Delegated propertyで Android開発をもっと便利に @ Gunosy Beer Bash #12

%FMFHBUFEQSPQFSUZͰ "OESPJE։ൃΛ΋ͬͱศརʹ (VOPTZ#FFS#BTI גࣜձࣾτΫόΠ ઍ༿ོ༤

w ઍ༿ོ༤ !DIJCBUDIJOH w גࣜձࣾτΫόΠ w "OESPJEΤϯδχΞ ࣗݾ঺հ

w /VMM҆શ w ֦ுؔ਺ w WBSWBM ,PUMJOͱ͍͑͹ʁ

w /VMM҆શ w ֦ுؔ਺ w WBSWBM w %FMFHBUFE1SPQFSUZ ,PUMJOͱ͍͑͹ʁ

%FMFHBUFE1SPQFSUZ

w ϓϩύςΟͷHFUUFSTFUUFSॲཧΛ ผͷΫϥεΦϒδΣΫτʹҕৡͰ͖Δ ࢓૊Έ w CZΩʔϫʔυͰҕৡઌΛࢦఆ͢Δ %FMFHBUFE1SPQFSUZ

ҕৡ͢Δଆ var foo1: String by Foo() var foo2: String by
getFoo() fun getFoo() = Foo() fun main(vararg args: String) { var foo2: String by getFoo() } CZͷޙΖʹҕৡઌͷ ΫϥεΠϯελϯε

ҕৡ͢Δଆ var foo1: String by Foo() var foo2: String by
getFoo() fun getFoo() = Foo() fun main(vararg args: String) { var foo2: String by getFoo() } CZͷޙΖʹҕৡઌͷ ΫϥεΠϯελϯε ҕৡઌΛฦ͢ ؔ਺Ͱ΋Մ

ҕৡ͞ΕΔଆ var foo1: String by Foo() var foo2: String by
getFoo() fun getFoo() = Foo() fun main(vararg args: String) { var foo2: String by getFoo() } CZͷޙΖʹҕৡઌͷ ΫϥεΠϯελϯε ҕৡઌΛฦ͢ ؔ਺Ͱ΋Մ ,PUMJO͔Β͸ ϩʔΧϧม਺Ͱ΋ར༻Մೳʹʂ

ҕৡ͞ΕΔଆ class Foo { operator fun getValue(thisRef: Any?, property: KProperty<*>):
String { return "get value through delegation" } operator fun setValue(thisRef: Any?, property: KProperty<*>, value: String) { Log.d(TAG, "set value $value through delegation") } }

ҕৡ͞ΕΔଆ class Foo { operator fun getValue(thisRef: Any?, property: KProperty<*>):
String { return "get value through delegation" } operator fun setValue(thisRef: Any?, property: KProperty<*>, value: String) { Log.d(TAG, “set value $value through delegation") } } HFU7BMVF TFU7BMVF PQFSBUPSΛ࣮૷

ҕৡ͞ΕΔଆ class Foo : ReadWriteProperty<Any?, String> { override fun getValue(thisRef:
Any?, property: KProperty<*>): String { return "get value through delegation" } override fun setValue(thisRef: Any?, property: KProperty<*>, value: String) { Log.d(TAG, "set value $value through delegation") } } ΠϯλʔϑΣʔεΛ ࣮૷͢Δͱগָ͠

HFUUFSTFUUFSͷ ΧελϚΠζͱԿ͕ҧ͏ͷʁ

%FMFHBUFEQSPQFSUZ class Foo { operator fun getValue(thisRef: Any?, property: KProperty<*>):
String { return "get value through delegation" } operator fun setValue(thisRef: Any?, property: KProperty<*>, value: String) { Log.d(TAG, “set value $value through delegation") } }

HFUUFSTFUUFS var foo: String get() = "get value through getter"
set(value) { Log.d(TAG, "set value $value through delegation") }

HFUUFSTFUUFS ࣮૷ͷ΄͏͕ѹ౗తʹ؆୯

%FMFHBUFE1SPQFSUZΛ ࢖͏΂͖৔໘

w ڞ௨ԽͰ͖Δॲཧ w ෳࡶͳঢ়ଶΛอ͍࣋ͨ͠ w ෳࡶͳॲཧΛ͍ͨ͠ w ΍Γա͗஫ҙ %FMFHBUF1SPQFSUZΛ࢖͏΂͖৔໘

ڞ௨Խͯ͠੾Γग़ͯ͠ ҕৡݩ΍ϓϩύςΟͷ৘ใ͕ Θ͔Βͳ͘ͳΒͳ͍ʁ

w ҕৡݩΫϥεͷऔಘɾ੍ݶ w ϓϩύςΟͷϝλσʔλࢀর %FMFHBUF1SPQFSUZͰͰ͖Δ͜ͱ

ϓϩύςΟͷϝλσʔλ class Foo { operator fun getValue(thisRef: Any?, property: KProperty<*>):
String { return "get value through delegation" } operator fun setValue(thisRef: Any?, property: KProperty<*>, value: String) { Log.d(TAG, "set value $value through delegation") } } ҕৡݩͷϓϩύςΟ͕ଐ͢ΔΫϥε ܕͰ੍ݶ͢Δ͜ͱ΋Մೳ

ϓϩύςΟͷϝλσʔλ class Foo { operator fun getValue(thisRef: Any?, property: KProperty<*>):
String { return "get value through delegation" } operator fun setValue(thisRef: Any?, property: KProperty<*>, value: String) { Log.d(TAG, "set value $value through delegation") } } ҕৡݩͷϓϩύςΟͷ ϝλσʔλΛࢀরՄೳ

ϓϩύςΟͷϝλσʔλ class Bar { … operator fun provideDelegate(thisRef: Any?, property:
KProperty<*>): ReadOnlyProperty<Any?, T> { return this } } ,PUMJO͔Β͸ ҕৡΛఏڙͨ͠ λΠϛϯάͰݺ͹ΕΔ PQFSBUPS͕௥Ճ͞Εͨ

ϓϩύςΟͷϝλσʔλ class Sample { var bar: String by Bar() }
ΫϥεͷΠϯελϯεΛ ੜ੒ͨ͠ஈ֊ͰϓϩύςΟͷ৘ใΛ ಘΒΕΔΑ͏ʹͳͬͨ

w HFUUFSTFUUFSͷΧελϚΠζͰ  े෼ͳ৔໘͕ଟ͍ w ඪ४ϥΠϒϥϦ΍αʔυύʔςΟͷ  ϥΠϒϥϦΛ༗ޮ׆༻͢Δ %FMFHBUFE1SPQFSUZΛ࣮૷͢Δ͔

"OESPJEͰ %FMFHBUFE1SPQFSUZ

ඪ४ϥΠϒϥϦ

w ϓϩύςΟʹॳΊͯΞΫηεͨ࣌͠ʹ ϒϩοΫͷ಺༰Λ࣮ߦ w ࠷ऴߦͷ஋͕ճ໨Ҏ߱ͷ  ΞΫηεͰ͸࢖ΘΕΔ MB[Z

w "OESPJEʹ͸ίϯετϥΫλͰ  ॳظԽͰ͖ͳ͍΋ͷ͕ଟ͍ w FY "DUJWJUZͷPO$SFBUFҎ߱ʹΞ ΫηεՄೳͳ΋ͷ w *OUFOU w
γεςϜαʔϏε w FUDʜ MB[Z

MB[Z var param: String? = null override fun onCreate(savedInstanceState: Bundle?)
{ super.onCreate(savedInstanceState) param = intent.getStringExtra("param") Log.d(TAG, param) } ,PUMJOͷϓϩύςΟ͸ ॳظ஋͕ඞཁ

lateinit var param: String override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState)
param = intent.getStringExtra("param") Log.d(TAG, param) } MB[Z MBUFJOJUͰॳظ஋ෆཁʹͰ͖Δ

lateinit var param: String override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState)
param = intent.getStringExtra("param") Log.d(TAG, param) } MB[Z Ͱ΋Ұ౓୅ೖͨ͠Βมߋ͢Δඞཁ͕ ͳ͍ͷʹWBSʹ͢Δͷ͸ؾ࣋ͪѱ͍ʜ

val param: String by lazy { intent.getStringExtra("param") } override fun
onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) Log.d(TAG, param) } MB[Z Πϯελϯεੜ੒࣌ʹ͸࣮ߦ͞Εͳ͍ WBMͰએݴ

val param: String by lazy { intent.getStringExtra("param") } override fun
onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) Log.d(TAG, param) } MB[Z ࠷ॳʹΞΫηεͨ࣌͠ʹॳΊͯॳظԽ

w ϥΠϑαΠΫϧʹ஫ҙ͕ඞཁ w ಛʹ'SBHNFOU MB[Z

PCTFSWBCMFWFUPBCMF

w ϓϩύςΟͷมߋΛݕ஌ w WFUPBCMFͰ͸มߋΛड͚ೖΕΔ͔  ൑ఆ͢Δ͜ͱ͕Ͱ͖Δ PCTFSWBCMFWFUPBCMF

w XBZ%BUB#JOEJOHͱ  ૬ੑ͕ྑͦ͞͏ PCTFSWBCMFWFUPBCMF

w &EJU5FYUʹԿ͔ೖྗ͞Ε͍ͯͨΒ  ૹ৴ϘλϯΛ༗ޮʹ͢Δ PCTFSWBCMFWFUPBCMF

PCTFSWBCMFWFUPBCMF class ViewModel { var inputText: String by Delegates.observable("") {
property, oldValue, newValue -> buttonEnabled.set(newValue.isNotEmpty()) } var buttonEnabled = ObservableBoolean(false) } ςΩετ͕ۭͰͳ͚Ε͹ϘλϯΛ༗ޮʹ͢Δ %FMFHBUFE1SPQFSUZͷػೳ

PCTFSWBCMFWFUPBCMF class ViewModel { var inputText: String by Delegates.observable("") {
property, oldValue, newValue -> buttonEnabled.set(newValue.isNotEmpty()) } val buttonEnabled = ObservableBoolean(false) } Ϙλϯͷ༗ޮແޮΛ%BUB#JOEJOHʹ௨஌͢Δ %BUB#JOEJOHͷػೳ

PCTFSWBCMFWFUPBCMF <layout> <data> <variable name="viewModel" type="com.example.ViewModel"/> </data> <LinearLayout android:orientation="vertical"> <EditText
android:hint="Please input some text" android:text="@={viewModel.inputText}" /> <Button android:enabled="@{viewModel.buttonEnabled}" android:text="Send" /> </LinearLayout> </layout>

PCTFSWBCMFWFUPBCMF class MainActivity : AppCompatActivity() { val binding by lazy
{ DataBindingUtil.setContentView<ActivityMainBinding>( this@MainActivity, R.layout.activity_main) } override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) binding.viewModel = ViewModel() } }

PCTFSWBCMFWFUPBCMF

αʔυύʔςΟ ϥΠϒϥϦ

,PUUFS,OJGF IUUQTHJUIVCDPN+BLF8IBSUPOLPUUFSLOJGF

w #VUUFS,OJGFͷ+BLFۘ੡ w #VUUFS,OJGFͷ,PUMJOόʔδϣϯ ,PUUFS,OJGF

,PUUFS,OJGF val firstName: TextView by bindView(R.id.first_name) val lastName: TextView by
bindView(R.id.last_name) // Optional binding. val details: TextView? by bindOptionalView(R.id.details)

w ࣮૷͸#VUUFS,OJGFLUͷ  ϑΝΠϧͷΈ w ࣗ࡞%FMFHBUFE1SPQFSUZͷ  ࠷ॳͷษڧʹͪΐ͏ͲΑ͍ w 'SBHNFOUͰ࢖͏ͱ͖͸஫ҙ͕ඞཁ w %BUB#JOEJOH࢖͍ͬͯΕ͹ 
΋͏ඞཁ͸ͳ͍ʜ ,PUUFS,OJGF

,PUQSFG IUUQTHJUIVCDPNDIJCBUDIJOH,PUQSFG

w 4IBSFE1SFGFSFODFͷѻ͍Λ؆୯ʹ ͢ΔͨΊͷϥΠϒϥϦ w ࢲ͕࡞Γ·ͨ͠# ,PUQSFG

,PUQSFG object UserInfo : KotprefModel() { var name by stringPref()
var age by intPref(default = 14) } fun save(name: String, age: Int) { UserInfo.name = name UserInfo.age = age } fun show() { nameTextView.text = UserInfo.name ageTextView.text = UserInfo.age } 1SFGFSFODFͷΩʔ͸ ࢦఆෆཁ

,PUQSFG UserInfo.xml <?xml version='1.0' encoding='utf-8' standalone='yes' ?> <map> <string name="name">chibatching</string>
<int name="age" value="31" /> </map> ϓϩύςΟ໊ΛΩʔʹͯ͠อଘ Ϋϥε໊ͷ9.-Λੜ੒

w ϓϩύςΟ໊͕Ωʔ஋ʹͳΔ w Ωʔ஋ͷ؅ཧΛTUSJOHϦιʔε΍ఆ ਺ΫϥεͰ͠ͳ͍͍͘ ,PUQSFG

w ,PEFJO w %*ϥΠϒϥϦ w SFNPUFLPOpH w 'JSFCBTF3FNPUF$POpHͷσʔλΞΫηε ΄͔ʹ΋ʜ IUUQTHJUIVCDPN4BMPNPO#SZT,PEFJO
IUUQTHJUIVCDPNDIJCBUDIJOHSFNPUFLPOpH

w %FMFHBUFE1SPQFSUZ͸ෳࡶͳ  ϓϩύςΟͷΞΫηεॲཧΛ  ࣮ݱͰ͖Δ w ैདྷͳΒ"OOPUBUJPO1SPDFTTPSͰ΍ͬͯ ͍ͨΑ͏ͳ͜ͱ΋৔߹ʹΑͬͯ͸Մೳ w HFUUFSTFUUFSͷΧελϚΠζ΍  ϥΠϒϥϦͷ׆༻ͱ߹Θͤͯݕ౼
·ͱΊ

Delegated propertyで Android開発をもっと便利に @ Gunosy B...

Delegated propertyで Android開発をもっと便利に @ Gunosy Beer Bash #12

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