[swift-evolution] Custom didSet methods

[David Sweeris]

What about did/willAdd for all collection types, did/willSetAtIndex for collection types with indexes, and 
did/willSetAtIndexRange for collection types that support subscripting with ranges?

- Dave

> On Jan 12, 2016, at 13:26, Charles Srstka via swift-evolution <swift-evolution at swift.org> wrote:
> 
> Currently, didSet already gets called when a set property is mutated. The only difference I see in this proposal is that it lets you know more precisely what changed, so that you can more efficiently update the UI to reflect the change; i.e. if each item is represented by a view object, and you insert an object, the redraw only needs to occur for the view corresponding to the newly inserted item instead of having to recreate all the views.
> 
> Seems reasonable to me. KVO currently provides this facility in Objective-C.
> 
> Charles
> 
>> On 2016-01-12 07:33, 肇鑫 via swift-evolution wrote:
>> I don't know if this is a good idea. If you insert an item to an
>> array, what should happen? The items after the inserted item should be
>> considered as removed or not? They indexes are changed but the values
>> not.
>> zhaoxin
>> On Tue, Jan 12, 2016 at 7:24 PM, James Campbell via swift-evolution
>> <swift-evolution at swift.org> wrote:
>>> When declaring a collection, it would be nice to have a way of
>>> knowing when an item is set/added and removed.
>>> For example you could trigger a layer to be added to the layer
>>> hiearchy.
>>> var shapeLayers: [CAShapeLayer] {
>>> didAdd(item) {
>>> addSubLayer(item)
>>> }
>>> willRemove(item){
>>> item.removeFromSuperlayer()
>>> }
>>> }
>>> --
>>>  Wizard
>>> james at supmenow.com
>>> +44 7523 279 698 [1]
>>> _______________________________________________
>>> swift-evolution mailing list
>>> swift-evolution at swift.org
>>> https://lists.swift.org/mailman/listinfo/swift-evolution [2]
>> --
>> Owen Zhao
>> Links:
>> ------
>> [1] tel:%2B44%207523%20279%20698
>> [2] https://lists.swift.org/mailman/listinfo/swift-evolution
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