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Kotlin頻出表現
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Moyuru Aizawa
November 28, 2016
Programming
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260
Kotlin頻出表現
Kotlinでよくつかう文/式等
TwitterID変えました。@lvla0805 -> @MoyuruAizawa
Moyuru Aizawa
November 28, 2016
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Transcript
,PUMJOසग़දݱ !MWMB
lvla lvla0805 Ѫᖒ๖ .PZVSV"J[BXB -FBEFOHJOFFSPGQBJST%JWFVSFLB *OD FVSFLB,PUMJO&WBOHFMJTU
+BWB,PUMJO3Y+BWB
None
QBJST $PVQMFT NBUDIHSPVQ *"$ OPXIJSJOH
None
NFFUT
WBM
‣ SFBEPOMZ ‣ جຊWBMΛར༻͍ͯ͠Δɻ ‣ ňͦΕWBSͰ͋Δඞཁ͋Δͷ ʼn ‣ ΈΜͳ+BWBॻ࣌͘ʹpOBMΛ͚ͭΔΑ͏ʹͳͬͨ WBM
val readOnliy = 10 readOnliy = 20 // error
/VMMBCMF
‣ /VMMΛڐ༰͢Δܕͱɺ/VMMΛڋ൱͢Δܕ͕໌֬ʹΘ͚ΒΕ͍ͯΔ ‣ OPU/VMMʹOVMMೖͰ͖ͳ͍͠ɺOVMMBCMFΛೖ͢Δ͜ͱग़དྷͳ ͍ ‣ ৗʹ/VMMΛҙࣝͯ͠ίʔσΟϯά͢Δ͜ͱʹͳΔ /VMMBCMF val nullable:
String? = null var notNull: String = null // error notNull: String = nullable // error
4BGF$BMM
‣ /VMMBCMF͕/VMMͷ߹ɺOVMM͕ฦ٫͞ΕΔɻ ‣ /VMMBCMF͕/VMMͰͳ͍߹ɺ͕࣮ؔߦ͞ΕΔϓϩύςΟͷ͕ฦ٫ ͞ΕΔɻ 4BGF$BMM nullablePerson?.toString() nullablePerson?.age
%FMFHBUFE1SPQFSUJFT
‣ ϓϩύςΟͷॳظԽΛҕৡͰ͖Δ ‣ ॳظԽΛԆͰ͖Δ ‣ ϥΠϑαΠΫϧʹґଘ͢ΔͷͰWBMͰॳظԽͰ͖Δ %FMFHBUFE1SPQFSUJFT val view by
bindView(R.id.view) val string by lazy { getString(R.string.foo) }
&YUFOTJPO'VODUJPO
‣ ܧঝ͢Δࣄͳ͘ɺطଘΫϥεʹؔΛՃͰ͖Δɻ &YUFOTJPO'VODUJPO fun Activity.toWeb(uri: Uri) { startActivity( Intent(Intent.ACTION_VIEW, uri)
) } fun Subscription.addTo(subscriptions: CompositeSubscription) { subscriptions(this) }
4JOHMF&YQSFTTJPO'VODUJPO
‣ ؔͷ࣮͕୯Ұࣜͷ߹ɺฦΓͷએݴɺϒϩοΫɺSFUVSOΛলུ Ͱ͖Δɻ 4JOHMF&YQSFTTJPO'VODUJPO @Provide fun provideApplicationContext() = applicationContext
)JHIFS0SEFS'VODUJPO
‣ ؔΛҾʹͱͬͨΓ ‣ ؔΛฦ٫͢Δؔ ‣ +BWB͕ؔϑΝʔετΫϥεΦϒδΣΫτ͡Όͳ͍͔Β͜Ε͕Ͱ͖ ͳ͍ )JHIFS0SEFS'VODUJPO fun foo(
function: (Int)->Unit ) { … } fun bar(): (Int)->String { … }
‣ 7JFXΛҾʹͱΓ6OJU 㲈7PJE Λฦ٫͢ΔؔͱಉͰ 4". public interface OnClickListener { void
onClick(View var1); }
‣ ؔͭͷΠϯλʔϑΣʔεΛҾʹऔΔؔʹɺؔΛͤ·͢ ‣ هड़ྔΊͬͪΌݮΔʜ 4". view.setOnClickListener({ view -> view.visibility =
View.GONE }) view.setOnClickListener { view -> view.visibility = View.GONE } view.setOnClickListener { it.visibility = View.GONE }
MFU
‣ ؔΛ͢ͱɺͦͷؔΛ࣮ߦͯ͘͠ΕΔɻ ‣ 4BGF$BMMͰMFUΛ࣮ߦ͍ͯ͠ΔͷͰɺOVMMͰͳ͍߹ʹͷΈ࣮ߦ͞Ε Δɻ MFU nullable?.let { it.doSomething }
BQQMZ
‣ Ϩγʔό 'PP'SBHNFOU ͷϓϩύςΟؔΛར༻͢ΔؔΛ͢ ‣ ͦΕΒ͕ద༻͞ΕͨϨγʔό͕ฦ٫͞ΕΔɻ BQQMZ FooFragment().apply { arguments
= Bundle().apply { pustString("key", "value") } }
‣ 4JOHMF&YQSFTTJPO'VODUJPOͱΈ߹ΘͤΔͱ͖ͬ͢Γ BQQMZ fun newInstance() = FooFragment().apply { arguments =
Bundle().apply { pustString("key", "value") } }
EFDMBSJOHQSPQFSUJFTBOE JOJUJBMJ[JOHUIFNGSPNQSJNBSZ DPOTUSVDUPS
‣ ϓϩύςΟͷએݴͱॳظԽΛɺϓϥΠϚϦίϯετϥΫλͰߦ͑Δ ‣ ϗϯτָʜ EFDMBSJOHQSPQFSUJFTBOEJOJUJBMJ[JOHUIFNGSPNQSJNBSZDPOTUSVDUPS class Person(val firstName: String, val
lastName: String, var age: Int) { // ... }
%BUB$MBTT
‣ FRVBMT IBTI$PEF UP4USJOH DPQZ ΛίϯύΠϧ࣌ʹੜͯ͠ ͘ΕΔ ‣ Ξοϓσʔτ͞Εͳ͍FRVBMT ͱ͞Α͏ͳΒͰ͖Δɻ
%BUB$MBTT data class Person(val firstName: String, val lastName: String, var age: Int)
OUBSPLOJU
‣ ֦ுؔΛͬͯBTTFSU5IBUΛ͍͍ײ͡ʹͯ͘͠ΕΔ ‣ ͏͜Ε͕ͳ͍ͱςετॻ͚ͳ͍ʜ LOJU @Test fun test() { (1
+ 2).should be 3 // assertThat(1 + 2, `is`(3)) }
TZTZBHJLNPDLJUP
‣ ֦ுؔΛͬͯNPDLJUPΛ͍͍ײ͡ʹͯ͘͠ΕΔɻ ‣ ͜Εͳ͍ͱςετͰ͖ͳ͍ʜ LNPDLJUP var item: Item = mock()
item.length().invoked.thenReturn(10) item.length().should be 10 item.verify().length()
5IBOLZPV