Asynxronous Datastreaming with Kotlin Flow

kotlin conf

Transcript

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

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2. 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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3. 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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4. List vs Channel
   

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5. 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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6. 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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7. 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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8. Channel vs Flow
   

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9. 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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10. 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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11. 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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12. List vs Flow
    

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13. 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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14. 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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15. List vs Flow
    bufferを使うがよい
    

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

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17. 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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18. 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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19. 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
    

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