Asynxronous Datastreaming with Kotlin Flow

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Asynchronous Data Streams with Kotlin Flow を要約したかった

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自己紹介 @sobaya15 : Twitter @sobaya-0141 :Github @sobaya : Qiita Android iOS 今すぐインストール！いろんな人を募集してます！！お気軽にお声がけください

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やることリスト・List vs Channel ・Channel vs Flow ・List vs Flow ・元ネタや参考情報

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List vs Channel

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List vs Channel runBlocking { val list = getList() list.forEach { Log.d("LIST", "PRINT $it") } } runBlocking { val channel = getChannelList() for (result in channel) { Log.d("CHANNEL", "PRINT $result") } } List Channel Log.d("LIST", "BEFORE ADD A") list.add("A") Log.d("LIST", "AFTER ADD A") Log.d("CHANNEL", "BEFORE SEND A") send("A") Log.d("CHANNEL", "AFTER SEND A")

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List vs Channel 2020-01-09 12:04:57.588 15021-15021/com.example.myapplication D/LIST: BEFORE ADD A 2020-01-09 12:04:57.589 15021-15021/com.example.myapplication D/LIST: AFTER ADD A 2020-01-09 12:04:57.589 15021-15021/com.example.myapplication D/LIST: BEFORE ADD B 2020-01-09 12:04:57.589 15021-15021/com.example.myapplication D/LIST: AFTER ADD B 2020-01-09 12:04:57.589 15021-15021/com.example.myapplication D/LIST: BEFORE ADD C 2020-01-09 12:04:57.589 15021-15021/com.example.myapplication D/LIST: AFTER ADD C 2020-01-09 12:04:57.589 15021-15021/com.example.myapplication D/LIST: PRINT A 2020-01-09 12:04:57.589 15021-15021/com.example.myapplication D/LIST: PRINT B 2020-01-09 12:04:57.589 15021-15021/com.example.myapplication D/LIST: PRINT C List print() getList() A B C A B C

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List vs Channel 2020-01-09 12:06:44.706 15021-15021/com.example.myapplication D/CHANNEL: BEFORE SEND A 2020-01-09 12:06:44.706 15021-15021/com.example.myapplication D/CHANNEL: AFTER SEND A 2020-01-09 12:06:44.706 15021-15021/com.example.myapplication D/CHANNEL: BEFORE SEND B 2020-01-09 12:06:44.707 15021-15021/com.example.myapplication D/CHANNEL: PRINT A 2020-01-09 12:06:44.708 15021-15021/com.example.myapplication D/CHANNEL: PRINT B 2020-01-09 12:06:44.708 15021-15021/com.example.myapplication D/CHANNEL: AFTER SEND B 2020-01-09 12:06:44.708 15021-15021/com.example.myapplication D/CHANNEL: BEFORE SEND C 2020-01-09 12:06:44.708 15021-15021/com.example.myapplication D/CHANNEL: AFTER SEND C 2020-01-09 12:06:44.710 15021-15021/com.example.myapplication D/CHANNEL: PRINT C Channel print() getList() A B C Channel A B C

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Channel vs Flow

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Channel vs Flow val ﬂow = getFlowList() ﬂow.collect { result -> Log.d("FLOW", "PRINT $result") } Flow Log.d("FLOW", "BEFORE EMIT A") emit("A") Log.d("FLOW", "AFTER EMIT A") runBlocking { val channel = getChannelList() for (result in channel) { Log.d("CHANNEL", "PRINT $result") } } Channel Log.d("CHANNEL", "BEFORE SEND A") send("A") Log.d("CHANNEL", "AFTER SEND A")

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Channel vs Flow Channel print() getList() Channel A B C runBlocking { val channel = getChannelList() for (result in channel) { Log.d("CHANNEL", "PRINT $result") } } ファイル読み込みとか通信だったらcloseされない

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Channel vs Flow Flow print() getList() Flow A B C val ﬂow = getFlowList() ﬂow.collect { result -> Log.d("FLOW", "PRINT $result") } collect A B C collectしなきゃ動かないから安心

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List vs Flow

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List vs Flow List print() getList() A B C A B C Flow print() getList() A B C A C B

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List vs Flow 処理が交互に行われるようになっただけじゃね？？？

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List vs Flow bufferを使うがよい

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List vs Flow Flow val ﬂow = getFlowList() ﬂow.buffer().collect { result -> Log.d("FLOW", "PRINT $result") }

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List vs Flow print() getList() Flow collect 2020-01-10 12:50:16.181 11661-11661/com.example.myapplication D/FLOW: BEFORE EMIT A 2020-01-10 12:50:16.182 11661-11661/com.example.myapplication D/FLOW: AFTER EMIT A 2020-01-10 12:50:16.182 11661-11661/com.example.myapplication D/FLOW: BEFORE EMIT B 2020-01-10 12:50:16.182 11661-11661/com.example.myapplication D/FLOW: AFTER EMIT B 2020-01-10 12:50:16.182 11661-11661/com.example.myapplication D/FLOW: BEFORE EMIT C 2020-01-10 12:50:16.182 11661-11661/com.example.myapplication D/FLOW: AFTER EMIT C 2020-01-10 12:50:16.182 11661-11661/com.example.myapplication D/FLOW: PRINT A 2020-01-10 12:50:16.182 11661-11661/com.example.myapplication D/FLOW: PRINT B 2020-01-10 12:50:16.182 11661-11661/com.example.myapplication D/FLOW: PRINT C A B C A B C

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List vs Flow ・紹介したように引数なしでbufferを呼んだ場合は64個が上限でバッファしてくれる・バッファサイズを任意に指定可能・UNLIMITEDを指定すると無制限(Int.MAX_VLUE) バッファサイズ以外に動作も指定できるので、単純に順番通りの値が欲しい場合以外には調べてもらえるといいかもです。

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元ネタや参考情報公式 https://www.youtube.com/watch?v=tYcqn48SMT8&t=1401s https://kotlinlang.org/docs/reference/coroutines/flow.html YouTube https://satoshun.github.io/2019/08/flow-buffer/ bufferに関するブログ発表に使ったサンプルコード https://github.com/sobaya-0141/CoroutineSample