Properties with initial values
struct S {
let s: String = "hello"
let i: Int = 42
// user declares:
memberwise init() {}
// compiler synthesizes:
init(s: String = "hello", i: Int = 42) {
self.s = s
self.i = i
}
}
I think the sticking issue here is that this synthesis isn't congruent with the
current rules around let:
struct S {
let s: String = "hello"
let i: Int = 42
init(s: String = "hello", i: Int = 42) {
self.s = s
self.i = i
//note: initial value already provided in 'let' declaration
//note: change 'let' to 'var' to make it mutable
}
}
4) var properties with default initializers should have their parameter to the
synthesized initializer defaulted.
I don't think anyone would have issue with this:
struct S {
var s: String = "hello"
var i: Int = 42
// user declares:
memberwise init() {}
// compiler synthesizes:
init(s: String = "hello", i: Int = 42) {
self.s = s
self.i = i
}
}
> On Dec 22, 2015, at 1:02 PM, Matthew Johnson via swift-evolution
> <[email protected]> wrote:
>
>
>> On Dec 22, 2015, at 12:51 PM, Guillaume Lessard via swift-evolution
>> <[email protected] <mailto:[email protected]>> wrote:
>>
>> Hi,
>>
>> Regardless of anything else in the proposal, I strongly dislike its
>> attempted subversion of `let` properties.
>>
>> struct A {
>> let member = 1 // It’s done, over. If that’s not what you want, don’t
>> initialize it here.
>> }
>>
>
> This is not an attempt to subvert `let` properties. The `= 1` in the
> declaration can very reasonably be viewed as a default value that should be
> used if the member is not otherwise initialized.
>
> Why would you have an immutable instance member that is always going to have
> a constant value of 1? That just wastes space by duplicating the constant
> value in many instances. However it is quite reasonable to have an immutable
> instance member that defaults to 1, but may have a different value depending
> on the initializer that is used for the instance.
>
> Matthew
>
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