {

            keys.sort()

        }

    }



    init(keysAndValues:Dictionary<String, String>) {

        func bar(keysAndValues:Dictionary<String, String>) {

            keys.append(contentsOf: keysAndValues.keys)

        }

        bar(keysAndValues:keysAndValues)

    }



//    private mutating func bar(keysAndValues:Dictionary<String, String>) {

//        keys.append(contentsOf: keysAndValues.keys)

//    }

}


let keysAndValues:Dictionary<String,String> = ["c":"c", "b":"b", "a":"a"]

var foo = Foo(keysAndValues: keysAndValues) // `let foo` is the same result


foo.keys.forEach { print($0) }

/*

 prints

 a

 b

 c

 x

 y

 z

 */


Zhao Xin

On Sat, Jul 8, 2017 at 9:59 AM, Marco S Hyman <marc at snafu.org> wrote:

>
> >     init(keysAndValues:Dictionary<String, String>) {
> >         self.keys.append(contentsOf: keysAndValues.keys)
> >     }
>
> >
> > Above code doesn't call `didSet` in playground. My .swift file is
> similar and didn't call `didSet` either. However, if without a struct,
> `didSet` is called.
>
> “If you don’t need to compute the property but still need to provide code
> that is run before and after setting a new value, use willSet and didSet.
> The code you provide is run any time the value changes outside of an
> initializer.”
>
> Excerpt From: Apple Inc. “The Swift Programming Language (Swift 3.1).”
> iBooks. https://itun.es/us/jEUH0.l
>
> Note “outside of an initializer”.  didSet and willSet are not called in
> initializers.
>
>
>
>
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