{"id":2605,"date":"2024-10-08T21:23:28","date_gmt":"2024-10-08T12:23:28","guid":{"rendered":"http:\/\/batmask.dothome.co.kr\/?p=2605"},"modified":"2024-10-08T21:23:28","modified_gmt":"2024-10-08T12:23:28","slug":"kotlin-%ec%97%90-%ec%9d%b5%ec%88%99%ed%95%b4%ec%a7%80%ea%b8%b0-%eb%82%af%ec%84%a0-%eb%ac%b8%eb%b2%95%eb%93%a4-%ec%a0%95%eb%a6%ac-4","status":"publish","type":"post","link":"http:\/\/batmask.net\/index.php\/2024\/10\/08\/2605\/","title":{"rendered":"Kotlin \uc5d0 \uc775\uc219\ud574\uc9c0\uae30 : \ub0af\uc120 \ubb38\ubc95\ub4e4 \uc815\ub9ac #4"},"content":{"rendered":"\n

codepro \ub54c\ubb38\uc5d0 \ud3ec\uc2a4\ud305\uc744 \ub098\ub220\uc11c \uacc4\uc18d \uc9e4\ub77c\uba39\uc5b4\uc57c \ud558\ub294\uac8c \uc9dc\uc99d\ub098\ub124.<\/p>\n\n\n\n

delegation :
https:\/\/kotlinlang.org\/docs\/delegation.html<\/a>
https:\/\/kotlinlang.org\/docs\/delegated-properties.html<\/a><\/h3>\n\n\n\n

\uc704\uc784(delegation) \ub514\uc790\uc778 \ud328\ud134( https:\/\/en.wikipedia.org\/wiki\/Delegation_pattern<\/a> )\uc740 \ud55c \ud074\ub798\uc2a4\uc758 \uba64\ubc84 \uad6c\ud604\uc744 \uc9c1\uc811 \ud558\uc9c0 \uc54a\uace0, \ub2e4\ub978 \ud074\ub798\uc2a4\uc758 \uba64\ubc84\uad6c\ud604\uc744 \uc774\uc6a9\ud558\ub294 \uac83\uc774\ub2e4. \ub2e4\uc2dc\ub9d0\ud558\uba74, \ub2e4\ub978 \ud074\ub798\uc2a4\uc5d0\uac8c \uc704\uc784\ud558\ub294 \uac83\uc774\ub2e4. \ucf54\ud2c0\ub9b0\uc740 \uc774\ub97c \uc5b8\uc5b4 \uc218\uc900\uc5d0\uc11c \uc9c1\uc811\uc801\uc73c\ub85c \uc9c0\uc6d0\ud55c\ub2e4. \ubc14\ub85c ‘by’\ud0a4\uc6cc\ub4dc\uac00 \uadf8\uac83\uc774\ub2e4.<\/p>\n\n\n\n

<\/circle><\/circle><\/circle><\/g><\/svg><\/span><\/path><\/path><\/svg><\/span>
interface<\/span> <\/span>ClosedShape<\/span> {<\/span><\/span>\n    <\/span>fun<\/span> <\/span>area<\/span>(): <\/span>Int<\/span><\/span>\n}<\/span><\/span>\n<\/span>\nclass<\/span> <\/span>Rectangle<\/span>(<\/span>val<\/span> width: <\/span>Int<\/span>, <\/span>val<\/span> height: <\/span>Int<\/span>) : <\/span>ClosedShape<\/span> {<\/span><\/span>\n    <\/span>override<\/span> <\/span>fun<\/span> <\/span>area<\/span>() <\/span>=<\/span> width <\/span>*<\/span> height<\/span><\/span>\n}<\/span><\/span>\n<\/span>\n\/\/ The ClosedShape implementation of Window delegates to that of the Rectangle that is bounds<\/span><\/span>\nclass<\/span> <\/span>Window<\/span>(<\/span>private<\/span> <\/span>val<\/span> bounds: <\/span>Rectangle<\/span>) : <\/span>ClosedShape<\/span> <\/span>by<\/span> <\/span>bounds<\/span><\/span><\/code><\/pre><\/div>\n\n\n\n
\uc704 \ucf54\ub4dc\uc5d0\uc11c Window \ud074\ub798\uc2a4\ub294 ClosedShape \uc778\ud130\ud398\uc774\uc2a4\uc758 \uad6c\ud604\uc744 bounds\uc5d0\uac8c \uc704\uc784\ud558\uace0 \uc788\ub2e4. <\/p>\n\n\n\n
\ud074\ub798\uc2a4 \ub2e8\uc704\uac00 \uc544\ub2c8\ub77c property\uc5d0\uc11c\ub3c4 \uac00\ub2a5\ud55c\ub370, \ub9e4\uc6b0 \ud754\ud788 \ubcfc \uc218 \uc788\ub2e4. \uc774 \ub54c, get()\/set() \uc774 \uc704\uc784\ub418\ub294 \ub300\uc0c1\uc758 getValue(), setValue()\ub97c \ub300\uc2e0 \ubd80\ub974\uac8c \ub418\ubbc0\ub85c \uc774\ub4e4\uc774 \uad6c\ud604\ub418\uc5b4 \uc788\uc5b4\uc57c \ud55c\ub2e4.<\/p>\n\n\n\n
<\/circle><\/circle><\/circle><\/g><\/svg><\/span><\/path><\/path><\/svg><\/span>
class<\/span> <\/span>Delegate<\/span> {<\/span><\/span>\n    <\/span>operator<\/span> <\/span>fun<\/span> <\/span>getValue<\/span>(thisRef: <\/span>Any<\/span>?, property: <\/span>KProperty<\/span><*>): <\/span>String<\/span> {<\/span><\/span>\n        <\/span>return<\/span> <\/span>"<\/span>$thisRef<\/span>, thank you for delegating '${property.name}' to me!"<\/span><\/span>\n    }<\/span><\/span>\n<\/span>\n    <\/span>operator<\/span> <\/span>fun<\/span> <\/span>setValue<\/span>(thisRef: <\/span>Any<\/span>?, property: <\/span>KProperty<\/span><*>, <\/span>value<\/span>: <\/span>String<\/span>) {<\/span><\/span>\n        <\/span>println<\/span>(<\/span>"<\/span>$value<\/span> has been assigned to '${property.name}' in <\/span>$thisRef<\/span>."<\/span>)<\/span><\/span>\n    }<\/span><\/span>\n}<\/span><\/span>\n<\/span>\nclass<\/span> <\/span>Example<\/span> {<\/span><\/span>\n    <\/span>var<\/span> p: <\/span>String<\/span> <\/span>by<\/span> <\/span>Delegate<\/span>() <\/span>\/\/ val\/var <property name>: <Type> by <expression><\/span><\/span>\n}<\/span><\/span>\n<\/span><\/code><\/pre><\/div>\n\n\n\n
\"seperator\"<\/figure>\n\n\n\n
Lazy initialization<\/h3>\n\n\n\n
 \uc55e\uc5d0\uc11c delegated property \ub97c\ub2e4\ub918\ub294\ub370, \ucf54\ud2c0\ub9b0 \ud45c\uc900 \ub77c\uc774\ube0c\ub7ec\ub9ac\uc5d0\uc11c \uc9c0\uc6d0\ud574\uc8fc\ub294 \uac83\ub4e4\uc774 \uc788\ub2e4. \uadf8 \uc911 \ud558\ub098\uac00 Lazy\uc774\ub2e4. <\/p>\n\n\n\n
<\/circle><\/circle><\/circle><\/g><\/svg><\/span><\/path><\/path><\/svg><\/span>
val<\/span> lazyValue: <\/span>String<\/span> <\/span>by<\/span> <\/span>lazy<\/span> {<\/span><\/span>\n    <\/span>println<\/span>(<\/span>"computed!"<\/span>)<\/span><\/span>\n    <\/span>"Hello"<\/span><\/span>\n}<\/span><\/span>\n<\/span>\nfun<\/span> <\/span>main<\/span>() {<\/span><\/span>\n    <\/span>println<\/span>(lazyValue)<\/span><\/span>\n    <\/span>println<\/span>(lazyValue)<\/span><\/span>\n}<\/span><\/span><\/code><\/pre><\/div>\n\n\n\n
\uc774\ub294 \uc9c0\uc5f0\ub41c \ucd08\uae30\ud654\uc5d0 \uc0ac\uc6a9\ub418\ub294\ub370, lambda \ud568\uc218\ub97c \uc778\uc790\ub85c \ubc1b\uae30 \ub54c\ubb38\uc5d0, \uc5ec\uae30\uc11c \ucd08\uae30\ud654 \ucf54\ub4dc\ub97c \uc804\ub2ec\ud574\uc8fc\uba74 \ub41c\ub2e4. \ucc98\uc74c property\uac00 \ubd88\ub9ac\uba74 get()\uc774 \uc2e4\ud589\ub418\uc5b4 \ub118\uaca8\uc900 \ub78c\ub2e4 \ud568\uc218\uac00 \uc2e4\ud589\ub418\uace0 \uadf8 \uacb0\uacfc\ub97c \uae30\uc5b5\ud574\ub454\ub2e4. \uadf8 \ub2e4\uc74c\ubd80\ud130\ub294 \uae30\uc5b5\ub41c \uacb0\uacfc\uac12\ub9cc \ub3cc\ub824\uc8fc\uac8c \ub41c\ub2e4.<\/p>\n\n\n\n
\"seperator\"<\/figure>\n\n\n\n
scope functions <\/h3>\n\n\n\n
\uc2a4\ucf54\ud504 \ud568\uc218\ub4e4\uc740 let, run, with, apply, also \uc758 \ub2e4\uc12f\uac00\uc9c0\uac00 \uc788\ub2e4. \uc0ac\uc6a9\uc5d0 \ud63c\ub3d9\uc774 \uc62c \uc218 \uc788\ub294\ub370, \uc815\ub9ac\ub0b4\uc6a9\uc774 \uc880 \ub9ce\uc73c\ubbc0\ub85c, \uae30\uc874 \ud3ec\uc2a4\ud305\uc73c\ub85c \ub300\uccb4\ud55c\ub2e4. <\/p>\n\n\n\n
http:\/\/batmask.dothome.co.kr\/index.php\/2021\/12\/10\/286\/<\/a><\/p>\n\n\n\n
\"seperator\"<\/figure>\n\n\n\n
coroutine : https:\/\/kotlinlang.org\/docs\/coroutines-overview.html<\/a><\/h3>\n\n\n\n
\ucf54\ud2c0\ub9b0\uc758 \ud575\uc2ec \ub0b4\uc6a9\uc911 \ud558\ub098\uc774\uc9c0\ub9cc, \uc774\uac83\ub3c4 \ub0b4\uc6a9\uc774 \ub9ce\ub2e4. \uae30\uc874\uc5d0 \uc791\uc131\ud588\ub358 \ubcc4\ub3c4 \ud3ec\uc2a4\ud305 \ucc38\uace0. <\/p>\n\n\n\n
Kotlin: Coroutines <\/a><\/p>\n\n\n\n
\"seperator\"<\/figure>\n\n\n\n
Flow : https:\/\/kotlinlang.org\/docs\/flow.html<\/a><\/h3>\n\n\n\n
\ucf54\ub8e8\ud2f4\uacfc \ud568\uaed8 \ubd10\uc57c\ud560 \uc5ed\uc2dc \ud575\uc2ec\ub0b4\uc6a9. \uc774\uac83\ub3c4 \ub0b4\uc6a9\uc774 \ub9ce\uc73c\ub2c8 \uae30\uc874 \uc791\uc131\ud588\ub358 \ud3ec\uc2a4\ud305 \ucc38\uace0.<\/p>\n\n\n\n
Kotlin : Flow Part. 1 <\/a><\/p>\n\n\n\n
Kotlin : Flow Part.2 (Shared Flow, State Flow) <\/a><\/p>\n\n\n\n
\"seperator\"<\/figure>\n\n\n\n
annotation : https:\/\/kotlinlang.org\/docs\/annotations.html<\/a><\/h3>\n\n\n\n
annotation\uc740 \ucf54\ub4dc\uc5d0 \uba54\ud0c0 \ub370\uc774\ud130\ub97c \ubd99\uc774\ub294\uac78 \uc758\ubbf8\ud55c\ub2e4. \ucc98\uc74c\uc5d4 \uac04\ub2e8\ud55c \uc5d0\ub7ec\ub098 \uacbd\uace0\ud45c\uc2dc \uc548\ud558\uac8c \ub9cc\ub4dc\ub294 \uc815\ub3c4\uc758 \uc218\uc900\uc73c\ub85c \uc54c\uc558\uc5c8\ub294\ub370, \uc5b4\ub290\uc21c\uac04 \ud2b9\ud788 \ucf54\ud2c0\ub9b0\uc5d0\uc11c\ub294 compose\ub97c \uc4f0\ub824\uba74 \uaf2d \ud544\uc694\ud558\ub4ef\uc774 \ucf54\ub529\uc758 \ud55c \ubd80\ubd84\uc774 \ub418\ubc84\ub838\ub2e4. \uc608\uc804 \uc5b8\uc5b4\ub4e4\uc758 \ud504\ub9ac\ud504\ub85c\uc138\uc11c \uc791\uc5c5\ub4e4\uc774 \ubb38\uc81c\uac00 \ub9ce\uc544 \uc0ac\ub77c\uc84c\uc9c0\ub9cc, \uacb0\uad6d \uc774\uac83\ub4e4\uc774 annotation\uc73c\ub85c \uc7ac\ud0c4\uc0dd\ud55c \ub290\ub08c\ub3c4 \ub4e0\ub2e4. \uc2e4\uc81c\ub85c annotation\uc740 \uba54\uc778 \ucf54\ub4dc\uc5d0 \uc601\ud5a5\uc744 \ubbf8\uce58\uc9c0 \uc54a\uac8c \ucef4\ud30c\uc77c\ub7ec\uc5d0 \uc758\ud574 \uc804\ucc98\ub9ac \ub41c\ub2e4. <\/p>\n\n\n\n
annotation\uc744 \ub9cc\ub4e4\ub824\uba74 \ud074\ub798\uc2a4 \uc55e\uc5d0 ‘annotation’\uc744 \ubd99\uc5ec\uc8fc\uba74 \ub41c\ub2e4.<\/p>\n\n\n\n
<\/circle><\/circle><\/circle><\/g><\/svg><\/span><\/path><\/path><\/svg><\/span>
annotation<\/span> <\/span>class<\/span> <\/span>Special<\/span><\/span>\n\/\/ usage <\/span><\/span>\n@Special<\/span> <\/span>class<\/span> <\/span>MyClass<\/span> { }<\/span><\/span>\n@Special<\/span> <\/span>fun<\/span> <\/span>myFunction<\/span>() { }<\/span><\/span><\/code><\/pre><\/div>\n\n\n\n
\ud30c\ub77c\ubbf8\ud130\ub97c \ubc1b\ub294 \uacbd\uc6b0, \ub2e4\uc74c\uacfc \uac19\ub2e4. \uadf8\ub0e5 \uc77c\ubc18 \ud074\ub798\uc2a4\uc640 \ud06c\uac8c \ub2e4\ub974\uc9c0 \uc54a\uac8c \ub290\uaef4\uc9c4\ub2e4.<\/p>\n\n\n\n
<\/circle><\/circle><\/circle><\/g><\/svg><\/span><\/path><\/path><\/svg><\/span>
annotation<\/span> <\/span>class<\/span> <\/span>Review<\/span>(<\/span>val<\/span> reviewer: <\/span>String<\/span>, <\/span>val<\/span> date: <\/span>String<\/span>)<\/span><\/span>\n@Review<\/span>(reviewer <\/span>=<\/span> <\/span>"John Doe"<\/span>, date <\/span>=<\/span> <\/span>"2022-01-01"<\/span>)<\/span><\/span>\nclass<\/span> <\/span>Document<\/span> { }<\/span><\/span><\/code><\/pre><\/div>\n\n\n\n
\uae30\ubcf8\uc801\uc73c\ub85c \ube4c\ud2b8\uc778 annotation\ub4e4\uc774 \uc874\uc7ac\ud55c\ub2e4. @deprecated, @JvmOverloads, @JvmStatic, @Suppress, @Retention, @Target, @Repeatable \ub4f1. custom annotation\uc5d0 \ub300\ud574\uc120 \uc0ac\uc2e4, \ubcc4\uac1c\uc758 \ud3ec\uc2a4\ud305\uc73c\ub85c \uc815\ub9ac\ud558\ub294\uac8c \ub9de\ub294 \ub0b4\uc6a9\uac19\uace0, \uc544\ub798 \ucc38\uc870\uae00\ub85c \ub0b4\uc6a9\uc744 \ub300\uccb4\ud55c\ub2e4. <\/p>\n\n\n\n
\"seperator\"<\/figure>\n\n\n\n
Generics, in, out : https:\/\/kotlinlang.org\/docs\/generics.html<\/a><\/h3>\n\n\n\n
Generics\uac00 \uc0ac\uc6a9\ub41c\uac74 \uc624\uc624\uc624\uc624\ub798\uc804 C++\uc758 STL(Standard Template Library)\ub4f1 Template \uc0ac\uc6a9\uae30\uc5b5\uc774 \uc788\uae30 \ub54c\ubb38\uc5d0 \uc774\uac8c \ubb54\uc9c0 \uc790\uc138\ud55c \uc124\uba85\uc740 \uc0dd\ub7b5. generic\uc740 function, class, interface\uc5d0 \uc0ac\uc6a9\uc774 \uac00\ub2a5\ud558\ub2e4. \ud568\uc218\uc5d0\uc11c\uc758 \uc120\uc5b8 \ubc29\ubc95\uc740 \ub2e4\uc74c\uacfc \uac19\ub2e4.<\/p>\n\n\n\n
<\/circle><\/circle><\/circle><\/g><\/svg><\/span><\/path><\/path><\/svg><\/span>
fun<\/span> <<\/span>T<\/span>> <\/span>singletonList<\/span>(item: <\/span>T<\/span>): <\/span>List<\/span><<\/span>T<\/span>> {<\/span><\/span>\n}<\/span><\/span>\n<\/span>\nfun<\/span> <<\/span>T<\/span>> <\/span>T<\/span>.<\/span>basicToString<\/span>(): <\/span>String<\/span> { <\/span>\/\/ extension function<\/span><\/span>\n}<\/span><\/span>\nval<\/span> l <\/span>=<\/span> <\/span>singletonList<\/span><<\/span>Int<\/span>>(<\/span>1<\/span>)<\/span><\/span><\/code><\/pre><\/div>\n\n\n\n
\ud568\uc218 \uc774\ub984\uc804\uc5d0 <T>\ub85c \uc368\uc8fc\uba70, \uaf2d T\uac00 \uc544\ub2c8\uc5b4\ub3c4 \ub41c\ub2e4. \uc5ec\ub7ec\uac1c\uc778 \uacbd\uc6b0, <T, F> \uc640 \uac19\uc774 \uc368\uc904 \uc218 \uc788\ub2e4. \uc5ec\uae30\uc11c T, F\ub97c \ud0c0\uc785 \ud30c\ub77c\ubbf8\ud130\ub77c\uace0 \ud55c\ub2e4. \uadf8\ub9ac\uace0 \uc0ac\uc6a9\uc2dc\uc5d0 \uc774\ub984\ub4a4\uc5d0 <>\uad04\ud638\uc640 \ud568\uaed8 \uc6d0\ud558\ub294 \ud0c0\uc785\uc744 \ub123\uc5b4\uc8fc\uba74 \ub41c\ub2e4. \uc774 \ud0c0\uc785\uc774 \uc120\uc5b8\uc5d0 \uc0ac\uc6a9\ub41c \ud0c0\uc785 \ud30c\ub77c\ubbf8\ud130 \uc790\ub9ac\ub97c \ub300\uce58\ud55c\ub2e4. <\/p>\n\n\n\n
\ud074\ub798\uc2a4\uc758 \uacbd\uc6b0\ub294 \ub2e4\uc74c\uacfc \uac19\uc774 \uc0ac\uc6a9\ud55c\ub2e4.<\/p>\n\n\n\n
<\/circle><\/circle><\/circle><\/g><\/svg><\/span><\/path><\/path><\/svg><\/span>
class<\/span> <\/span>Box<\/span><<\/span>T<\/span>>(t: <\/span>T<\/span>) {<\/span><\/span>\n    <\/span>var<\/span> <\/span>value<\/span> <\/span>=<\/span> t<\/span><\/span>\n}<\/span><\/span>\nval<\/span> box: <\/span>Box<\/span><<\/span>Int<\/span>> <\/span>=<\/span> <\/span>Box<\/span><<\/span>Int<\/span>>(<\/span>1<\/span>)<\/span><\/span><\/code><\/pre><\/div>\n\n\n\n
\uc790\ubc14\uc640 \uac19\uc774, \ud074\ub798\uc2a4 \uc774\ub984\ub4a4\uc5d0 <T> \uc640 \uac19\uc774 \ucd94\uac00\ud574\uc900\ub2e4. \uc774 \ud6c4, \ud0c0\uc785\uc774 \ub4e4\uc5b4\uac08 \uc790\ub9ac\uc5d0 \uc774 T\ub97c \uc0ac\uc6a9\ud558\uac8c\ub41c\ub2e4. \uc0ac\uc6a9\uc2dc\uc5d0\ub294 \ud568\uc218 \ub54c\uc640 \ub3d9\uc77c\ud558\uac8c, \ud074\ub798\uc2a4 \uc774\ub984\ub4a4\uc5d0 <\ud0c0\uc785>\uacfc \uac19\uc774 \uc0ac\uc6a9\ud55c\ub2e4. \uc778\ud130\ud398\uc774\uc2a4\ub3c4 \ud074\ub798\uc2a4\uc640 \ub3d9\uc77c\ud558\uac8c \uc0ac\uc6a9\ud55c\ub2e4.<\/p>\n\n\n\n
\uc774\uc81c in, out  \ud0a4\uc6cc\ub4dc\uc5d0 \ub300\ud574 \uc54c\uc544\ubcf4\uc790. <\/p>\n\n\n\n
\uc790\ubc14\ub791 \ucc28\uc774\uc810\uc744 \uc54c\uc544\uc57c \ud574\uc11c \uc77c\ub2e8 \uc790\ubc14\uc758 generic\uc5d0 \ub300\ud574 \uc880 \uc54c\uc544\uc57c \ud55c\ub2e4. \uc790\ubc14\uc5d0\uc11c generic type\uc740 \ubd88\ubcc0(invariant)\uc774\ub2e4. \ubb34\uc2a8 \ub9d0\uc774\ub0d0\uba74, <\/p>\n\n\n\n
<\/circle><\/circle><\/circle><\/g><\/svg><\/span><\/path><\/path><\/svg><\/span>
\/\/ Java<\/span><\/span>\nList<\/span><<\/span>String<\/span>> <\/span>strs<\/span> <\/span>=<\/span> <\/span>new<\/span> ArrayList<<\/span>String<\/span>>();<\/span><\/span>\n<\/span>\n\/\/ Java reports a type mismatch here at compile-time.<\/span><\/span>\nList<\/span><<\/span>Object<\/span>> <\/span>objs<\/span> <\/span>=<\/span> strs;<\/span><\/span><\/code><\/pre><\/div>\n\n\n\n
\uc704\uc640 \uac19\uc774 List<String>\uacfc List<Object>\ub294 \ud638\ud658\uc774 \ub418\uc9c0 \uc54a\ub294\ub2e4. \uc8fc\uc5b4\uc9c4 generic type\ub9cc \uc0ac\uc6a9\uc774 \uac00\ub2a5\ud558\ub2e4. \uc774\uac74 \ub7f0\ud0c0\uc784\uc2dc \uc548\uc804\uc744 \uc704\ud55c \uac83\uc774\ub77c\uace0 \ud55c\ub2e4. \ud558\uc9c0\ub9cc, \uc774\ub7f0\uacbd\uc6b0\uac00 \ud544\uc694\ud558\uc9c0 \uc54a\ub098? \ub2e4\uc74c \uc2a4\ud0dd\uc758 \uc608\ub97c \ubcf4\uc790.<\/p>\n\n\n\n
<\/circle><\/circle><\/circle><\/g><\/svg><\/span><\/path><\/path><\/svg><\/span>
\/\/java<\/span><\/span>\npublic<\/span> <\/span>void<\/span> <\/span>pushAll<\/span>(Iterable<\/span><<\/span>E<\/span>><\/span> src) {<\/span><\/span>\n    <\/span>for<\/span> (E<\/span> <\/span>e<\/span> <\/span>:<\/span> src)<\/span><\/span>\n        <\/span>push<\/span>(e);<\/span><\/span>\n<\/span>\n...<\/span><\/span>\nStack<\/span><<\/span>Number<\/span>> <\/span>numberStack<\/span> <\/span>=<\/span> <\/span>new<\/span> Stack<<\/span>Number<\/span>>();<\/span><\/span>\nIterable<\/span><<\/span>Integer<\/span>> <\/span>integers<\/span> <\/span>=<\/span> ...;<\/span><\/span>\n\/\/ Error!<\/span><\/span>\nnumberStack.<\/span>pushAll<\/span> (integers);<\/span><\/span><\/code><\/pre><\/div>\n\n\n\n
 \uc704\uc640 \uac19\uc774 \uc0ac\uc6a9\ud558\uba74, invariant\ud55c \uc131\uc9c8 \ub54c\ubb38\uc5d0 Stack<Number>\uc5d0 Integer\ub97c \ub123\uc744 \uc218 \uc5c6\uc5b4\uc11c \uc5d0\ub7ec\uac00 \ubc1c\uc0dd\ud55c\ub2e4. \uc774 \ub54c \uc790\ubc14\uc5d0\uc11c \uc0ac\uc6a9\ud558\ub294\uac8c wildcard type \uc778\uc790\ub85c < ?  extends E > \uc640 \uac19\uc774 \uc0ac\uc6a9\ud55c\ub2e4.<\/p>\n\n\n\n
<\/circle><\/circle><\/circle><\/g><\/svg><\/span><\/path><\/path><\/svg><\/span>
\/\/ Java<\/span><\/span>\npublic<\/span> <\/span>void<\/span> <\/span>pushAll<\/span>(Iterable<\/span><?<\/span> extends E<\/span>><\/span> src) {<\/span><\/span>\n    <\/span>for<\/span> (E<\/span> <\/span>e<\/span> <\/span>:<\/span> src)<\/span><\/span>\n        <\/span>push<\/span>(e);<\/span><\/span>\n<\/span><\/code><\/pre><\/div>\n\n\n\n
\uc774 \uac83\uc758 \uc758\ubbf8\ub294 E \ud0c0\uc785\uacfc E\uc758 \uc11c\ube0c\ud0c0\uc785\uc744 \ub2e4 \ubc1b\uc744 \uc218 \uc788\ub2e4\ub294 \uc598\uae30\ub85c \uc704\uc758 \ubb38\uc81c\uac00 \ud574\uacb0\ub41c\ub2e4. \uc774\ub807\uac8c wildcard\uc640 extends-bound\ub97c \uc8fc\uac8c\ub418\uba74 \uc774 \ud0c0\uc785\uc740 covariant\uac00 \ub41c\ub2e4. \uadf8\ub7fc \ub2e4\uc74c\uc73c\ub85c popAll()\uc744 \uc0dd\uac01\ud574\ubcf4\uc790.<\/p>\n\n\n\n
<\/circle><\/circle><\/circle><\/g><\/svg><\/span><\/path><\/path><\/svg><\/span>
\/\/java<\/span><\/span>\npublic<\/span> <\/span>void<\/span> <\/span>popAll<\/span>(Collection<\/span><<\/span>E<\/span>><\/span> dest) {<\/span><\/span>\n    <\/span>while<\/span>(<\/span>!<\/span>isEmpty<\/span>())<\/span><\/span>\n        dest.<\/span>add<\/span>(<\/span>pop<\/span>());<\/span><\/span>\n}<\/span><\/span>\n...<\/span><\/span>\nStack<\/span><<\/span>Number<\/span>> <\/span>numberStack<\/span> <\/span>=<\/span> <\/span>new<\/span> Stack<<\/span>Number<\/span>>();<\/span><\/span>\nCollection<\/span><<\/span>Object<\/span>> <\/span>objects<\/span> <\/span>=<\/span> ...;<\/span><\/span>\nnumberStack.<\/span>popAll<\/span>(objects);  <\/span>\/\/ Error!!<\/span><\/span>\n-<\/span> <\/span>-<\/span> <\/span>-<\/span> <\/span><\/span>\npublic<\/span> <\/span>void<\/span> <\/span>popAll<\/span>(Collection<\/span><?<\/span> <\/span>super<\/span> E<\/span>><\/span> dest) {<\/span><\/span>\n<\/span><\/code><\/pre><\/div>\n\n\n\n
\uc774 \uacbd\uc6b0, Number\ub97c Collection<Object>\uc5d0 \ub123\uc744 \uc218 \uc5c6\uae30 \ub54c\ubb38\uc5d0 \ub610\ub2e4\uc2dc \uc5d0\ub7ec\uc5d0 \uc9c1\uba74\ud55c\ub2e4. \uc774 \ub54c\ub294 pushAll\uacfc \ubc18\ub300\uc758 \uacbd\uc6b0\ub85c, <? super E> wildcard type\uc744 \uc0ac\uc6a9\ud55c\ub2e4.<\/p>\n\n\n\n
\uc774 \uacbd\uc6b0\uc5d0\ub294 contravariance\ub77c\uace0 \ud55c\ub2e4. \uc5ec\uae30\uc11c \uc804\uc790\uc758 \uacbd\uc6b0, \uc778\uc2a4\ud134\uc2a4\ub97c \uc0dd\uc131\ud574\uc11c \uc2a4\ud0dd\uc5d0 \ub123\uae30 \ub54c\ubb38\uc5d0 \uc0dd\uc0b0\uc790(producer)\ub77c \uce6d\ud558\uace0, \ud6c4\uc790\uc758 \uacbd\uc6b0 \uaebc\ub0b4\uc640 \uc0ac\uc6a9\ud558\uae30 \ub54c\ubb38\uc5d0 \uc18c\ube44\uc790(consumer)\ub77c \uce6d\ud55c\ub2e4. \uadf8\ub798\uc11c \uc774\ub7f0\uacbd\uc6b0 PECS(Producer-Extends, Consumer-Super)\ub85c \uae30\uc5b5\ud558\uace0 \uc0ac\uc6a9\ud55c\ub2e4.<\/p>\n\n\n\n
\uadf8\ub7fc \uc774\uc81c PECS\uc5d0 \ud574\ub2f9\ud558\uc9c0 \uc54a\ub294 \uacbd\uc6b0\uc5d0 \ub300\ud574 \uc54c\uc544\ubcf4\uc790.<\/p>\n\n\n\n
<\/circle><\/circle><\/circle><\/g><\/svg><\/span><\/path><\/path><\/svg><\/span>
\/\/ Java<\/span><\/span>\ninterface<\/span> <\/span>Source<\/span><<\/span>T<\/span>> {<\/span><\/span>\n    T <\/span>nextT<\/span>();<\/span><\/span>\n}<\/span><\/span>\n<\/span>\n\/\/ Java<\/span><\/span>\nvoid<\/span> <\/span>demo<\/span>(Source<\/span><<\/span>String<\/span>><\/span> strs) {<\/span><\/span>\n    Source<\/span><<\/span>Object<\/span>> <\/span>objects<\/span> <\/span>=<\/span> strs; <\/span>\/\/ !!! Not allowed in Java<\/span><\/span>\n    <\/span>\/\/ ...<\/span><\/span>\n}<\/span><\/span><\/code><\/pre><\/div>\n\n\n\n
\uc774 \uacbd\uc6b0, consumer method\ub3c4 \uc5c6\uae30 \ub54c\ubb38\uc5d0 \uc644\uc804\ud788 \uc548\uc804\ud558\uace0 \ub9c9\uc744 \uc774\uc720\uac00 \uc5c6\ub2e4. \ud558\uc9c0\ub9cc, \uc774\ub97c \ud53c\ud558\uae30\uc704\ud574 Source<? extends Obejct>\ub97c \uc368\uc918\uc57c \ud55c\ub2e4.<\/p>\n\n\n\n
\ucf54\ud2c0\ub9b0\uc5d0\uc11c\ub294 \uc774\ub97c \ucef4\ud30c\uc77c\ub7ec\uc5d0\uac8c \uc54c\ub824\uc904 \ubc29\ubc95\uc774 \uc788\ub2e4. declaration-site variance \ub77c\ub294 \uac83\uc774\ub2e4.  \ud0c0\uc785 T\uac00 \uc624\uc9c1 \ub9ac\ud134\ub9cc\ub418\uace0(produced), consumed \ub418\ub294 \uc77c\uc774 \uc5c6\ub2e4\ub294 \uc758\ubbf8\ub85c ‘out’\uc744 \uc368\uc900\ub2e4.<\/p>\n\n\n\n
<\/circle><\/circle><\/circle><\/g><\/svg><\/span><\/path><\/path><\/svg><\/span>
interface<\/span> <\/span>Source<\/span><<\/span>out<\/span> <\/span>T<\/span>> {<\/span><\/span>\n    <\/span>fun<\/span> <\/span>nextT<\/span>(): <\/span>T<\/span><\/span>\n}<\/span><\/span>\n<\/span>\nfun<\/span> <\/span>demo<\/span>(strs: <\/span>Source<\/span><<\/span>String<\/span>>) {<\/span><\/span>\n    <\/span>val<\/span> objects: <\/span>Source<\/span><<\/span>Any<\/span>> <\/span>=<\/span> strs <\/span>\/\/ This is OK, since T is an out-parameter<\/span><\/span>\n}<\/span><\/span>\n<\/span>\ninterface<\/span> <\/span>Comparable<\/span><<\/span>in<\/span> <\/span>T<\/span>> {<\/span><\/span>\n    <\/span>operator<\/span> <\/span>fun<\/span> <\/span>compareTo<\/span>(other: <\/span>T<\/span>): <\/span>Int<\/span><\/span>\n}<\/span><\/span>\n<\/span>\nfun<\/span> <\/span>demo<\/span>(x: <\/span>Comparable<\/span><<\/span>Number<\/span>>) {<\/span><\/span>\n    x.<\/span>compareTo<\/span>(<\/span>1.0<\/span>) <\/span>\/\/ 1.0 has type Double, which is a subtype of Number<\/span><\/span>\n    <\/span>\/\/ Thus, you can assign x to a variable of type Comparable<Double><\/span><\/span>\n    <\/span>val<\/span> y: <\/span>Comparable<\/span><<\/span>Double<\/span>> <\/span>=<\/span> x <\/span>\/\/ OK!<\/span><\/span>\n}<\/span><\/span><\/code><\/pre><\/div>\n\n\n\n
\uc774\uc640 \ubc18\ub300\ub85c \uc624\uc9c1 \uc18c\ube44(consumed)\ub9cc \ub418\uace0 \uc0dd\uc0b0(produced)\uc740 \uc548\ub418\ub294 \uacbd\uc6b0\uc5d0, ‘in’ \ud0a4\uc6cc\ub4dc\ub97c \uc0ac\uc6a9\ud55c\ub2e4. Comparable\uc740 \ud6cc\ub96d\ud55c \uc608\uc774\ub2e4.<\/p>\n\n\n\n
\uc774 \uc678\uc5d0\ub3c4 type projection, star projection\ub4f1\uc774 \uc788\ub294\ub370 \ubb38\uc11c\ub97c \ucc38\uace0\ud558\uc2dc\uae38.  \uacf5\uc2dd \ubb38\uc11c ( https:\/\/kotlinlang.org\/docs\/generics.html<\/a> ) \ub098, \uae30\ud0c0 \ub2e4\ub978 \ubb38\uc11c( \uc608: https:\/\/kt.academy\/article\/kfde-generics<\/a> ) \ub4f1<\/p>\n","protected":false},"excerpt":{"rendered":"
codepro \ub54c\ubb38\uc5d0 \ud3ec\uc2a4\ud305\uc744 \ub098\ub220\uc11c \uacc4\uc18d \uc9e4\ub77c\uba39\uc5b4\uc57c \ud558\ub294\uac8c \uc9dc\uc99d\ub098\ub124. delegation : https:\/\/kotlinlang.org\/docs\/delegation.htmlhttps:\/\/kotlinlang.org\/docs\/delegated-properties.html \uc704\uc784(delegation) \ub514\uc790\uc778 \ud328\ud134( https:\/\/en.wikipedia.org\/wiki\/Delegation_pattern )\uc740 \ud55c \ud074\ub798\uc2a4\uc758 \uba64\ubc84 \uad6c\ud604\uc744 \uc9c1\uc811 \ud558\uc9c0 \uc54a\uace0, \ub2e4\ub978 \ud074\ub798\uc2a4\uc758 \uba64\ubc84\uad6c\ud604\uc744 \uc774\uc6a9\ud558\ub294 \uac83\uc774\ub2e4. \ub2e4\uc2dc\ub9d0\ud558\uba74, \ub2e4\ub978 \ud074\ub798\uc2a4\uc5d0\uac8c \uc704\uc784\ud558\ub294 \uac83\uc774\ub2e4. \ucf54\ud2c0\ub9b0\uc740 \uc774\ub97c \uc5b8\uc5b4 \uc218\uc900\uc5d0\uc11c \uc9c1\uc811\uc801\uc73c\ub85c \uc9c0\uc6d0\ud55c\ub2e4. \ubc14\ub85c ‘by’\ud0a4\uc6cc\ub4dc\uac00 \uadf8\uac83\uc774\ub2e4. \uc704 \ucf54\ub4dc\uc5d0\uc11c Window \ud074\ub798\uc2a4\ub294 ClosedShape \uc778\ud130\ud398\uc774\uc2a4\uc758 \uad6c\ud604\uc744 bounds\uc5d0\uac8c \uc704\uc784\ud558\uace0 \uc788\ub2e4. \ud074\ub798\uc2a4 \ub2e8\uc704\uac00 \uc544\ub2c8\ub77c […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[34],"tags":[38,41],"class_list":["post-2605","post","type-post","status-publish","format-standard","hentry","category-kotlin","tag-kotlin","tag-kotlin-kr"],"jetpack_featured_media_url":"","_links":{"self":[{"href":"http:\/\/batmask.net\/index.php\/wp-json\/wp\/v2\/posts\/2605","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/batmask.net\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/batmask.net\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/batmask.net\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/batmask.net\/index.php\/wp-json\/wp\/v2\/comments?post=2605"}],"version-history":[{"count":80,"href":"http:\/\/batmask.net\/index.php\/wp-json\/wp\/v2\/posts\/2605\/revisions"}],"predecessor-version":[{"id":2694,"href":"http:\/\/batmask.net\/index.php\/wp-json\/wp\/v2\/posts\/2605\/revisions\/2694"}],"wp:attachment":[{"href":"http:\/\/batmask.net\/index.php\/wp-json\/wp\/v2\/media?parent=2605"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/batmask.net\/index.php\/wp-json\/wp\/v2\/categories?post=2605"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/batmask.net\/index.php\/wp-json\/wp\/v2\/tags?post=2605"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
\ucc38\uc870\uae00 : 
How to create custom annotations in Kotlin<\/a>
Understanding Kotlin Annotations: A Comprehensive Guide<\/a><\/p>\n\n\n\n