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打開
Combine
的引擎蓋看看
SWIFT, COMBINE, REACTIVE IPLAYGROUND 2020
游諭
What’s under the hood？
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游諭（@ytyubox）
⾃學程式 iOS - 2018
iT 邦幫忙鐵⼈賽：
30 天了解 Swift 的 Combine
30 天從 Swift 學會 Objective-C
$> whoami
2
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Agenda
Short Introductions
簡單的 Combine 應⽤
combine 的⾓⾊
Behavior test
更進階的 Combine
3
⽬錄
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Agenda
Short Introductions
簡單的 Combine 應⽤
combine 的⾓⾊
Behavior test
更進階的 Combine
4
⽬錄
50 % +
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開始之前
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，這個 Session 將會
介紹如何入⾨ Combine
並不包含解釋 Framework 內部原始碼
開始之前
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Short
Introductions
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SwiftUI
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Combine
SwiftUI
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RxSwift
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https://github.com/ReactiveX
https://github.com/ReactiveCocoa/ReactiveSwift https://developer.apple.com/videos/wwdc2019
Combine
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https://github.com/ReactiveX
https://github.com/ReactiveCocoa/ReactiveSwift https://developer.apple.com/videos/wwdc2019
Functional
Reactive
Programming
Combine
RxSwift
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A unified, declarative API for
processing values over time.
By WWDC 2019: Introducing Combine
Functional
Reactive
Programming
Combine
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A unified, declarative API for
processing values over time.
By WWDC 2019: Introducing Combine
Functional
Reactive
Programming
Combine
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A unified, declarative API for
processing values over time.
Generic
Composition
f
i
rst
Request driven
type safe
By WWDC 2019: Introducing Combine
Combine
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打開 Combine 會發現什麼？
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打開 Combine 發現了⼀隻貓
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Asynchronous
Programming
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來⾃ Apple / Combine
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透過組合處理事件的運算⼦來定制異步事件的應對⽅式。
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來⾃ Apple / Combine
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透過組合處理事件的運算⼦來定制異步事件的應對⽅式。
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來⾃ Apple / Combine
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透過組合處理事件的運算⼦來定制異步事件的應對⽅式。
注意
Apple 這裡的非同步不是指 Dispatch framework
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asynchronous programing
非同步程式設計
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Property Observers ( set / didSet )
Target / Action ( @IBAction )
Notification Center
Ad-hoc Callbacks
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asynchronous programing
非同步程式設計
URLSession.dataTask(with:, completionHandler:)
Key-Value Observing
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Key-Value Observing
複習⼀下
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class KVOTarget: NSObject { @objc dynamic var value = 0 }
let target = KVOTarget()
var captured = [Int?]()
let kvoToken = target.observe(\.value, options: .new) {
(target, change) in
captured.append(change.newValue)
}
XCTAssertEqual(captured, [])
target.value = 1
target.value = 2
XCTAssertEqual(captured, [1, 2])
kvoToken.invalidate()
target.value = 3
XCTAssertEqual(captured, [1, 2])
Key-Value Observing
複習⼀下
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class KVOTarget: NSObject { @objc dynamic var value = 0 }
let target = KVOTarget()
var captured = [Int?]()
let kvoToken = target.observe(\.value, options: .new) {
(target, change) in
captured.append(change.newValue)
}
XCTAssertEqual(captured, [])
target.value = 1
target.value = 2
XCTAssertEqual(captured, [1, 2])
kvoToken.invalidate()
target.value = 3
XCTAssertEqual(captured, [1, 2])
Key-Value Observing
複習⼀下
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class KVOTarget: NSObject { @objc dynamic var value = 0 }
let target = KVOTarget()
var captured = [Int?]()
let kvoToken = target.observe(\.value, options: .new) {
(target, change) in
captured.append(change.newValue)
}
XCTAssertEqual(captured, [])
target.value = 1
target.value = 2
XCTAssertEqual(captured, [1, 2])
kvoToken.invalidate()
target.value = 3
XCTAssertEqual(captured, [1, 2])
Key-Value Observing
複習⼀下
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class KVOTarget: NSObject { @objc dynamic var value = 0 }
let target = KVOTarget()
var captured = [Int?]()
let kvoToken = target.observe(\.value, options: .new) {
(target, change) in
captured.append(change.newValue)
}
XCTAssertEqual(captured, [])
target.value = 1
target.value = 2
XCTAssertEqual(captured, [1, 2])
kvoToken.invalidate()
target.value = 3
XCTAssertEqual(captured, [1, 2])
Key-Value Observing
複習⼀下
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簡單 Combine 應⽤
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import Combine
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URLSession.shared.dataTaskPublisher(for: aURL)
import Combine
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URLSession.shared.dataTaskPublisher(for: aURL)
Publisher
import Combine
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URLSession.shared.dataTaskPublisher(for: aURL)
.map(\.data)
.decode(type: MyModel.self, decoder: JSONDecoder())
Publisher
import Combine
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URLSession.shared.dataTaskPublisher(for: aURL)
.map(\.data)
.decode(type: MyModel.self, decoder: JSONDecoder())
.sink(receiveCompletion: self.receiveCompletionMethod,
receiveValue: self.receiveValueMethod)
AnyCancellable
import Combine
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import Combine
func greet(person: String) throws -> String {
let greeting = "Hello, " + person + "!"
return greeting
}
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func greetPublisher(person: String) -> AnyPublisher {
return Just(person)
.prepend("Hello, ")
.append("!")
.reduce("", +)
.eraseToAnyPublisher()
}
func greet(person: String) throws -> String {
let greeting = "Hello, " + person + "!"
return greeting
}
import Combine
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Combine ⾓⾊
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import Combine
protocol Publisher {
associatedtype Output
associatedtype Failure : Error
func receive(subscriber: S)
where Self.Failure == S.Failure, Self.Output == S.Input
}
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import Combine
protocol Publisher {
...
}
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import Combine
protocol Publisher {
...
}
protocol Subscriber {
associatedtype Input
associatedtype Failure : Error
func receive(subscription: Subscription)
func receive(_ input: Self.Input) -> Subscribers.Demand
func receive(completion: Subscribers.Completion)
}
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import Combine
protocol Publisher {
...
}
protocol Subscriber {
...
}
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protocol Publisher {
...
}
protocol Subscriber {
...
}
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Subscriber
Publisher
import Combine
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Subscriber
Publisher
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Subscriber
Publisher
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Subscriber
Publisher
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Subscriber
Publisher
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Subscriber
Publisher
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Subscriber
Publisher
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Subscriber
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Combine Pattern
From WWDC 2019 - Introducing Combine
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Combine Pattern
From WWDC 2019 - Introducing Combine
來⾃與 Introducing Combine
https://developer.apple.com/videos/play/wwdc2019/722/
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Subscriber
Publisher
subscribe( )
is attached Publisher
Subscriber
Combine Pattern
From WWDC 2019 - Introducing Combine
52
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Subscriber
Publisher
subscribe( )
is attached Publisher
Subscriber
Subscription
receive(subscription: )
sends
Publisher Subscription
Combine Pattern
From WWDC 2019 - Introducing Combine
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Subscriber
Publisher
subscribe( )
is attached Publisher
Subscriber
request(_: Demand)
requests N values
Subscriber
Subscription
receive(subscription: )
sends
Publisher Subscription
Combine Pattern
From WWDC 2019 - Introducing Combine
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Subscriber
Publisher
subscribe( )
is attached Publisher
Subscriber
receive(_: Input)
sends N values or less
Publisher
request(_: Demand)
requests N values
Subscriber
Subscription
receive(subscription: )
sends
Publisher Subscription
Combine Pattern
From WWDC 2019 - Introducing Combine
55
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Subscriber
Publisher
subscribe( )
is attached Publisher
Subscriber
receive(_: Input)
sends N values or less
Publisher
receive(completion:)
sends completion
Publisher
request(_: Demand)
requests N values
Subscriber
Subscription
receive(subscription: )
sends
Publisher Subscription
Combine Pattern
From WWDC 2019 - Introducing Combine
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如果對⼀個 Publisher 重複 Subscribe 呢？
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Publisher Subscriber
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Subscriber No. 2
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Publisher Subscriber
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Subscriber No. 2
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Publisher Subscriber
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Subscriber No. 2
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Publisher Subscriber
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Subscriber No. 2
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Publisher Subscriber
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Subscriber No. 2
Copied Publisher
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Publisher Subscriber
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Subscriber No. 2
Copied Publisher
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Publisher Subscriber
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Subscriber No. 2
Copied Publisher
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Publisher Subscriber
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Subscriber No. 2
Copied Publisher
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Subscriber
Publisher
subscribe( )
receive(_: Input)
sends N values or less
Publisher
receive(completion:)
sends completion
Publisher
request(_: Demand)
Subscription
receive(subscription: )
is attached Publisher
Subscriber
requests N values
Subscriber
sends
Publisher Subscription
Combine Pattern
From WWDC 2019 - Introducing Combine
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receive(subscription: )
Publisher
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Subscriber
subscribe( )
request(_: Demand)
receive(_: Input)
receive(completion:)
Subscription
subscribe( )
receive(_: Input)
sends N values or less
receive(completion:)
sends completion
request(_: Demand)
Subscription
Combine Pattern
From my perspective
Subscription
Subscription
is attached Publisher
Subscriber
requests N values
Subscriber
sends
Publisher Subscription
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Subscription
Publisher
Subscriber
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Combine
Operator
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Publisher
Publisher
Mapper
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Operator
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Operator 其實是 decorator pattern
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Publisher
Operator
class Operator: Publisher {
let concrete: Publisher
}
is a has a
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decorator pattern
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client decor 1 driver
decor 2
action
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decorator pattern
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client decor 1 driver
decor 2
action
addBehavior
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decorator pattern
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client decor 1 driver
decor 2
action
action
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decorator pattern
addBehavior
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client decor 1 driver
decor 2
action
action action
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decorator pattern
addBehavior
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addBehavior
client decor 1 driver
decor 2
action
action action
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decorator pattern
addBehavior
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client decor 1 driver
decor 2
action
action action
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decorator pattern
addBehavior
addBehavior
addBehavior
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Mazinger Z: a Japanese super robot manga series written and illustrated by Go Naga
Has a Man, is a Man.
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無敵鐵⾦剛
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Behavior tests
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AnyCancellable deinit 會⾃動 Cancel
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let subject = PassthroughSubject()
var received = [Event]()
weak var weakCancellable: AnyCancellable?
do {
let anyCancellable = subject
.sink(event: { e in received.append(e) } )
weakCancellable = anyCancellable
subject.send(1)
}
XCTAssertNil(weakCancellable)
subject.send(2)
XCTAssertEqual(received, [1])
AnyCancellable deinit 會⾃動 Cancel
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let subject = PassthroughSubject()
var received = [Event]()
weak var weakCancellable: AnyCancellable?
do {
let anyCancellable = subject
.sink(event: { e in received.append(e) } )
weakCancellable = anyCancellable
subject.send(1)
}
XCTAssertNil(weakCancellable)
subject.send(2)
XCTAssertEqual(received, [1])
AnyCancellable deinit 會⾃動 Cancel
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let subject = PassthroughSubject()
var received = [Event]()
weak var weakCancellable: AnyCancellable?
do {
let anyCancellable = subject
.sink(event: { e in received.append(e) } )
weakCancellable = anyCancellable
subject.send(1)
}
XCTAssertNil(weakCancellable)
subject.send(2)
XCTAssertEqual(received, [1])
AnyCancellable deinit 會⾃動 Cancel
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let subject = PassthroughSubject()
var received = [Event]()
weak var weakCancellable: AnyCancellable?
do {
let anyCancellable = subject
.sink(event: { e in received.append(e) } )
weakCancellable = anyCancellable
subject.send(1)
}
XCTAssertNil(weakCancellable)
subject.send(2)
XCTAssertEqual(received, [1])
AnyCancellable deinit 會⾃動 Cancel
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let subject = PassthroughSubject()
var received = [Event]()
weak var weakCancellable: AnyCancellable?
do {
let anyCancellable = subject
.sink(event: { e in received.append(e) } )
weakCancellable = anyCancellable
subject.send(1)
}
XCTAssertNil(weakCancellable)
subject.send(2)
XCTAssertEqual(received, [1])
AnyCancellable deinit 會⾃動 Cancel
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let subject = PassthroughSubject()
var received = [Event]()
weak var weakCancellable: AnyCancellable?
do {
let anyCancellable = subject
.sink(event: { e in received.append(e) } )
weakCancellable = anyCancellable
subject.send(1)
}
XCTAssertNil(weakCancellable)
subject.send(2)
XCTAssertEqual(received, [1])
AnyCancellable deinit 會⾃動 Cancel
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NSKeyValueObservation deinit 也會⾃動 Cancel
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let target = KVOTarget()
var captured = [Int?]()
weak var weakKvoToken: NSKeyValueObservation?
do {
let token = target.observe(\.value, options: .new) {
(target, change) in
captured.append(change.newValue)
}
weakKvoToken = token
target.value = 1
target.value = 2
XCTAssertEqual(captured, [1, 2])
}
XCTAssertNil(weakKvoToken)
target.value = 3
XCTAssertEqual(captured, [1, 2])
NSKeyValueObservation deinit 也會⾃動 Cancel
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let target = KVOTarget()
var captured = [Int?]()
weak var weakKvoToken: NSKeyValueObservation?
do {
let token = target.observe(\.value, options: .new) {
(target, change) in
captured.append(change.newValue)
}
weakKvoToken = token
target.value = 1
target.value = 2
XCTAssertEqual(captured, [1, 2])
}
XCTAssertNil(weakKvoToken)
target.value = 3
XCTAssertEqual(captured, [1, 2])
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NSKeyValueObservation deinit 也會⾃動 Cancel
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let target = KVOTarget()
var captured = [Int?]()
weak var weakKvoToken: NSKeyValueObservation?
do {
let token = target.observe(\.value, options: .new) {
(target, change) in
captured.append(change.newValue)
}
weakKvoToken = token
target.value = 1
target.value = 2
XCTAssertEqual(captured, [1, 2])
}
XCTAssertNil(weakKvoToken)
target.value = 3
XCTAssertEqual(captured, [1, 2])
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NSKeyValueObservation deinit 也會⾃動 Cancel
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使⽤ Publisher.subscribe 會 Retain Sink
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let subject = PassthroughSubject()
var received = [Event]()
weak var weakSink: Subscribers.Sink?
do {
let sink = Subscribers.Sink{
received.append(.value($0))
}
weakSink = sink
subject.subscribe(sink)
subject.send(1)
}
XCTAssertNotNil(weakSink)
subject.send(2)
weakSink?.cancel()
XCTAssertNil(weakSink)
subject.send(3)
XCTAssertEqual(received, [1, 2])
使⽤ Publisher.subscribe 會 Retain Sink
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let subject = PassthroughSubject()
var received = [Event]()
weak var weakSink: Subscribers.Sink?
do {
let sink = Subscribers.Sink{
received.append(.value($0))
}
weakSink = sink
subject.subscribe(sink)
subject.send(1)
}
XCTAssertNotNil(weakSink)
subject.send(2)
weakSink?.cancel()
XCTAssertNil(weakSink)
subject.send(3)
XCTAssertEqual(received, [1, 2])
使⽤ Publisher.subscribe 會 Retain Sink
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let subject = PassthroughSubject()
var received = [Event]()
weak var weakSink: Subscribers.Sink?
do {
let sink = Subscribers.Sink{
received.append(.value($0))
}
weakSink = sink
subject.subscribe(sink)
subject.send(1)
}
XCTAssertNotNil(weakSink)
subject.send(2)
weakSink?.cancel()
XCTAssertNil(weakSink)
subject.send(3)
XCTAssertEqual(received, [1, 2])
使⽤ Publisher.subscribe 會 Retain Sink
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let subject = PassthroughSubject()
var received = [Event]()
weak var weakSink: Subscribers.Sink?
do {
let sink = Subscribers.Sink{
received.append(.value($0))
}
weakSink = sink
subject.subscribe(sink)
subject.send(1)
}
XCTAssertNotNil(weakSink)
subject.send(2)
weakSink?.cancel()
XCTAssertNil(weakSink)
subject.send(3)
XCTAssertEqual(received, [1, 2])
使⽤ Publisher.subscribe 會 Retain Sink
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let subject = PassthroughSubject()
var received = [Event]()
weak var weakSink: Subscribers.Sink?
do {
let sink = Subscribers.Sink{
received.append(.value($0))
}
weakSink = sink
subject.subscribe(sink)
subject.send(1)
}
XCTAssertNotNil(weakSink)
subject.send(2)
weakSink?.cancel()
XCTAssertNil(weakSink)
subject.send(3)
XCTAssertEqual(received, [1, 2])
使⽤ Publisher.subscribe 會 Retain Sink
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let subject = PassthroughSubject()
var received = [Event]()
weak var weakSink: Subscribers.Sink?
do {
let sink = Subscribers.Sink{
received.append(.value($0))
}
weakSink = sink
subject.subscribe(sink)
subject.send(1)
}
XCTAssertNotNil(weakSink)
subject.send(2)
weakSink?.cancel()
XCTAssertNil(weakSink)
subject.send(3)
XCTAssertEqual(received, [1, 2])
使⽤ Publisher.subscribe 會 Retain Sink
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更進階的 Combine
99
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在開始之前：習慣 Value over time
100
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複習⼀下 ”國中物理“ 直線等加速度運動圖形
101
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複習⼀下 ”國中物理“ 直線等加速度運動圖形
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時間
速
度
時間
位
移
時間
加
速
度
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複習⼀下 ”國中物理“ 直線等加速度運動圖形
103
時間
速
度
時間
位
移
時間
加
速
度
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彈珠圖 marble diagram
事件
Event
截⽌
Completion
❌
Error
事件流
Stream
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彈珠圖 marble diagram
事件流
Stream ❌
Error
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Publisher Subscribe 多次
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Subscriber
Subscriber
Publisher
Publisher Subscribe 多次
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Subscriber
Subscriber
Publisher
Publisher Subscribe 多次
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Subscriber
Subscriber
Publisher
Publisher Subscribe 多次
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Subscriber
Subscriber
Publisher
Publisher Subscribe 多次
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Subscriber
Subscriber
Publisher Subject
Publisher Subscribe 多次
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Subscriber
Subscriber
Publisher
Subject
Publisher Subscribe 多次
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Subscriber
Subscriber
Publisher
Subject
Publisher Subscribe 多次
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Subscriber
Subscriber
Publisher
Subject
Publisher Subscribe 多次
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Subscriber
Subscriber
Publisher Subject
Publisher Subscribe 多次
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Subscriber
Subscriber
Publisher Subject
Publisher Subscribe 多次
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Hot / Cold Publisher
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Cold Publisher
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Subscriber
Publisher
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Cold Publisher
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Subscriber
Publisher
121
Cold Publisher
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Subscriber
Publisher
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Cold Publisher
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Subscriber
Publisher
123
Cold Publisher
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Hot Publisher
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Publisher
125
Hot Publisher
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Publisher
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Hot Publisher
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Subscriber
Publisher
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Hot Publisher
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Subscriber
Publisher
128
Hot Publisher
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Subscriber
Publisher
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Hot Publisher
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Subscriber
Publisher
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Hot Publisher
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Passthrough
Subject
CurrentValue
Subject
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Passthrough
Subject
CurrentValue
Subject
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Passthrough
Subject
CurrentValue
Subject
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Passthrough
Subject
CurrentValue
Subject
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Passthrough
Subject
CurrentValue
Subject
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Passthrough
Subject
CurrentValue
Subject
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let subjectA = PassthroughSubject()
let scanB = subjectA.scan(0, +)
var receivedC = [Event]()
let sinkC = scanB.sink{ e in receivedC.append(e) }
subjectA.send(1...2)
var receivedD = [Event]()
let sinkD = scanB.sink{ e in receivedD.append(e) }
subjectA.send(3...4)
XCTAssertEqual(receivedC, [1, 3, 6, 10])
// 0 + 1...4
XCTAssertEqual(receivedD, [3, 7])
// 0 + 3...4
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let subjectA = PassthroughSubject()
let scanB = subjectA.scan(0, +)
var receivedC = [Event]()
let sinkC = scanB.sink{ e in receivedC.append(e) }
subjectA.send(1...2)
var receivedD = [Event]()
let sinkD = scanB.sink{ e in receivedD.append(e) }
subjectA.send(3...4)
XCTAssertEqual(receivedC, [1, 3, 6, 10])
// 0 + 1...4
XCTAssertEqual(receivedD, [3, 7])
// 0 + 3...4
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let subjectA = PassthroughSubject()
let scanB = subjectA.scan(0, +)
var receivedC = [Event]()
let sinkC = scanB.sink{ e in receivedC.append(e) }
subjectA.send(1...2)
var receivedD = [Event]()
let sinkD = scanB.sink{ e in receivedD.append(e) }
subjectA.send(3...4)
XCTAssertEqual(receivedC, [1, 3, 6, 10])
// 0 + 1...4
XCTAssertEqual(receivedD, [3, 7])
// 0 + 3...4
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FlatMap
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之前複習⼀下 向量投影（內積）
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FlatMap
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FlatMap
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FlatMap
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FlatMap
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FlatMap
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FlatMap
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Error handling By Catch
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Publisher Subscriber
Catch
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Error handling By Catch
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Publisher Subscriber
Catch
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Error handling By Catch
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Publisher Subscriber
Catch
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Error handling By Catch
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Publisher Subscriber
Catch
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Error handling By Catch
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Subscriber
Catch
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Error handling By Catch
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Subscriber
Catch
Recovery
Publisher
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Error handling By Catch
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Subscriber
Catch
Recovery
Publisher
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Error handling By Catch
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Subscriber
Catch
Recovery
Publisher
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Error From TryMap
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Publisher Subscriber
Catch
TryMap
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Error From TryMap
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Publisher Subscriber
Catch
TryMap
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Error From TryMap
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Publisher Subscriber
Catch
TryMap
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Error From TryMap
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Publisher Subscriber
Catch
TryMap
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Error From TryMap
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Publisher Subscriber
Catch
TryMap
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Error From TryMap
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Publisher Subscriber
Catch
TryMap
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Error From TryMap
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Subscriber
Catch
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Error From TryMap
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Subscriber
Catch
Recovery
Publisher
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Error From TryMap
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Subscriber
Catch
Recovery
Publisher
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Error From TryMap
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Subscriber
Catch
Recovery
Publisher
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使⽤ FlatMap 導流
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Publisher Subscriber
FlatMap
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使⽤ FlatMap 導流
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Publisher Subscriber
FlatMap
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使⽤ FlatMap 導流
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Publisher Subscriber
Catch
TryMap
FlatMap
Catch
TryMap
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使⽤ FlatMap 導流
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Publisher Subscriber
Catch
TryMap
FlatMap
Catch
TryMap
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使⽤ FlatMap 導流
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Publisher Subscriber
Catch
TryMap
FlatMap
Catch
TryMap
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使⽤ FlatMap 導流
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Publisher Subscriber
Catch
FlatMap
Catch
Recovery
Publisher
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使⽤ FlatMap 導流
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Publisher Subscriber
FlatMap
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使⽤ FlatMap 導流
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Publisher Subscriber
FlatMap
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使⽤ FlatMap 導流
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Publisher Subscriber
FlatMap
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使⽤ FlatMap 導流
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Publisher Subscriber
FlatMap
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使⽤ FlatMap 導流
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Publisher Subscriber
FlatMap
Catch
TryMap Catch
TryMap
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使⽤ FlatMap 導流
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Publisher Subscriber
FlatMap
Catch
TryMap Catch
TryMap
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使⽤ FlatMap 導流
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Publisher Subscriber
FlatMap
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使⽤ FlatMap 導流
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Publisher Subscriber
FlatMap
✅
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聽完這個 Session
之後呢？
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Apple/Swift Combine Extension
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https://github.com/apple/swift/tree/main/stdlib/public/Darwin/Foundation
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Reactive Programming Taiwan
(RxSwift/Combine)
加入 Telegram 台灣社群
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加入 Combine Community
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watchOS
tvOS
iOS
macOS
Combine
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watchOS
tvOS
iOS
macOS
Linux
WASI
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Apple Combine Documents
WWDC 2019 Session 722, Session 721
cocoawithlove by Matt Gallagher - 22 short tests of Combine
https://www.cocoawithlove.com/blog/twenty-two-short-tests-of-combine-part-1.html
OpenCombine
https://github.com/OpenCombine
ReactiveX.io
http://reactivex.io/
ReactiveCocoa.io
https://reactivecocoa.io/
參考資料
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結論
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Combine 酷嗎？
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Combine 酷嗎？
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Combine 酷嗎？
Combine 好學嗎？
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Combine 酷嗎？
Combine 好學嗎？
✅
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Combine 酷嗎？
Combine 好學嗎？
✅
Combine 好⽤嗎？
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Combine 酷嗎？
Combine 好學嗎？
✅
Combine 好⽤嗎？
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✅
Combine