Re: [swift-evolution] [Pitch] Allow use associated type outside of its protocol

[曹剑楠 via swift-evolution]

Thanks! Waiting for the new version.

> 在 2017年2月20日，上午7:42，Xiaodi Wu  写道：
> 
> That is a new feature in Swift 3.1.
> 
> 
> On Sun, Feb 19, 2017 at 5:32 PM, 曹剑楠  > wrote:
> Sorry about my typo:
> 
> public struct Album {
> public let sectionedMediaItemInfos: [Sectioned]?}
> 
> 
> public struct Sectioned : SectionProtocol {
> public let title: String?
> public let items: [Item]
> 
> public init() {
> items = []
> title = nil
> }
> }
> 
> public extension Array where Element == Sectioned {
> 
> var itemsCount: Int {
> return reduce(0) { (result, section) in result + section.items.count }
> }
> 
> var items: [Element.Item] {
> return self.flatMap { $0.items }
> }
> }
> 
> Allow extension Array with strict its Element with a struct type (may be 
> generic) is highly wanted feature.
> 
>> 在 2017年2月20日，上午7:28，曹剑楠 > 写道：
>> 
>> 
>> OK, my fault. That solved the problem.
>> 
>>> var items: [Element.SectionItemType]
>> 
>> I should use this.
>> 
>> How about to allow using generic type Section directly instead of declare a 
>> protocol
>> 
>> ```Swift
>> public extension Array where Element == Section {
>> 
>> var itemsCount: Int {
>> return reduce(0) { (result, section) in result + section.items.count 
>> }
>> }
>> 
>> var items: [Element.SectionItemType] {
>> return self.flatMap { $0.items }
>> }
>> }
>> ```
>> 
>>> 在 2017年2月20日，上午7:14，Xiaodi Wu >> > 写道：
>>> 
>>> On Sun, Feb 19, 2017 at 5:04 PM, 曹剑楠 via swift-evolution 
>>> > wrote:
>>> Hi All,
>>> 
>>> I’m coding for section like data structure. 
>>> For example:
>>> 
>>> I have an Album struct, which has many MediaItems.
>>> It has a sectioned property called "sectionedMediaItemInfos", which is an 
>>> array of sections.
>>> Each section represents for a disc, and has an "items" array contains all 
>>> MedaItems in that disc.
>>> 
>>> The define code is like:
>>> 
>>> ```Swift
>>> public struct Album {
>>> public let sectionedMediaItemInfos: [Sectioned]?
>>> }
>>> 
>>> public struct Sectioned : SectionProtocol {
>>> public let title: String?
>>> public let items: [Item]
>>> 
>>> public init() {
>>> items = []
>>> title = nil
>>> }
>>> }
>>> 
>>> public protocol SectionProtocol {
>>> associatedtype SectionItemType
>>> var items: [SectionItemType] { get }
>>> }
>>> ```
>>> 
>>> Now I want to define some extra properties for sections array, like
>>> "sectionMediaItemInfos"."itemsCount" that count all items in each sections.
>>> So I can write that extension:
>>> 
>>> ```Swift
>>> public extension Array where Element : SectionProtocol {
>>> 
>>> var itemsCount: Int {
>>> return reduce(0) { (result, section) in result + 
>>> section.items.count }
>>> }
>>> 
>>> }
>>> ```
>>> 
>>> So I can get my itemsCount with code like:
>>> 
>>> ```Swift
>>> album.sectionedMediaItemInfos.itemsCount
>>> ```
>>> 
>>> That looks good.
>>> 
>>> Then I want to define code to return all items in this sectioned property.
>>> 
>>> 
>>> ```Swift
>>> public extension Array where Element : SectionProtocol {
>>> var items: [SectionProtocol.SectionItemType] {
>>> return .flatMap { $0.items }
>>> }
>>> }
>>> ```
>>>  
>>> Sorry, I'm reading this quickly, but I'm confused as to why you're not 
>>> writing `var items: [Element.SectionItemType]`. That seems to be what you 
>>> want, no? `SectionProtocol.SectionItemType` has no constraints and, even if 
>>> the grammar allowed you to write it, would have to be equivalent to `Any`.
>>> 
>>> This doesn’t work. It reported as "Cannot use associated type 
>>> 'SectionItemType' outside of its protocol"
>>> 
>>> The only way to achieve my goals is to untyped the extended "items" 
>>> property:
>>> 
>>> ```Swift
>>> public extension Array where Element : SectionProtocol {
>>> var items: [Any] {
>>> return self.flatMap { $0.items }
>>> }
>>> }
>>> ```
>>> 
>>> Which is not perfect for this case.
>>> 
>>> 
>>> So in this special case, I think allow use associated type outside of its 
>>> protocol is necessary.
>>> 
>>> And we may allow define protocol with generic type. That would be more 
>>> convenient.
>>> 
>>> 
>>> ```Swift
>>> public struct Album {
>>> public let sectionedMediaItemInfos: [Sectioned]?
>>> }
>>> 
>>> 
>>> public struct Sectioned : SectionProtocol {
>>> public let title: String?
>>> public let items: [Item]
>>> 
>>> public init() {
>>> items = []
>>> title = nil
>>> }
>>> }
>>> 
>>> public protocol SectionProtocol {
>>> var items: [SectionItemType] { get }
>>> }
>>> 
>>> 
>>> public extension Array where Element : SectionProtocol {
>>> var items: 

Re: [swift-evolution] [Pitch] Allow use associated type outside of its protocol

[Xiaodi Wu via swift-evolution]

That is a new feature in Swift 3.1.


On Sun, Feb 19, 2017 at 5:32 PM, 曹剑楠  wrote:

> Sorry about my typo:
>
> public struct Album {
>> public let sectionedMediaItemInfos: [Sectioned]?}
>>
>>
>> public struct Sectioned : SectionProtocol {
>> public let title: String?
>> public let items: [Item]
>>
>> public init() {
>> items = []
>> title = nil
>> }
>> }
>>
>
> public extension Array where Element == Sectioned {
>
>
> var itemsCount: Int {
> return reduce(0) { (result, section) in result +
> section.items.count }
> }
>
>
> var items: [Element.Item] {
> return self.flatMap { $0.items }
> }
> }
>
> Allow extension Array with strict its Element with a struct type (may be
> generic) is highly wanted feature.
>
> 在 2017年2月20日，上午7:28，曹剑楠  写道：
>
>
> OK, my fault. That solved the problem.
>
> var items: [Element.SectionItemType]
>>
>
> I should use this.
>
> How about to allow using generic type Section directly instead of declare
> a protocol
>
> ```Swift
> public extension Array where Element == Section {
>
> var itemsCount: Int {
> return reduce(0) { (result, section) in result +
> section.items.count }
> }
>
> var items: [Element.SectionItemType] {
> return self.flatMap { $0.items }
> }
> }
> ```
>
> 在 2017年2月20日，上午7:14，Xiaodi Wu  写道：
>
> On Sun, Feb 19, 2017 at 5:04 PM, 曹剑楠 via swift-evolution <
> swift-evolution@swift.org> wrote:
>
>> Hi All,
>>
>> I’m coding for section like data structure.
>> For example:
>>
>> I have an Album struct, which has many MediaItems.
>> It has a sectioned property called "sectionedMediaItemInfos", which is an
>> array of sections.
>> Each section represents for a disc, and has an "items" array contains
>> all MedaItems in that disc.
>>
>> The define code is like:
>>
>> ```Swift
>> public struct Album {
>> public let sectionedMediaItemInfos: [Sectioned]?
>> }
>>
>> public struct Sectioned : SectionProtocol {
>> public let title: String?
>> public let items: [Item]
>>
>> public init() {
>> items = []
>> title = nil
>> }
>> }
>>
>> public protocol SectionProtocol {
>> associatedtype SectionItemType
>> var items: [SectionItemType] { get }
>> }
>> ```
>>
>> Now I want to define some extra properties for sections array, like
>> "sectionMediaItemInfos"."itemsCount" that count all items in each
>> sections.
>> So I can write that extension:
>>
>> ```Swift
>> public extension Array where Element : SectionProtocol {
>>
>> var itemsCount: Int {
>> return reduce(0) { (result, section) in result + section.items.
>> count }
>> }
>>
>> }
>> ```
>>
>> So I can get my itemsCount with code like:
>>
>> ```Swift
>> album.sectionedMediaItemInfos.itemsCount
>> ```
>>
>> That looks good.
>>
>> Then I want to define code to return all items in this sectioned property.
>>
>>
>> ```Swift
>> public extension Array where Element : SectionProtocol {
>> var items: [SectionProtocol.SectionItemType] {
>> return .flatMap { $0.items }
>> }
>> }
>> ```
>>
>
> Sorry, I'm reading this quickly, but I'm confused as to why you're not
> writing `var items: [Element.SectionItemType]`. That seems to be what you
> want, no? `SectionProtocol.SectionItemType` has no constraints and, even
> if the grammar allowed you to write it, would have to be equivalent to
> `Any`.
>
> This doesn’t work. It reported as "Cannot use associated type
>> 'SectionItemType' outside of its protocol"
>>
>> The only way to achieve my goals is to untyped the extended "items"
>> property:
>>
>> ```Swift
>> public extension Array where Element : SectionProtocol {
>> var items: [Any] {
>> return self.flatMap { $0.items }
>> }
>> }
>> ```
>>
>> Which is not perfect for this case.
>>
>>
>> So in this special case, I think allow use associated type outside of its
>> protocol is necessary.
>>
>> And we may allow define protocol with generic type. That would be more
>> convenient.
>>
>>
>> ```Swift
>> public struct Album {
>> public let sectionedMediaItemInfos: [Sectioned]?
>> }
>>
>>
>> public struct Sectioned : SectionProtocol {
>> public let title: String?
>> public let items: [Item]
>>
>> public init() {
>> items = []
>> title = nil
>> }
>> }
>>
>> public protocol SectionProtocol {
>> var items: [SectionItemType] { get }
>> }
>>
>>
>> public extension Array where Element : SectionProtocol {
>> var items: [Element.SectionItemType] {
>> return self.flatMap { $0.items }
>> }
>> }
>>
>> ```
>>
>> Thank all!
>>
>> Jiannan
>>
>>
>>
>>
>> ___
>> swift-evolution mailing list
>> swift-evolution@swift.org
>> https://lists.swift.org/mailman/listinfo/swift-evolution
>>
>>
>
>
>
___
swift-evolution mailing list
swift-evolution@swift.org

Re: [swift-evolution] [Pitch] Allow use associated type outside of its protocol

[曹剑楠 via swift-evolution]

Sorry about my typo:

public struct Album {
public let sectionedMediaItemInfos: [Sectioned]?}


public struct Sectioned : SectionProtocol {
public let title: String?
public let items: [Item]

public init() {
items = []
title = nil
}
}

public extension Array where Element == Sectioned {

var itemsCount: Int {
return reduce(0) { (result, section) in result + section.items.count }
}

var items: [Element.Item] {
return self.flatMap { $0.items }
}
}

Allow extension Array with strict its Element with a struct type (may be 
generic) is highly wanted feature.

> 在 2017年2月20日，上午7:28，曹剑楠  写道：
> 
> 
> OK, my fault. That solved the problem.
> 
>> var items: [Element.SectionItemType]
> 
> I should use this.
> 
> How about to allow using generic type Section directly instead of declare a 
> protocol
> 
> ```Swift
> public extension Array where Element == Section {
> 
> var itemsCount: Int {
> return reduce(0) { (result, section) in result + section.items.count }
> }
> 
> var items: [Element.SectionItemType] {
> return self.flatMap { $0.items }
> }
> }
> ```
> 
>> 在 2017年2月20日，上午7:14，Xiaodi Wu > > 写道：
>> 
>> On Sun, Feb 19, 2017 at 5:04 PM, 曹剑楠 via swift-evolution 
>> > wrote:
>> Hi All,
>> 
>> I’m coding for section like data structure. 
>> For example:
>> 
>> I have an Album struct, which has many MediaItems.
>> It has a sectioned property called "sectionedMediaItemInfos", which is an 
>> array of sections.
>> Each section represents for a disc, and has an "items" array contains all 
>> MedaItems in that disc.
>> 
>> The define code is like:
>> 
>> ```Swift
>> public struct Album {
>> public let sectionedMediaItemInfos: [Sectioned]?
>> }
>> 
>> public struct Sectioned : SectionProtocol {
>> public let title: String?
>> public let items: [Item]
>> 
>> public init() {
>> items = []
>> title = nil
>> }
>> }
>> 
>> public protocol SectionProtocol {
>> associatedtype SectionItemType
>> var items: [SectionItemType] { get }
>> }
>> ```
>> 
>> Now I want to define some extra properties for sections array, like
>> "sectionMediaItemInfos"."itemsCount" that count all items in each sections.
>> So I can write that extension:
>> 
>> ```Swift
>> public extension Array where Element : SectionProtocol {
>> 
>> var itemsCount: Int {
>> return reduce(0) { (result, section) in result + section.items.count 
>> }
>> }
>> 
>> }
>> ```
>> 
>> So I can get my itemsCount with code like:
>> 
>> ```Swift
>> album.sectionedMediaItemInfos.itemsCount
>> ```
>> 
>> That looks good.
>> 
>> Then I want to define code to return all items in this sectioned property.
>> 
>> 
>> ```Swift
>> public extension Array where Element : SectionProtocol {
>> var items: [SectionProtocol.SectionItemType] {
>> return .flatMap { $0.items }
>> }
>> }
>> ```
>>  
>> Sorry, I'm reading this quickly, but I'm confused as to why you're not 
>> writing `var items: [Element.SectionItemType]`. That seems to be what you 
>> want, no? `SectionProtocol.SectionItemType` has no constraints and, even if 
>> the grammar allowed you to write it, would have to be equivalent to `Any`.
>> 
>> This doesn’t work. It reported as "Cannot use associated type 
>> 'SectionItemType' outside of its protocol"
>> 
>> The only way to achieve my goals is to untyped the extended "items" property:
>> 
>> ```Swift
>> public extension Array where Element : SectionProtocol {
>> var items: [Any] {
>> return self.flatMap { $0.items }
>> }
>> }
>> ```
>> 
>> Which is not perfect for this case.
>> 
>> 
>> So in this special case, I think allow use associated type outside of its 
>> protocol is necessary.
>> 
>> And we may allow define protocol with generic type. That would be more 
>> convenient.
>> 
>> 
>> ```Swift
>> public struct Album {
>> public let sectionedMediaItemInfos: [Sectioned]?
>> }
>> 
>> 
>> public struct Sectioned : SectionProtocol {
>> public let title: String?
>> public let items: [Item]
>> 
>> public init() {
>> items = []
>> title = nil
>> }
>> }
>> 
>> public protocol SectionProtocol {
>> var items: [SectionItemType] { get }
>> }
>> 
>> 
>> public extension Array where Element : SectionProtocol {
>> var items: [Element.SectionItemType] {
>> return self.flatMap { $0.items }
>> }
>> }
>> 
>> ```
>> 
>> Thank all!
>> 
>> Jiannan
>> 
>> 
>> 
>> 
>> ___
>> swift-evolution mailing list
>> swift-evolution@swift.org 
>> https://lists.swift.org/mailman/listinfo/swift-evolution 
>> 
>> 
>> 
> 

___
swift-evolution 

Re: [swift-evolution] [Pitch] Allow use associated type outside of its protocol

[曹剑楠 via swift-evolution]

OK, my fault. That solved the problem.

> var items: [Element.SectionItemType]

I should use this.

How about to allow using generic type Section directly instead of declare a 
protocol

```Swift
public extension Array where Element == Section {

var itemsCount: Int {
return reduce(0) { (result, section) in result + section.items.count }
}

var items: [Element.SectionItemType] {
return self.flatMap { $0.items }
}
}
```

> 在 2017年2月20日，上午7:14，Xiaodi Wu  写道：
> 
> On Sun, Feb 19, 2017 at 5:04 PM, 曹剑楠 via swift-evolution 
> > wrote:
> Hi All,
> 
> I’m coding for section like data structure. 
> For example:
> 
> I have an Album struct, which has many MediaItems.
> It has a sectioned property called "sectionedMediaItemInfos", which is an 
> array of sections.
> Each section represents for a disc, and has an "items" array contains all 
> MedaItems in that disc.
> 
> The define code is like:
> 
> ```Swift
> public struct Album {
> public let sectionedMediaItemInfos: [Sectioned]?
> }
> 
> public struct Sectioned : SectionProtocol {
> public let title: String?
> public let items: [Item]
> 
> public init() {
> items = []
> title = nil
> }
> }
> 
> public protocol SectionProtocol {
> associatedtype SectionItemType
> var items: [SectionItemType] { get }
> }
> ```
> 
> Now I want to define some extra properties for sections array, like
> "sectionMediaItemInfos"."itemsCount" that count all items in each sections.
> So I can write that extension:
> 
> ```Swift
> public extension Array where Element : SectionProtocol {
> 
> var itemsCount: Int {
> return reduce(0) { (result, section) in result + section.items.count }
> }
> 
> }
> ```
> 
> So I can get my itemsCount with code like:
> 
> ```Swift
> album.sectionedMediaItemInfos.itemsCount
> ```
> 
> That looks good.
> 
> Then I want to define code to return all items in this sectioned property.
> 
> 
> ```Swift
> public extension Array where Element : SectionProtocol {
> var items: [SectionProtocol.SectionItemType] {
> return .flatMap { $0.items }
> }
> }
> ```
>  
> Sorry, I'm reading this quickly, but I'm confused as to why you're not 
> writing `var items: [Element.SectionItemType]`. That seems to be what you 
> want, no? `SectionProtocol.SectionItemType` has no constraints and, even if 
> the grammar allowed you to write it, would have to be equivalent to `Any`.
> 
> This doesn’t work. It reported as "Cannot use associated type 
> 'SectionItemType' outside of its protocol"
> 
> The only way to achieve my goals is to untyped the extended "items" property:
> 
> ```Swift
> public extension Array where Element : SectionProtocol {
> var items: [Any] {
> return self.flatMap { $0.items }
> }
> }
> ```
> 
> Which is not perfect for this case.
> 
> 
> So in this special case, I think allow use associated type outside of its 
> protocol is necessary.
> 
> And we may allow define protocol with generic type. That would be more 
> convenient.
> 
> 
> ```Swift
> public struct Album {
> public let sectionedMediaItemInfos: [Sectioned]?
> }
> 
> 
> public struct Sectioned : SectionProtocol {
> public let title: String?
> public let items: [Item]
> 
> public init() {
> items = []
> title = nil
> }
> }
> 
> public protocol SectionProtocol {
> var items: [SectionItemType] { get }
> }
> 
> 
> public extension Array where Element : SectionProtocol {
> var items: [Element.SectionItemType] {
> return self.flatMap { $0.items }
> }
> }
> 
> ```
> 
> Thank all!
> 
> Jiannan
> 
> 
> 
> 
> ___
> swift-evolution mailing list
> swift-evolution@swift.org 
> https://lists.swift.org/mailman/listinfo/swift-evolution 
> 
> 
> 

___
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https://lists.swift.org/mailman/listinfo/swift-evolution

Re: [swift-evolution] [Pitch] Allow use associated type outside of its protocol

[Xiaodi Wu via swift-evolution]

On Sun, Feb 19, 2017 at 5:04 PM, 曹剑楠 via swift-evolution <
swift-evolution@swift.org> wrote:

> Hi All,
>
> I’m coding for section like data structure.
> For example:
>
> I have an Album struct, which has many MediaItems.
> It has a sectioned property called "sectionedMediaItemInfos", which is an
> array of sections.
> Each section represents for a disc, and has an "items" array contains all
> MedaItems in that disc.
>
> The define code is like:
>
> ```Swift
> public struct Album {
> public let sectionedMediaItemInfos: [Sectioned]?
> }
>
> public struct Sectioned : SectionProtocol {
> public let title: String?
> public let items: [Item]
>
>
> public init() {
> items = []
> title = nil
> }
> }
>
> public protocol SectionProtocol {
> associatedtype SectionItemType
> var items: [SectionItemType] { get }
> }
> ```
>
> Now I want to define some extra properties for sections array, like
> "sectionMediaItemInfos"."itemsCount" that count all items in each
> sections.
> So I can write that extension:
>
> ```Swift
> public extension Array where Element : SectionProtocol {
>
>
> var itemsCount: Int {
> return reduce(0) { (result, section) in result + section.items.
> count }
> }
>
> }
> ```
>
> So I can get my itemsCount with code like:
>
> ```Swift
> album.sectionedMediaItemInfos.itemsCount
> ```
>
> That looks good.
>
> Then I want to define code to return all items in this sectioned property.
>
>
> ```Swift
> public extension Array where Element : SectionProtocol {
> var items: [SectionProtocol.SectionItemType] {
> return .flatMap { $0.items }
> }
> }
> ```
>

Sorry, I'm reading this quickly, but I'm confused as to why you're not
writing `var items: [Element.SectionItemType]`. That seems to be what you
want, no? `SectionProtocol.SectionItemType` has no constraints and, even if
the grammar allowed you to write it, would have to be equivalent to `Any`.

This doesn’t work. It reported as "Cannot use associated type
> 'SectionItemType' outside of its protocol"
>
> The only way to achieve my goals is to untyped the extended "items"
> property:
>
> ```Swift
> public extension Array where Element : SectionProtocol {
> var items: [Any] {
> return self.flatMap { $0.items }
> }
> }
> ```
>
> Which is not perfect for this case.
>
>
> So in this special case, I think allow use associated type outside of its
> protocol is necessary.
>
> And we may allow define protocol with generic type. That would be more
> convenient.
>
>
> ```Swift
> public struct Album {
> public let sectionedMediaItemInfos: [Sectioned]?
> }
>
>
> public struct Sectioned : SectionProtocol {
> public let title: String?
> public let items: [Item]
>
> public init() {
> items = []
> title = nil
> }
> }
>
> public protocol SectionProtocol {
> var items: [SectionItemType] { get }
> }
>
>
> public extension Array where Element : SectionProtocol {
> var items: [Element.SectionItemType] {
> return self.flatMap { $0.items }
> }
> }
>
> ```
>
> Thank all!
>
> Jiannan
>
>
>
>
> ___
> swift-evolution mailing list
> swift-evolution@swift.org
> https://lists.swift.org/mailman/listinfo/swift-evolution
>
>
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