FunctionBuildersから見るSwiftUIの文法

SwiftUIの文法の難しいところをFunctionBuildersやその他のSwiftの文法から解説しています。
型がどうなっているのかに着目するとジェネリクスのパワフルさが見えて感動します。

Transcript

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3. struct ContentView: View { var body: some View { VStack(alignment: .leading) { Text("Turtle Rock") .font(.title) HStack { Text("Joshua Tree National Park") .font(.subheadline) Spacer() Text("California") .font(.subheadline) } } .padding() } } &YBNQMF
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5. // Computed Property var hoge : Int { get { return 3 } } // Shorter version var hoge : Int { return 3 } // Shortest version var hoge : Int { 3 } // This above explains this part struct ContentView: View { var body: some View { VStack(alignment: .leading) { .. } } } &YBNQMF
8. (FOFSJDT ɾܕύϥϝʔλʔΛऔΔ͜ͱ͕ग़དྷΔܕ
   ɾ"SSBZܕ΍3FTVMUܕͳͲ
   
9. 74UBDLͷܕύϥϝʔλʔ 74UBDLͷJOJUؔ਺Λ೷͍ͯΈΔͱ
   @ViewBuilder content: () -> Content ͜Ε͸ʜ
10. 7JFX#VJMEFSͱ͸ 'VODUJPO
    #VJMEFSTͱ͍͏࢓૊Έ͕࢖ΘΕ͍ͯΔ
11. 'VODUJPO
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    ɾϦετ΍໦ߏ଄Λѻ͏
    ɾ%4-ΛίϯύΠϥ͕ղੳ
12. 'VODUJPO
    CVJMEFST @_functionBuilder struct Hoge { static func buildBlock(_ a: Int, _ b: Int) -> Int { return a + b } } func fuga(@Hoge a: () -> Int) -> Int { return a() } let puni = fuga { 76 33 } print(puni) // 109
13. 74UBDLͷCVJME#MPDL
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15. HStack { Text("Joshua Tree National Park") Spacer() Text("California") } 4XJGU6*ͷܕΛݟ͍ͯ͘ HStack<TupleView<(Text, Spacer, Text)>> var body: some View { VStack(alignment: .leading) { Text("Turtle Rock") HStack { .. } } } VStack<TupleView<(Text, HStack<TupleView<(Text, Spacer, Text)>>)>>
16. 4XJGU6*ʹ͓͚Δܕ·ͱΊ 7JFXϓϩτίϧʹଋറ͞ΕͨܕύϥϝʔλʔͰ͋Δ $POUFOUΛੜ੒͢ΔͨΊʹ7JFX#VJMEFSTͷ CVJME#MPDLؔ਺͕࢖ΘΕ͍ͯΔ CVJME#MPDLؔ਺͸Ҿ਺͕͍ͭ͘ೖͬͯ͘Δ͔Θ͔Β ͳ͍ͷͰɺͦΕΛ5VQMF7JFXͳͲͱͯ͠ѻͬͯ (FOFSJD
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17. struct ContentView: View { var body: some View { VStack(alignment: .leading) { Text("Turtle Rock") .font(.title) HStack { Text("Joshua Tree National Park") .font(.subheadline) Spacer() Text("California") .font(.subheadline) } } .padding() } } ׬શʹཧղͰ͖Δ
18. ͓͠·͍