[Proposal] Struct syntax for requesting a copy with an ivar set to an explicit value

Grant_Sheldon · 2016-07-21T23:08:02.000Z

Hi all,

I am hoping to get some feedback on a new proposal:

gist.github.com

https://gist.github.com/gsheld/542a57c1ca5efe87892a28759215283e

immutable_setter_example.swift

struct Foo {
  var bar = 0
  var baz: String
}

let foo = Foo(bar: 1, baz: "baz")        // Initial struct instance

let fooWithNewBar = foo.withBar(2)       // Returns a new `Foo` with `bar` set to 2; `baz` remains set to "baz".
let fooWithNewBaz = foo.withBaz("BAZ")   // Returns a new `Foo` with `baz` set to "BAZ"; `bar` remains set to 1.

This file has been truncated. show original

The basic idea is to expose syntax that would make it trivial to create a
copy of a Struct instance with an ivar set to a particular value. The
"proposal" I've linked above will give examples and some motivation for the
suggestion. It is a simple gist and not in any way ready for a PR.

Let me know what you think! I'm curious to know if this bit of syntactic
sugar would have value for any of you.

Best wishes,

···

--
Grant Sheldon

Nevin · 2016-07-21T23:16:17.000Z

As an additive proposal this is out of scope for Swift 3. Discussion of
additive proposals resumes August 1.

This functionality has been discussed on-list before, especially regarding
a global “with” function. I believe Erica Sadun has a particularly elegant
implementation.

Nevin

···

On Thu, Jul 21, 2016 at 7:08 PM, Grant Sheldon via swift-evolution < swift-evolution@swift.org> wrote:

Hi all,

I am hoping to get some feedback on a new proposal:

Example: Struct syntax for requesting a copy with an ivar set to an explicit value · GitHub

The basic idea is to expose syntax that would make it trivial to create a
copy of a Struct instance with an ivar set to a particular value. The
"proposal" I've linked above will give examples and some motivation for the
suggestion. It is a simple gist and not in any way ready for a PR.

Let me know what you think! I'm curious to know if this bit of syntactic
sugar would have value for any of you.

Best wishes,

--
Grant Sheldon

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