SwiftUIでの非同期処理データの状態管理を考える

!LOUL%BZ ʙ5SBDL$ 4XJGU6*Ͱͷඇಉظॲཧσʔλͷ ঢ়ଶ؅ཧΛߟ͑Δ J04%$JPTEDD

ʮඇಉظॲཧσʔλͷঢ়ଶ؅ཧʯͱ͸

ʮඇಉظॲཧσʔλͷঢ়ଶ؅ཧʯͱ͸ ੒ޭ ࣦഊ ϩʔυத

ʮඇಉظॲཧσʔλͷঢ়ଶ؅ཧʯͱ͸ w ඇಉظʹσʔλΛදࣔ͢Δࡍͷը໘ͷঢ়ଶ؅ཧ w ঢ়ଶ w ϩʔυத w ੒ޭ w
ࣦഊ

ʮඇಉظॲཧσʔλͷঢ়ଶ؅ཧʯͱ͸ ੒ޭ ϩʔυத

ʮඇಉظॲཧσʔλͷঢ়ଶ؅ཧʯͱ͸ ੒ޭ ϩʔυத ੒ޭ ࣦഊ

࿩͢͜ͱ w ඇಉظॲཧσʔλͷঢ়ଶ؅ཧํ๏Λ༷ʑͳ࢓༷Λݩʹ࣮૷ɾߟ࡯

࿩͢͜ͱ w ඇಉظॲཧσʔλͷঢ়ଶ؅ཧํ๏Λ༷ʑͳ࢓༷Λݩʹ࣮૷ɾߟ࡯ w ख๏ w FOVNΛ༻͍ͨख๏ w ίϯϙʔωϯτΛ༻͍ͨख๏

࿩͢͜ͱ w ඇಉظॲཧσʔλͷঢ়ଶ؅ཧํ๏Λ༷ʑͳ࢓༷Λݩʹ࣮૷ɾߟ࡯ w ख๏ w FOVNΛ༻͍ͨख๏ w ίϯϙʔωϯτΛ༻͍ͨख๏ w
ओޠ͕େ͖͍ςʔϚͳͷͰɺߟ͑ํͷҰͭͱͯ͠ଊ͑ͭͭ   վળ఺΍৽ͨͳࢹ఺͕͋Ε͹࣭໰ɾίϝϯτ௖͚ͨΒخ͍͠Ͱ͢👍

$BTF FOVNͷಋೖ

$BTFFOVNͷಋೖ

#FGPSF

$BTFFOVNͷಋೖ#FGPSF ঢ়ଶͷએݴ @State private var data: User? @State private var
error: (any Error)? @State private var isLoading = false

$BTFFOVNͷಋೖ#FGPSF 7JFXͷग़͠Θ͚ var body: some View { List { if
isLoading { EmptyView() } else { if let data { content(user: data) } else if error != nil { ErrorStateView() } } } .overlay { if isLoading { ProgressView() } } }

$BTFFOVNͷಋೖ#FGPSF var body: some View { List { if isLoading
{ EmptyView() } else { if let data { content(user: data) } else if error != nil { ErrorStateView() } } } .overlay { if isLoading { ProgressView() } } } ϩʔυத 7JFXͷग़͠Θ͚

{ EmptyView() } else { if let data { content(user: data) } else if error != nil { ErrorStateView() } } } .overlay { if isLoading { ProgressView() } } } ϩʔυத ੒ޭ 7JFXͷग़͠Θ͚

{ EmptyView() } else { if let data { content(user: data) } else if error != nil { ErrorStateView() } } } .overlay { if isLoading { ProgressView() } } } ϩʔυத ੒ޭ ࣦഊ 7JFXͷग़͠Θ͚

$BTFFOVNͷಋೖ#FGPSF ঢ়ଶͷૢ࡞ʢඇಉظॲཧʣ func fetchUser() async { if isLoading { return
} isLoading = true data = nil error = nil do { data = try await API.getUser() } catch { self.error = error } isLoading = false }

} isLoading = true data = nil error = nil do { data = try await API.getUser() } catch { self.error = error } isLoading = false } ϩʔυ։࢝

} isLoading = true data = nil error = nil do { data = try await API.getUser() } catch { self.error = error } isLoading = false } "1*Λୟ͘ ϩʔυ։࢝

} isLoading = true data = nil error = nil do { data = try await API.getUser() } catch { self.error = error } isLoading = false } "1*Λୟ͘ ࣦഊͳΒFSSPS ϩʔυ։࢝

} isLoading = true data = nil error = nil do { data = try await API.getUser() } catch { self.error = error } isLoading = false } "1*Λୟ͘ ࣦഊͳΒFSSPS ϩʔυऴྃ ϩʔυ։࢝

$BTFFOVNͷಋೖ#FGPSF ·ͱΊ w ঢ়ଶͷએݴม਺ w 7JFXͷग़͠Θ͚ม਺Λར༻͠෼ذ w ঢ়ଶૢ࡞ม਺Λผʑʹૢ࡞

$BTFFOVNͷಋೖ#FGPSF ໰୊఺JGͷωετ var body: some View { List { if
isLoading { EmptyView() } else { if let data { content(user: data) } else if error != nil { ErrorStateView() } } } .overlay { if isLoading { ProgressView() } } } ωετ͕ਂ͍

$BTFFOVNͷಋೖ#FGPSF ໰୊఺ม਺Λผʑʹૢ࡞͢Δͷ͕൥ࡶ func fetchUser() async { if isLoading { return
} isLoading = true data = nil error = nil do { data = try await API.getUser() } catch { self.error = error } isLoading = false } લճͷঢ়ଶΛ࡟আ

$BTFFOVNͷಋೖ#FGPSF ໰୊఺ม਺Λผʑʹૢ࡞͢Δͷ͕൥ࡶ func fetchUser() async { if isLoading { return
} isLoading = true data = nil error = nil do { data = try await API.getUser() } catch { self.error = error } isLoading = false } ݁Ռͷ୅ೖͱ ϩʔυऴ͕ྃಠཱ લճͷঢ়ଶΛ࡟আ

$BTFFOVNͷಋೖ#FGPSF ໰୊఺ w ঢ়ଶͷએݴม਺ w 7JFXͷग़͠Θ͚ม਺Λར༻͠෼ذ w ωετ͕ਂ͍ w ঢ়ଶૢ࡞ม਺Λผʑʹૢ࡞
w ผʑͷૢ࡞͕൥ࡶ

$BTFFOVNͷಋೖ"GUFS ঢ়ଶͷએݴ enum DataState<V, E: Error> { case idle case
loading case success(V) case failure(E) } @State private var dataState: DataState<User, any Error> = .idle

$BTFFOVNͷಋೖ"GUFS ঢ়ଶͷએݴ enum DataState<V, E: Error> { case idle case
loading case success(V) case failure(E) } @State private var dataState: DataState<User, any Error> = .idle ม਺͕ͭ

$BTFFOVNͷಋೖ"GUFS 7JFXͷग़͠Θ͚ var body: some View { List { switch
dataState { case .idle, .loading: EmptyView() case .success(let value): content(user: value) case .failure: ErrorStateView() } } .overlay { if dataState.isLoading { ProgressView() } } }

dataState { case .idle, .loading: EmptyView() case .success(let value): content(user: value) case .failure: ErrorStateView() } } .overlay { if dataState.isLoading { ProgressView() } } } ωετ͕ͭ

dataState { case .idle, .loading: EmptyView() case .success(let value): content(user: value) case .failure: ErrorStateView() } } .overlay { if dataState.isLoading { ProgressView() } } } extension DataState { var isLoading: Bool { if case .loading = self { return true } return false } }

$BTFFOVNͷಋೖ"GUFS ঢ়ଶͷૢ࡞ʢඇಉظॲཧʣ func fetchUser() async { if dataState.isLoading { return
} dataState = .loading do { dataState = .success(try await API.getUser()) } catch { dataState = .failure(error) } }

$BTFFOVNͷಋೖ"GUFS ঢ়ଶͷૢ࡞ʢඇಉظॲཧʣ func fetchUser() async { if dataState.isLoading { return
} dataState = .loading do { dataState = .success(try await API.getUser()) } catch { dataState = .failure(error) } } લճͷঢ়ଶ΋࡟আ JT-PBEJOHGBMTF ΋ෆཁ

$BTFFOVNͷಋೖ"GUFS FOVNΛ༻͍ͨঢ়ଶ؅ཧ w ঢ়ଶͷએݴม਺ w 7JFXͷग़͠Θ͚ม਺ͷTXJUDI w ঢ়ଶૢ࡞ม਺ͷૢ࡞

$BTFFOVNͷಋೖ"GUFS FOVNΛ༻͍ͨঢ়ଶ؅ཧ w ঢ়ଶͷએݴม਺ w 7JFXͷग़͠Θ͚ม਺ͷTXJUDI w ঢ়ଶૢ࡞ม਺ͷૢ࡞ w FOVNʹΑͬͯը໘ͷঢ়ଶ͕໌֬ʹͳΓՄಡੑ΋޲্

$BTF ࠶ಡΈࠐΈத΋σʔλΛදࣔ

$BTF࠶ಡΈࠐΈத΋σʔλΛදࣔ ཧ૝ͷڍಈ

$BTF࠶ಡΈࠐΈத΋σʔλΛදࣔ ཧ૝ͷڍಈ ϩʔυͱσʔλ͕ ಉ࣌ʹදࣔ

#FGPSF

$BTF࠶ಡΈࠐΈத΋σʔλΛදࣔ#FGPSF $BTFͷFOVNͰ࣮૷ enum DataState<V, E: Error> { case idle case
loading case success(V) case failure(E) } @State private var dataState: DataState<User, any Error> = .idle

var body: some View { List { switch dataState {
case .idle, .loading: EmptyView() case .success(let value): content(user: value) case .failure: ErrorStateView() } } .overlay { if dataState.isLoading { ProgressView() } } } $BTF࠶ಡΈࠐΈத΋σʔλΛදࣔ#FGPSF $BTFͷFOVNͰ࣮૷

case .idle, .loading: EmptyView() case .success(let value): content(user: value) case .failure: ErrorStateView() } } .overlay { if dataState.isLoading { ProgressView() } } } $BTF࠶ಡΈࠐΈத΋σʔλΛදࣔ#FGPSF $BTFͷFOVNͰ࣮૷ ɾϩʔυதͩͱσʔλ͕ফ͑Δ ɾϓϧϦϑͱೋॏʹϩʔυ͕දࣔ

case .idle, .loading: EmptyView() case .success(let value): content(user: value) case .failure: ErrorStateView() } } .overlay { if dataState.isLoading { ProgressView() } } } $BTF࠶ಡΈࠐΈத΋σʔλΛදࣔ#FGPSF $BTFͷFOVNͰ࣮૷ MPBEJOHʹ͸ σʔλ͕ͳ͍

$BTF࠶ಡΈࠐΈத΋σʔλΛදࣔ"GUFS SF-PBEJOH 7 Λ௥Ճ enum DataState<V, E: Error> { case
idle case loading case success(V) case failure(E) } @State private var dataState: DataState<User, any Error> = .idle

idle case loading case reLoading(V) case success(V) case failure(E) } @State private var dataState: DataState<User, any Error> = .idle

idle case initialLoading case reLoading(V) case success(V) case failure(E) } @State private var dataState: DataState<User, any Error> = .idle

$BTF࠶ಡΈࠐΈத΋σʔλΛදࣔ"GUFS 7JFXͷग़͠Θ͚ var body: some View { List { switch
dataState { case .idle, .loading: EmptyView() case .success(let value): content(user: value) case .failure: ErrorStateView() } } .overlay { if dataState.isInitialLoading { ProgressView() } } }

$BTF࠶ಡΈࠐΈத΋σʔλΛදࣔ"GUFS 7JFXͷग़͠Θ͚ var body: some View { List { switch
dataState { case .idle, .initialLoading: EmptyView() case .success(let value), .reLoading(let value): content(user: value) case .failure: ErrorStateView() } } .overlay { if dataState.isInitialLoading { ProgressView() } } } ࠶ಡΈࠐΈத΋ σʔλΛදࣔ

func fetchUser() async { if dataState.isLoading { return } dataState
= .loading do { dataState = .success(try await API.getUser()) } catch { dataState = .failure(error) } } $BTF࠶ಡΈࠐΈத΋σʔλΛදࣔ"GUFS ঢ়ଶૢ࡞

$BTF࠶ಡΈࠐΈத΋σʔλΛදࣔ"GUFS ঢ়ଶૢ࡞ func fetchUser() async { switch dataState { case
.idle, .failure: dataState = .initialLoading case .success(let value): dataState = .reLoading(value) case .initialLoading, .reLoading: return } do { dataState = .success(try await API.getUser()) } catch { dataState = .failure(error) } }

$BTF࠶ಡΈࠐΈத΋σʔλΛදࣔ"GUFS ঢ়ଶૢ࡞ func fetchUser() async { switch dataState { case
.idle, .failure: dataState = .initialLoading case .success(let value): dataState = .reLoading(value) case .initialLoading, .reLoading: return } do { dataState = .success(try await API.getUser()) } catch { dataState = .failure(error) } } TVDDFTT͔Βϩʔυ͢Δ࣌͸ SF-PBEJOH

$BTF࠶ಡΈࠐΈத΋σʔλΛදࣔ"GUFS ঢ়ଶૢ࡞ func fetchUser() async { if dataState.isLoading { return
} dataState.startLoading() do { dataState = .success(try await API.getUser()) } catch { dataState = .failure(error) } } extension DataState { mutating func startLoading() { switch self { case .idle, .failure: self = .initialLoading case .success(let value): self = .reLoading(value) default: return } } }

$BTF࠶ಡΈࠐΈத΋σʔλΛදࣔ"GUFS ঢ়ଶૢ࡞ func fetchUser() async { if dataState.isLoading { return
} dataState.startLoading() do { dataState = .success(try await API.getUser()) } catch { dataState = .failure(error) } }

$BTF࠶ಡΈࠐΈத΋σʔλΛදࣔ"GUFS ࣮૷׬ྃ var body: some View { List { switch
dataState { case .idle, .initialLoading: EmptyView() case .success(let value), .reLoading(let value): content(user: value) case .failure: ErrorStateView() } } .overlay { if dataState.isInitialLoading { ProgressView() } } }

$BTF ࠶ಡΈࠐΈதͰ΋ΤϥʔΛදࣔ

$BTF࠶ಡΈࠐΈதͰ΋ΤϥʔΛදࣔ ཧ૝ͷڍಈ

$BTF࠶ಡΈࠐΈதͰ΋ΤϥʔΛදࣔ ཧ૝ͷڍಈ ϩʔυͱΤϥʔ͕ ಉ࣌ʹදࣔ

#FGPSF

$BTF࠶ಡΈࠐΈதͰ΋ΤϥʔΛදࣔ#FGPSF $BTFͷFOVNͰ࣮૷ enum DataState<V, E: Error> { case idle case
initialLoading case reLoading(V) case success(V) case failure(E) } @State private var dataState: DataState<User, any Error> = .idle

$BTF࠶ಡΈࠐΈதͰ΋ΤϥʔΛදࣔ#FGPSF $BTFͷFOVNͰ࣮૷ var body: some View { List { switch
dataState { case .idle, .initialLoading: EmptyView() case .success(let value), .reLoading(let value): content(user: value) case .failure: ErrorStateView() } } .overlay { if dataState.isInitialLoading { ProgressView() } } }

dataState { case .idle, .initialLoading: EmptyView() case .success(let value), .reLoading(let value): content(user: value) case .failure: ErrorStateView() } } .overlay { if dataState.isInitialLoading { ProgressView() } } } ɾϩʔυதͩͱΤϥʔ͕ফ͑Δ ɾϓϧϦϑͱೋॏʹϩʔυ͕දࣔ

dataState { case .idle, .initialLoading: EmptyView() case .success(let value), .reLoading(let value): content(user: value) case .failure: ErrorStateView() } } .overlay { if dataState.isInitialLoading { ProgressView() } } } JOJUJBM-PBEJOHʹ͸Τϥʔ͕ͳ͍

$BTF࠶ಡΈࠐΈதͰ΋ΤϥʔΛදࣔ"GUFS SFUSZ-PBEJOH & Λ௥Ճ enum DataState<V, E: Error> { case
idle case initialLoading case reLoading(V) case success(V) case failure(E) } @State private var dataState: DataState<User, any Error> = .idle

$BTF࠶ಡΈࠐΈதͰ΋ΤϥʔΛදࣔ"GUFS SFUSZ-PBEJOH & Λ௥Ճ enum DataState<V, E: Error> { case
idle case initialLoading case reLoading(V) case retryLoading(E) case success(V) case failure(E) } @State private var dataState: DataState<User, any Error> = .idle

case .idle, .initialLoading: EmptyView() case .success(let value), .reLoading(let value): content(user: value) case .failure: ErrorStateView() } } .overlay { if dataState.isInitialLoading { ProgressView() } } } $BTF࠶ಡΈࠐΈதͰ΋ΤϥʔΛදࣔ"GUFS 7JFXͷग़͠Θ͚

$BTF࠶ಡΈࠐΈதͰ΋ΤϥʔΛදࣔ"GUFS 7JFXͷग़͠Θ͚ var body: some View { List { switch
dataState { case .idle, .initialLoading: EmptyView() case .success(let value), .reLoading(let value): content(user: value) case .failure, .retryLoading: ErrorStateView() } } .overlay { if dataState.isInitialLoading { ProgressView() } } } ࠶ಡΈࠐΈத΋ ΤϥʔΛදࣔ

$BTF࠶ಡΈࠐΈதͰ΋ΤϥʔΛදࣔ"GUFS ঢ়ଶૢ࡞ func fetchUser() async { if dataState.isLoading { return
} dataState.startLoading() do { dataState = .success(try await API.getUser()) } catch { dataState = .failure(error) } }

$BTF࠶ಡΈࠐΈதͰ΋ΤϥʔΛදࣔ"GUFS ঢ়ଶૢ࡞ func fetchUser() async { if dataState.isLoading { return
} dataState.startLoading() do { dataState = .success(try await API.getUser()) } catch { dataState = .failure(error) } } extension DataState { mutating func startLoading() { switch self { case .idle: self = .initialLoading case .success(let value): self = .reLoading(value) case .failure(let error): self = .retryLoading(error) default: return } } } GBJMVSF͔Βϩʔυ͢Δ࣌͸ SFUSZ-PBEJOH

$BTF࠶ಡΈࠐΈதͰ΋ΤϥʔΛදࣔ"GUFS ࣮૷׬ྃ var body: some View { List { switch
dataState { case .idle, .initialLoading: EmptyView() case .success(let value), .reLoading(let value): content(user: value) case .failure, .retryLoading: ErrorStateView() } } .overlay { if dataState.isInitialLoading { ProgressView() } } }

ঢ়ଶ͕૿͑ͯෳࡶʹͳͬͨʁ enum DataState<V, E: Error> { case idle case initialLoading
case reLoading(V) case retryLoading(E) case success(V) case failure(E) }

ঢ়ଶΛਤղͯ͠ΈΔ

ঢ়ଶΛਤղͯ͠ΈΔ $BTFMPBEJOH

ঢ়ଶΛਤղͯ͠ΈΔ $BTFSF-PBEJOH

ঢ়ଶΛਤղͯ͠ΈΔ $BTFSFUSZ-PBEJOH

ঢ়ଶΛਤղͯ͠ΈΔ

࣮͸MPBEJOHͷ෼ྨΛม͚͑ͨͩ w MPBEJOHΛηϚϯςΟοΫʹ෼ྨ w ʮͲͷঢ়ଶ͔Βϩʔυ͔ͨ͠ʯͰࡉ෼Խ w දݱྗͷ޲্

࣮͸MPBEJOHͷ෼ྨΛม͚͑ͨͩ w MPBEJOHΛηϚϯςΟοΫʹ෼ྨ w ʮͲͷঢ়ଶ͔Βϩʔυ͔ͨ͠ʯͰࡉ෼Խ w දݱྗͷ޲্ w $BTF ͷFOVN͸ʮ؆ུԽ͞Εͨܗʯͱ΋ݴ͑Δ

࠷దͳཻ౓બ୒Λ w MPBEJOHͷ෼ྨ͕ࡉ͔͍ํ͕ରԠͰ͖Δέʔε͕ଟ͍

࠷దͳཻ౓બ୒Λ w MPBEJOHͷ෼ྨ͕ࡉ͔͍ํ͕ରԠͰ͖Δέʔε͕ଟ͍ w ͕ɺ෼ྨ͕ࡉ͔͍෺͕ৗʹྑ͍Θ͚Ͱ͸ͳ͍ w ར༻͠ͳ͍ঢ়ଶΛ͍࣋ͬͯͯ΋࢓ํ͕ͳ͍

࠷దͳཻ౓બ୒Λ w MPBEJOHͷ෼ྨ͕ࡉ͔͍ํ͕ରԠͰ͖Δέʔε͕ଟ͍ w ͕ɺ෼ྨ͕ࡉ͔͍෺͕ৗʹྑ͍Θ͚Ͱ͸ͳ͍ w ར༻͠ͳ͍ঢ়ଶΛ͍࣋ͬͯͯ΋࢓ํ͕ͳ͍ w ࠷దͳMPBEJOHͷ෼ྨͷཻ౓Λબ୒͢΂͠ w
࢓༷ɾকདྷͷ֦ுੑɾՄಡੑɾϩδοΫ؅ཧίετFUDʜ

$BTF ϖʔδϯά

$BTFϖʔδϯά ཧ૝ͷڍಈ

$BTFϖʔδϯά ཧ૝ͷڍಈ ϖʔδϯάத ϖʔδϯάࣦഊͰ΋ લϖʔδͷσʔλ͕දࣔ

$BTFϖʔδϯά QBHJOH 7 QBHJOH'BJMVSF 7 & Λ௥Ճ enum DataState<V, E:
Error> { case idle case initialLoading case reLoading(V) case retryLoading(E) case success(V) case failure(E) } @State private var dataState: DataState<[Post], any Error> = .idle

$BTFϖʔδϯά QBHJOH 7 QBHJOH'BJMVSF 7 & Λ௥Ճ enum DataState<V, E:
Error> { case idle case initialLoading case reLoading(V) case retryLoading(E) case success(V) case failure(E) case paging(V) case pagingFailure(V, E) } @State private var dataState: DataState<[Post], any Error> = .idle

$BTFϖʔδϯά QBHJOH 7 QBHJOH'BJMVSF 7 & Λ௥Ճ enum PagingDataState<V, E:
Error> { case idle case initialLoading case reLoading(V) case retryLoading(E) case success(V) case loadingFailure(E) case paging(V) case pagingFailure(V, E) } @State private var dataState: PagingDataState<[Post], any Error> = .idle

$BTFϖʔδϯά 7JFXͷग़͠Θ͚ var body: some View { List { switch
dataState { case .idle, .initialLoading: EmptyView() case .success(let value), .reLoading(let value): listContent(posts: value) case .failure, .retryLoading: ErrorStateView() } .overlay { if dataState.isInitialLoading { ProgressView() } } }

dataState { case .idle, .initialLoading: EmptyView() case .success(let value), .reLoading(let value): listContent(posts: value) case .failure, .retryLoading: ErrorStateView() } .overlay { if dataState.isInitialLoading { ProgressView() } } } func listContent(posts: [Post]) -> some View { ForEach(posts) { post in Text(post.title) } }

dataState { case .idle, .initialLoading: EmptyView() case .success(let value), .reLoading(let value): listContent(posts: value) case .failure, .retryLoading: ErrorStateView() } .overlay { if dataState.isInitialLoading { ProgressView() } } }

dataState { case .idle, .initialLoading: EmptyView() case .success(let value), .reLoading(let value), .paging(let value), .pagingFailure(let value, _): listContent(posts: value) case .loadingFailure, .retryLoading: ErrorStateView() } .overlay { if dataState.isInitialLoading { ProgressView() } } } ϖʔδϯάதɾϖʔδϯάࣦഊ Ͱ΋લϖʔδͷσʔλΛදࣔ

dataState { case .idle, .initialLoading: EmptyView() case .success(let value), .reLoading(let value), .paging(let value), .pagingFailure(let value, _): listContent(posts: value) case .loadingFailure, .retryLoading: ErrorStateView() } .overlay { if dataState.isInitialLoading { ProgressView() } } }

dataState { case .idle, .initialLoading: EmptyView() case .success(let value), .reLoading(let value), .paging(let value), .pagingFailure(let value, _): listContent(posts: value) if dataState.isPagingFailure { ErrorStateView(…) } else { ProgressView() .onAppear { Task { await fetchMore() } } } case .loadingFailure, .retryLoading: ErrorStateView() -JTUԼ෦ʹ Τϥʔදࣔ ϖʔδϯάݕ஌

$BTFϖʔδϯά ঢ়ଶૢ࡞ʢॳճऔಘɾϦϑϨογϡʣ func fetchInitial() async { if dataState.isLoading || dataState.isPaging
{ return } dataState.startLoading() do { dataState = .success(try await API.getPosts(minId: 0, count: 30)) } catch { dataState = .loadingFailure(error) } }

$BTFϖʔδϯά ঢ়ଶૢ࡞ʢॳճऔಘɾϦϑϨογϡʣ func fetchInitial() async { if dataState.isLoading || dataState.isPaging
{ return } dataState.startLoading() do { dataState = .success(try await API.getPosts(minId: 0, count: 30)) } catch { dataState = .loadingFailure(error) } } extension PagingDataState { mutating func startLoading() { switch self { case .idle: self = .initialLoading case .success(let value), .pagingFailure(let value, _): self = .reLoading(value) case .loadingFailure(let error): self = .retryLoading(error) default: return } } } QBHJOH'BJMVSF͔Βϩʔυ͢Δ࣌͸ SF-PBEJOHʹ

$BTFϖʔδϯά ঢ়ଶૢ࡞ʢϖʔδϯάʣ func fetchMore() async { if dataState.isLoading || dataState.isPaging
{ return } guard let users = dataState.value, let lastId = users.last?.id else { return } dataState.startPaging() do { let newUsers = try await API.getPosts(minId: lastId + 1, count: 30) dataState = .success(users + newUsers) } catch { dataState = .pagingFailure(users, error) } }

{ return } guard let users = dataState.value, let lastId = users.last?.id else { return } dataState.startPaging() do { let newUsers = try await API.getPosts(minId: lastId + 1, count: 30) dataState = .success(users + newUsers) } catch { dataState = .pagingFailure(users, error) } } extension PagingDataState { mutating func startPaging() { switch self { case .success(let value), .pagingFailure(let value, _): self = .paging(value) default: return } } }

{ return } guard let users = dataState.value, let lastId = users.last?.id else { return } dataState.startPaging() do { let newUsers = try await API.getPosts(minId: lastId + 1, count: 30) dataState = .success(users + newUsers) } catch { dataState = .pagingFailure(users, error) } } MPBEJOH'BJMVSFͰ͸ͳ͘ QBHJOH'BJMVSF

$BTFϖʔδϯά ࣮૷׬ྃ var body: some View { List { switch
dataState { case .idle, .initialLoading: EmptyView() case .success(let value), .reLoading(let value), .paging(let value), .pagingFailure(let value, _): listContent(posts: value) if dataState.isPagingFailure { ErrorStateView(…) } else { ProgressView() .onAppear { Task { await fetchMore() } } } case .loadingFailure, .retryLoading: ErrorStateView()

$BTFϖʔδϯά ঢ়ଶΛਤղ

FOVNʹΑΔঢ়ଶ؅ཧ ϙΠϯτ w 👍ը໘ͷঢ়ଶɾඇಉظॲཧσʔλΛͭͷม਺Ͱ؅ཧͰ͖Δ

FOVNʹΑΔঢ়ଶ؅ཧ ϙΠϯτ w 👍ը໘ͷঢ়ଶɾඇಉظॲཧσʔλΛͭͷม਺Ͱ؅ཧͰ͖Δ w 👍ΧελϚΠζੑ͕ߴ͍ w ೚ҙͷڍಈɾϩʔυதɾ੒ޭɾࣦഊ7JFXΛग़ͤΔ

FOVNʹΑΔঢ়ଶ؅ཧ ϙΠϯτ w 👍ը໘ͷঢ়ଶɾඇಉظॲཧσʔλΛͭͷม਺Ͱ؅ཧͰ͖Δ w 👍ΧελϚΠζੑ͕ߴ͍ w ೚ҙͷڍಈɾϩʔυதɾ੒ޭɾࣦഊ7JFXΛग़ͤΔ w 👎ϘΠϥʔϓϨʔτ͕ଟൃ
w ࣮ࡍͷ։ൃͰ͸ଟ͘ͷը໘Ͱ౷Ұ͞Ε͍ͯΔέʔε͕ଟ͍

var body: some View { PagingList( success: listContent, fetchInitial: {
try await API.getPosts(minId: 0, count: 30) }, fetchMore: { try await API.getPosts(minId: $0.id + 1, count: 30) } ) } ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ

var body: some View { PagingList( success: listContent, fetchInitial: {
try await API.getPosts(minId: 0, count: 30) }, fetchMore: { try await API.getPosts(minId: $0.id + 1, count: 30) } ) } ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ ඇಉظॲཧΛ౉͢ ϨΠΞ΢τΛ౉͢

ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ ϙΠϯτ w 👍ϘΠϥʔϓϨʔτͷճආ w ίʔυྔͷ࡟ݮ

ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ ϙΠϯτ w 👍ϘΠϥʔϓϨʔτͷճආ w ίʔυྔͷ࡟ݮ w 👎ΧελϚΠζੑ͕௿͍ w ڞ௨ίϯϙʔωϯτͰରԠͰ͖ͳ͍৔߹΋ଘࡏ

FOVN ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ w FOVNΛҾ਺ʹͱΔίϯϙʔωϯτ

FOVN ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ 4XJUDI7JFX4UZMF w ֤ը໘ͰTXJUDIͷϘΠϥʔϓϨʔτΛॻ͘ඞཁੑ w ࣮ࡍͷ։ൃͰ͸ʢଟ͘ͷը໘Ͱʣ࢓༷͕౷Ұ͞Ε͍ͯΔέʔε͕ଟ͍ w ঢ়ଶૢ࡞ͷϛε͕ͳ͍Θ͚Ͱ͸ͳ͍ @State
private var dataState: PagingDataState<[Post], any Error> = .idle var body: some View { PagingList(dataState: dataState, listContent: listContent) { Task { await fetchMore() } } .refreshable { await fetchInitial() } .task { await fetchInitial() } .onChange(of: dataState.isFailure) { bool in guard bool, let error = dataState.error else { return } MessageBanner.showError("Τϥʔ͕ൃੜ͠·ͨ͠", with: error.localizedDescription) } }

FOVN ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ 4XJUDI7JFX4UZMF w ֤ը໘ͰTXJUDIͷϘΠϥʔϓϨʔτΛॻ͘ඞཁੑ w ࣮ࡍͷ։ൃͰ͸ʢଟ͘ͷը໘Ͱʣ࢓༷͕౷Ұ͞Ε͍ͯΔέʔε͕ଟ͍ w ঢ়ଶૢ࡞ͷϛε͕ͳ͍Θ͚Ͱ͸ͳ͍ @State
private var dataState: PagingDataState<[Post], any Error> = .idle var body: some View { PagingList(dataState: dataState, listContent: listContent) { Task { await fetchMore() } } .refreshable { await fetchInitial() } .task { await fetchInitial() } .onChange(of: dataState.isFailure) { bool in guard bool, let error = dataState.error else { return } MessageBanner.showError("Τϥʔ͕ൃੜ͠·ͨ͠", with: error.localizedDescription) } } ϖʔδϯά ϓϧϦϑ ॳճऔಘ ΤϥʔΛόφʔͰදࣔ

'FUDI7JFX4UZMF w ֤ը໘ͰTXJUDIͷϘΠϥʔϓϨʔτΛॻ͘ඞཁੑ w ࣮ࡍͷ։ൃͰ͸ʢଟ͘ͷը໘Ͱʣ࢓༷͕౷Ұ͞Ε͍ͯΔέʔε͕ଟ͍ w ঢ়ଶૢ࡞ͷϛε͕ͳ͍Θ͚Ͱ͸ͳ͍ @StateObject private var
viewStore: LoadingContentViewStore<Post> = .init( fetchInitial: { try await API.getPosts(minId: 0, count: 30) }, fetchMore: { try await API.getPosts(minId: $0.id + 1, count: 30) } ) var body: some View { PagingList(viewStore: viewStore, success: listContent) .task { await viewStore.loadInitial() } .onChange(of: viewStore.dataState.isFailure) { bool in guard bool, let error = viewStore.dataState.error else { return } MessageBanner.showError("Τϥʔ͕ൃੜ͠·ͨ͠", with: error.localizedDescription) } } FOVN ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ

viewStore: LoadingContentViewStore<Post> = .init( fetchInitial: { try await API.getPosts(minId: 0, count: 30) }, fetchMore: { try await API.getPosts(minId: $0.id + 1, count: 30) } ) var body: some View { PagingList(viewStore: viewStore, success: listContent) .task { await viewStore.loadInitial() } .onChange(of: viewStore.dataState.isFailure) { bool in guard bool, let error = viewStore.dataState.error else { return } MessageBanner.showError("Τϥʔ͕ൃੜ͠·ͨ͠", with: error.localizedDescription) } } FOVN ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ ঢ়ଶ؅ཧΛ͢Δ4UBUF0CKFDUΛ౉͢

viewStore: LoadingContentViewStore<Post> = .init( fetchInitial: { try await API.getPosts(minId: 0, count: 30) }, fetchMore: { try await API.getPosts(minId: $0.id + 1, count: 30) } ) var body: some View { PagingList(viewStore: viewStore, success: listContent) .task { await viewStore.loadInitial() } .onChange(of: viewStore.dataState.isFailure) { bool in guard bool, let error = viewStore.dataState.error else { return } MessageBanner.showError("Τϥʔ͕ൃੜ͠·ͨ͠", with: error.localizedDescription) } } FOVN ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ ར༻ऀଆ͔Β΋ൃՐՄೳ

viewStore: LoadingContentViewStore<Post> = .init( fetchInitial: { try await API.getPosts(minId: 0, count: 30) }, fetchMore: { try await API.getPosts(minId: $0.id + 1, count: 30) } ) var body: some View { PagingList(viewStore: viewStore, success: listContent) .task { await viewStore.loadInitial() } .onChange(of: viewStore.dataState.isFailure) { bool in guard bool, let error = viewStore.dataState.error else { return } MessageBanner.showError("Τϥʔ͕ൃੜ͠·ͨ͠", with: error.localizedDescription) } } FOVN ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ ॳճऔಘ΍Τϥʔදࣔ͸ը໘͝ͱ ར༻ऀଆ͔Β΋ൃՐՄೳ

#JOEBCMF'FUDI7JFX4UZMF @State private var dataState: PagingDataState<[Post], any Error> = .idle
var body: some View { PagingList( dataState: $dataState, success: listContent, fetchInitial: { try await API.getPosts(minId: 0, count: 30) }, fetchMore: { try await API.getPosts(minId: $0.id + 1, count: 30) } ) .onChange(of: dataState.isFailure) { isFailure in guard isFailure, let error = dataState.error else { return } MessageBanner.showError("Τϥʔ͕ൃੜ͠·ͨ͠", with: error.localizedDescription) } } FOVN ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ

var body: some View { PagingList( dataState: $dataState, success: listContent, fetchInitial: { try await API.getPosts(minId: 0, count: 30) }, fetchMore: { try await API.getPosts(minId: $0.id + 1, count: 30) } ) .onChange(of: dataState.isFailure) { isFailure in guard isFailure, let error = dataState.error else { return } MessageBanner.showError("Τϥʔ͕ൃੜ͠·ͨ͠", with: error.localizedDescription) } } FOVN ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ #JOEJOHͰঢ়ଶ͚ͩ౉͢

var body: some View { PagingList( dataState: $dataState, success: listContent, fetchInitial: { try await API.getPosts(minId: 0, count: 30) }, fetchMore: { try await API.getPosts(minId: $0.id + 1, count: 30) } ) .onChange(of: dataState.isFailure) { isFailure in guard isFailure, let error = dataState.error else { return } MessageBanner.showError("Τϥʔ͕ൃੜ͠·ͨ͠", with: error.localizedDescription) } } FOVN ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ Τϥʔදࣔ͸ը໘͝ͱ

4JNQMF'FUDI7JFX4UZMF var body: some View { PagingList( success: listContent, fetchInitial:
{ try await API.getPosts(minId: 0, count: 30) }, fetchMore: { try await API.getPosts(minId: $0.id + 1, count: 30) } ) } FOVN ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ

4XJUDI 'FUDI #JOEBCMF'FUDI 4JNQMF'FUDI ঢ়ଶͷૢ࡞   ʢඇಉظॲཧʣ ར༻ऀ👨💻 ಺෦🤖 ར༻ऀ΋Մೳ👨💻
಺෦🤖 ಺෦🤖 ঢ়ଶͷऔಘ Մೳ⭕ Մೳ⭕ Մೳ⭕ ෆՄೳ❌ FOVN ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ

FOVN ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ ؆ܿ͞ ΧελϚΠζੑ 4XJUDI 'FUDI #JOEBCMF'FUDI 4JNQMF'FUDI ঢ়ଶͷૢ࡞  
ʢඇಉظॲཧʣ ར༻ऀ👨💻 ಺෦🤖 ར༻ऀ΋Մೳ👨💻 ಺෦🤖 ಺෦🤖 ঢ়ଶͷऔಘ Մೳ⭕ Մೳ⭕ Մೳ⭕ ෆՄೳ❌

w 👍ϘΠϥʔϓϨʔτΛճආͭͭ͠ɺΧελϚΠζੑ΋͋Δ FOVN ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ

w 👍ϘΠϥʔϓϨʔτΛճආͭͭ͠ɺΧελϚΠζੑ΋͋Δ w 👍σβΠϯͷ౷Ұʹ΋ޮՌత w ϩʔυදࣔΛίϯϙʔωϯτ಺Ͱڞ௨ԽͳͲ w σβΠϯγεςϜͱ΋૬ੑ͕ྑ͍ FOVN ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ

w 👍ϘΠϥʔϓϨʔτΛճආͭͭ͠ɺΧελϚΠζੑ΋͋Δ w 👍σβΠϯͷ౷Ұʹ΋ޮՌత w ϩʔυදࣔΛίϯϙʔωϯτ಺Ͱڞ௨ԽͳͲ w σβΠϯγεςϜͱ΋૬ੑ͕ྑ͍ w ͦΕͰ΋ແཧͳΒFOVNΛ௚ͰTXJUDI
FOVN ίϯϙʔωϯτʹΑΔঢ়ଶ؅ཧ

·ͱΊ w FOVNͷදݱྗΛ্͛Ε͹༷ʑͳ࢓༷ʹରԠՄೳ

·ͱΊ w FOVNͷදݱྗΛ্͛Ε͹༷ʑͳ࢓༷ʹରԠՄೳ w ࠷దͳཻ౓Λબ୒

·ͱΊ w FOVNͷදݱྗΛ্͛Ε͹༷ʑͳ࢓༷ʹରԠՄೳ w ࠷దͳཻ౓Λબ୒ w ଟ͘ͷέʔεͰ͸FOVNΛҾ਺ʹͱΔίϯϙʔωϯτΛར༻ w ϘΠϥʔϓϨʔτΛճආͭͭ͠ɺΧελϚΠζ΋Ͱ͖Δ w
ڍಈɾσβΠϯͷ౷Ұʹ΋ޮՌత w ࠷దͳ࣮૷Λબ୒

ࢀߟ w ϞόΠϧΞϓϦʹ͓͚ΔಡΈࠐΈॲཧपΓͷ6*ύλʔϯͱ4XJGU6*ʹΑΔ࣮૷ྫ w IUUQT[FOOEFWSPDLOBNFBSUJDMFTBFF f w "TZOD w
IUUQTHJUIVCDPNCBOO[BJ"TZOD w #VJMEJOHSFVTBCMFDPOUFOUMPBEJOHWJFXJO4XJGU6* w IUUQTENZUSPBOPLIJONFEJVNDPNCVJMEJOHSFVTBCMFDPOUFOUMPBEJOHWJFXXJUITXJGUVJBOEDPNCJOF GGFFC w 4XJGU6*Ͱʮάϧʔϓελϯϓʯͱ͍͏νϟοτػೳΛ೔ؒͰ࡞ͬͨ࿩ w IUUQTNFEJVNDPNLBVDIFTXJGUVJHSPVQDIBUDEF

ࣗݾ঺հ LOUL w έʔΤψςΟʔέʔ w ໊ݹ԰޻ۀେֶ. w དྷ೥͔ΒJ04ΤϯδχΞ w J04%$-5ొஃ

IUUQT[FOOEFWLOULBSUJDMFTGCEBGF

͓·͚ IUUQTHJUIVCDPNLOULZNU"TZOD%BUB.BOBHFNFOU4BNQMFT IUUQT[FOOEFWLOULBSUJDMFTEBEBEG

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͓·͚ IUUQTHJUIVCDPNLOULZNU"TZOD%BUB.BOBHFNFOU4BNQMFT IUUQT[FOOEFWLOULBSUJDMFTEBEBEG

SwiftUIでの非同期処理データの状態管理を考える

SwiftUIでの非同期処理データの状態管理を考える

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