On Mar 6, 2017, at 11:36 PM, Rien via swift-users <swift-users@swift.org> wrote:
> On 07 Mar 2017, at 03:56, Edward Connell via swift-users
> <swift-users@swift.org <mailto:swift-users@swift.org>> wrote:
>
> I would like to have an Array implementation where I get more information
> than just "the whole thing changed".
> As a value type I get it, but lets say it's a list of 500 image info structs
> and it's bound to UI. You change one item, now the whole array changes and
> you have to rebuild the entire visual tree right? Rebuilding the state of
> dependent objects can be really expensive, not just UI things.
In Apple’s Foundation framework, Key-Value Observing (KVO) fills this need, and
can be used with NSMutableArray, including when it’s bridged to Swift. But it
doesn’t really transfer to a pure Swift environment since arrays are value
types: changing one item is actually replacing the entire array with a new one
(optimized through clever internal data-sharing.)
I would assume that the people working on the design of the Swift Foundation
library are thinking about similar observer APIs, but I don’t know the details.
—Jens
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