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DIY your own
Combine framework
Basic Functional Reactive Programming concepts
Li-Heng Hsu 許立衡 @ iPlayground 2019
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– Apple documentation
"The Combine framework provides a declarative
Swift API for processing values over time."
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Concepts
• Builder pattern
• map(_:) method
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Builder pattern
• For constructing instances
• Like initializer, factory method…
1. Create a builder struct
2. Store construction info in it
3. Call its build() method to construct a product
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URLComponents
URL builder
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Combine
Subscription builder
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Builder pattern Combine
Builder Publisher
Construction info Operator
build() Subscriber
Product Subscription
Roles
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CombineDIY.swift
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map(_:) method
• There are different worlds in code
• World of Uncertainty, World of Plurality, World of
Erroneous...
• Instances in these worlds can't be manipulated normally
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Optional
World of Uncertainty
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World of Uncertainty
Cat?
(Cat) -> Double
(Cat?) -> Double?
map(_:)
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Imperative Functional
Metaphor Unwrap values Stack operations
Optional if let x = x { /* ... */ } x.map { x in /* ... */ }
Collection for i in x { /* ... */ } x.forEach { i in /* ... */ }
Result
if case .success(let x) =
result { /* ... */ }
result.map { x in /* ... */ }
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World of Plurality
[Cat]
(Cat) -> Double
([Cat]) -> [Double]
map(_:)
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World of Temporality
Publisher
(Cat) -> Double
(Publisher) ->
Publisher
map(_:)
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DIY
map(_:)
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Feedback
Come find me!
Twitter: @lihenghsu