健康的なMVVM 書いてますか？ ~MVVMアンチパターン集~

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͓͞Β͍ .77.ͱ͸

.PEFM 7JFX.PEFM 7JFX %BUB #JOEJOH $PNNBOET ɹ%BUB#JOEJOHͷ࣮ݱͷͨΊʹ͸ɺJ04ͷ৔߹ ɹɹ'31ϥΠϒϥϦ 3Y4XJGU 3FBDUJWF$PDPB
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͜Ε͔Β  ෆ݈߁ͳ7JFX.PEFMΛ  ਍࡯͠·͢

Ͱ͠Ό͹Γ7JFX.PEFM Χϧςᶃ 

class MyViewModel { weak var view: MyView? func doSomething(fuga: Fuga)
{ guard let view = view else { return } if view.isHoge { view.doSomething(fuga) } } } class MyView { func awakeFromNib() { viewModel.view = self } } Ͱ͠Ό͹Γ7JFX.PEFM ঱ঢ় 7JFX.PEFM͕7JFX΁ͷࢀরΛ࣋ͬͯɺ௚઀ૢ࡞͢Δ

Ͱ͠Ό͹Γ7JFX.PEFM පࠜ   ࠜຊతʹઃܭ͕͓͔͍͠ w 7JFXʹमਖ਼͕ೖͬͨΒ7JFX.PEFM΋मਖ਼͠ͳ͖Όʜ w ͔ͤͬ͘ͷ.77.ύλʔϯ͕୆ແͩ͠ʂ w ʜͱ͍͏͔ɺ͜Ε.77.ʹͳͬͯͳ͍

ґଘͷํ޲͸ 7JFXɹɹ7JFX.PEFM 7JFX.PEFMɹɹ.PEFM Ҿ༻"SDIJUFDUJOH"OESPJEʜ5IFDMFBOXBZ   IUUQGFSOBOEPDFKBTDPNBSDIJUFDUJOHBOESPJEUIFDMFBOXBZ 7JFX.PEFM 7JFX σʔλόΠϯσΟϯά

Ͱ͠Ό͹Γ7JFX.PEFM ॲํᝦ w 7JFX.PEFM͸ࣗ෼ࣗ਎ͷঢ়ଶΛมߋ͢Δ͚ͩ w Ͳ͏࢖ΘΕΔ͔͸Ұ੾ؔ஌͠ͳ͍͠ɺ  ୭ 7JFX ʹόΠϯυ͞Ε͍ͯΔ͔΋஌Βͳ͍  ʹ7JFXʹґଘ͠ͳ͍ 
ʹมߋʹڧ͍ 7JFX.PEFMˠ7JFX͸ ඞͣόΠϯσΟϯάͰܨ͙

class MyViewModel { let fuga = Observable<Fuga?>(nil) func didReceiveFuga(fuga: Fuga)
{ self.fuga.value = fuga } } class MyView { func awakeFromNib() { viewModel.fuga.ignoreNil().observe { [weak self] in self?.doSomething($0) } } } Ͱ͠Ό͹Γ7JFX.PEFM վળྫ

ࠞઢ͍ͯ͠Δ 7JFX.PEFM Χϧςᶄ 

ࠞઢ͍ͯ͠Δ7JFX.PEFM ঱ঢ় 7JFX.PEFM΁ͷίϚϯυ͕  ɹॲཧͷ׬ྃ࣌ʹ࣮ߦ͢ΔΫϩʔδϟΛड͚ͨΓ class MyView { func awakeFromNib() {
viewModel.alertMessage.observe { [weak self] in self?.showAlert($0) // ↓Ͳ͕ͬͪຊے!? } } func didTapButton() { viewModel.doSomething(completion: { [weak self] alertMessage in self?.showAlert(alertMessage) // ↑Ͳ͕ͬͪຊے!? }) } } ˠॲཧͷྲྀΕ͕ΧΦεʹʂ BMFSU.FTTBHF 0CTFSWBCMF4USJOH͕ มߋ͞ΕͨΒൃಈ ͳΜ͔΍ͬͨ݁Ռ BMFSU.FTTBHFΛ ड͚औΔ

ࠞઢ͍ͯ͠Δ7JFX.PEFM පࠜ  ॲཧͷྲྀΕ͕ ੔ཧͰ͖͍ͯͳ͍

ࠞઢ͍ͯ͠Δ7JFX.PEFM ॲํᝦ جຊɺ  7JFXˠ7JFX.PEFM͸ίϚϯυΛୟ͚ͩ͘ 7JFX.PEFMˠ7JFX͸όΠϯυ͢Δ͚ͩ 7JFX.PEFM 7JFX %BUB #JOEJOH $PNNBOET
ᶃίϚϯυ ᶄঢ়ଶมߋ ᶅঢ়ଶ൓ө †એݴతʹهड़

Ψϥεͷ7JFX.PEFM Χϧςᶅ 

class MyViewModel { let text = Observable<String>("") let textLength =
Observable<Int>(0) } vm.text.value = "ͳΜ͔௕͍ςΩετ" vm.text // "ͳΜ͔௕͍ςΩετ" vm.textLength // 0 ←!!?!!? Ψϥεͷ7JFX.PEFM ঱ঢ় յΕͦ͏ͳ0CTFSWBCMF͹͔ΓूΊͯ͠·͏

Ψϥεͷ7JFX.PEFM පࠜ  ঢ়ଶͷओैؔ܎Λ  એݴతʹදݱͰ͖͍ͯͳ͍ w UFYUΛมߋͨ͠Βɺ  ͦͷϝιουͰUFYU-FOHUI΋  มߋ͢ΔΑ͏ʹؾΛ͚ͭΔʁ  ͍΍͍΍ɺͦΜͳͷਓ͕ؒ  έΞ͢΂͖͜ͱ͡Όͳ͍͔Βʂ
ຖճҪށ͔Β ਫΛ἞·͞ΕͯΔΑ͏ͳ ॏ࿑ಇײ

Ψϥεͷ7JFX.PEFM ॲํᝦ $PMEͳ0CTFSWBCMFΛ࢖͏ )PU  0CTFSWBCMF $PME  &WFOU1SPEVDFS

class MyViewModel { let text = Observable<String>("") let textLength: EventProducer<Int>
init() { textLength = text.map { $0.characters.count } } } vm.text // "ͳΜ͔௕͍ςΩετ" vm.textLength // 9 Ψϥεͷ7JFX.PEFM վળྫ ɹUFYU-FOHUI͸NBQ USBOTGPSNJOHPQFSBUPS Λ௨͚ͩ͢ͷ ɹ$PMEͳଘࡏʹ͠ɺ੔߹ੑΛอূ એݴతʹهड़Ͱ͖ͨʂ

ઉ଍Βͣͳ  7JFX.PEFM Χϧςᶆ 

class MyViewModel { let name = Observable<String>("") let address =
Observable<String>("") } let vm = MyViewModel() vm.name.observe { func setUserData() } vm.address.observe { func setUserData() } func setUserData(userId: Int) { userNameLabel.text = vm.name userAddressLabel.text = vm.address } ઉ଍Βͣͳ7JFX.PEFM ঱ঢ় ɹ7JFX.PEFMͷมԽΛड͚औͬͨ7JFX͕ɺ  ɹվΊͯ7JFX.PEFMͷϓϩύςΟΛࢀর͍ͯ͠Δ OBNFͱBEESFTT ͲͪΒ͕มߋ͞Εͯ΋ ྆ํΛ࢖ͬͯߋ৽ॲཧΛ ߦ͍͍ͨʂ

ઉ଍Βͣͳ7JFX.PEFM පࠜ σʔλΛద੾ͳཻ౓ɾ૊Ͱ ౉͍ͯ͠ͳ͍

ઉ଍Βͣͳ7JFX.PEFM ॲํᝦ ֤छΦϖϨʔλΛ࢖͍͜ͳ͢ class MyViewModel { let name = Observable<String>("")
let address = Observable<String>("") lazy var nameAndAddress: EventProducer<(String, String)> = { return combineLatest(self.name, self.address) }() } let vm = MyViewModel() vm.nameAndAddress.observe { name, address in userNameLabel.text = name userAddressLabel.text = address } IUUQSYNBSCMFTDPNͱ͔ࢀߟʹͳΔΑ OBNFͱBEESFTT͕ λϓϧͰ౉ͬͯ͘Δ

؂ಜෆߦಧͳ  7JFX.PEFM Χϧςᶇ 

class MyView { var viewType: ViewType func setup(viewType: ViewType) {
self.viewType = viewType switch viewType { case .Title: viewModel.title.observe { ... } case .Image: viewModel.image.observe { ... } case .Detail: viewModel.detail.observe { ... } } } } ؂ಜෆߦಧͳ7JFX.PEFM ঱ঢ় 7JFXଆʹঢ়ଶ΍৚݅෼ذ͕͋Δ

؂ಜෆߦಧͳ7JFX.PEFM පࠜ  ঢ়ଶ΍৚݅൑அͷίʔυΛ  7JFX.PEFMʹҠ͍ͯ͠ͳ͍

ͦ΋ͦ΋7JFX.PEFM͸.PEFMͷӨͳͷͰ͢ɻ  ͦͯ͠·ͨ7JFX͸7JFX.PEFMͷӨͰ΋͋Γ·͢ɻ Ҿ༻.77.ͷ.PEFMʹ·ͭΘΔޡղUIFTFBPGGFSUJMJUZ IUUQVHBZBIBUFCMPKQFOUSZNPEFMNJTUBLF

؂ಜෆߦಧͳ7JFX.PEFM ॲํᝦ ʮ7JFX͸7JFX.PEFMͷӨʯΛ పఈͤ͞Δ class MyView { func awakeFromNib() {
viewModel.title.observe { ... } viewModel.image.observe { ... } viewModel.detail.observe { ... } } } 7JFX͸Կ΋൑அΛߦΘͣɺ 7JFX.PEFMͷঢ়ଶΛ ໧ʑͱ6*ʹ൓өͤ͞Δ 7JFX.PEFM͸ɺ 7JFXΛ࠶ߏ੒Ͱ͖Δ͚ͩͷ ঢ়ଶ৘ใΛอ࣋͢Δ

ਆܦ࣭ͳ  7JFX.PEFM Χϧςᶈ 

ਆܦ࣭ͳ7JFX.PEFM ঱ঢ় 7JFX.PEFM͕ঢ়ଶΛࡉ͔࣋ͪ͗ͯ͘͢ΧΦε ɾμΠΞϩάͷදࣔඇදࣔঢ়ଶͱ͔ ɾը໘ભҠͷঢ়ଶͱ͔

ਆܦ࣭ͳ7JFX.PEFM පࠜ ʮঢ়ଶʯͱʮشൃੑͷݱ৅ʯΛ ۠ผͰ͖͍ͯͳ͍ ˞شൃੑͷݱ৅ඞͣফ͑Ώ͘΋ͷɻ

ਆܦ࣭ͳ7JFX.PEFM ॲํᝦ 0CTFSWBCMF7PJE class MyViewModel { let isUpdated = Observable<Void>()
private func didSomething() { isUpdated.next() } } 81' 8JOEPXT1SFTFOUBUJPO'PVOEBUJPO ʹ͸ .FTTFOHFSͱ͍͏֓೦͕͋Δ  7JFX.PEFM͕Πϕϯτͷൃߦͱ͍͏ܗͰ7JFXʹ௨஌͢Δ࢓૊Έ ղܾ͍ͨ͠໰୊͸ಉ͡ʜ ͩͱࢥ͏Μ͚ͩͲɺ 81'ͷ஌ݟ͕ͳ͍ͷͰ ؒҧͬͯͨΒ͢Έ·ͤΜʜ ͱΓ͋͑ͣ 0CTFSWBCMF7PJE͸ศརͰ͢

ϝλϘϦοΫγϯυϩʔϜ  7JFX.PEFM Χϧςᶉ 

ϝλϘͳ7JFX.PEFM ঱ঢ় 7JFX.PEFM͕  ɹ ɹ௨৴ॲཧ  ɹσʔλΩϟογϡ  ɹ͞·͟·ͳۀ຿ͷϋϯυϦϯά   ɹʜΛߦ͍ͬͯΔ

ϝλϘͳ7JFX.PEFM පࠜ .PEFMʹ͍ͭͯ ޡղͯ͠·ͤΜ͔

ϝλϘͳ7JFX.PEFM ॲํᝦ .PEFM૚Λ͔ͬ͠Γ࡞Ζ͏ .PEFM%"0 %BUB"DDFTT0CKFDU Ͱ͸ͳ͍ .PEFMۀ຿ϩδοΫ ඇ6*,JUͷผϓϥοτϑΥʔϜʹҠ২ͯ͠΋มΘΒͳ͍෦෼ Α͘7JFX$POUSPMMFSʹߦ͘Β͍ॻ͔ΕͯΔ΍ͭ ͋Ε͸΄ͱΜͲ.PEFMʹॻ͘΂͖΋ͷ

;ͨͨͼҾ༻"SDIJUFDUJOH"OESPJEʜ5IFDMFBOXBZ   IUUQGFSOBOEPDFKBTDPNBSDIJUFDUJOHBOESPJEUIFDMFBOXBZ .77.͸ ΞʔΩςΫνϟશମΛΧόʔͰ͖Δ֓೦Ͱ͸ͳ͘ ද૚෦෼ͷ࣮૷ʹա͗ͳ͍

.PEFM 7JFX.PEFM 7JFX %BUB #JOEJOH $PNNBOET ͜ͷ࿈ܞʹ͍ͭͯ͸.77.͸Կ΋نఆͯ͠ͳ͍ ʢ.7˓શ෦ͦ͏͚ͩͲʣ

ͦ͏͍͏ͱ͜Λҙࣝͭͭ͠ɺ ΞϓϦશମʹ໨Λ഑ͬͯ ݈߁తͳઃܭΛ͠ɺ ݈߁తͳίʔυΛॻ͖ɺ ݈߁తͳΤϯδχΞϥΠϑΛૹΓ·͠ΐ͏ʂ

'J/$Ͱ͸ ݈߁తͳΤϯδχΞ஥ؒΛืू͍ͯ͠·͢

健康的なMVVM 書いてますか？ ~MVVMアンチパターン集~

健康的なMVVM 書いてますか？ ~MVVMアンチパターン集~

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