https://itome.team/blog/2019/12/flutter-advent-calendar-day3/
https://itome.team/blog/2019/12/flutter-advent-calendar-day4/
https://qiita.com/kikuchy/items/2cce118d38fc15324b2b
https://qiita.com/tokkun5552/items/4649478803be47cd488c
https://qiita.com/teradonburi/items/913fb8c311b9f2bdb1dd
https://logmi.jp/tech/articles/303939
https://codezine.jp/article/detail/13498
https://codezine.jp/article/detail/13586
https://codezine.jp/article/detail/13665
https://qiita.com/mkosuke/items/42c19d7edbf111f7fb71
https://zenn.dev/tris/articles/bf623e5e65fac3
https://note.com/iwatsuru/n/n8fd68f552926
https://enjoy-a-lot.com/dart-methods/
https://qiita.com/dennougorilla/items/170deacf178891ced41e

Constructor

https://dev.classmethod.jp/articles/about_dart_constructors/
https://makicamel.hatenablog.com/entry/2019/03/14/213933
https://flutter.keicode.com/dart/constructor.php
https://www.cresc.co.jp/tech/java/Google_Dart2/language/classes/classes.html#__RefHeading__63845_1385182067
https://zenn.dev/iwaku/articles/2020-12-08-iwaku
https://qiita.com/naoaki_kaito/items/9ea5d956d5d6e23c5d6a

名前付き引数

https://qiita.com/akatsukaha/items/497b8990f2a97f64d8d3

Cascade notation

https://www.meganii.com/blog/2020/02/20/dart-cascade-notation/
https://www.cresc.co.jp/tech/java/Google_Dart2/language/operators/operators.html#__RefHeading__9605_1005113362
https://qiita.com/Nedward/items/b71512f8c2997f52697d
https://stackoverflow.com/questions/49447736/list-use-of-double-dot-in-dart
https://codezine.jp/article/detail/13880
https://twitter.com/_mono/status/1163999422818074626?s=20

Spread Operator

https://stackoverflow.com/questions/57900901/whats-the-usage-of-three-dots-in-dart-list
https://developer.mozilla.org/ja/docs/Web/JavaScript/Reference/Operators/Spread_syntax
https://typescript-jp.gitbook.io/deep-dive/future-javascript/spread-operator
https://twitter.com/_mono/status/1227562969136918528

数値かどうかを調べる

https://qiita.com/t__k/items/2dbde25718c35f2c4fee
https://stackoverflow.com/questions/24085385/checking-if-string-is-numeric-in-dart
https://qiita.com/masashi-sutou/items/8bf1b0dab2850c3024fc

mapのindex

https://stackoverflow.com/questions/54990716/flutter-get-iteration-index-from-list-map
https://fireship.io/snippets/dart-how-to-get-the-index-on-array-loop-map/

Future async/await

https://www.youtube.com/watch?v=OTS-ap9_aXc
https://www.youtube.com/watch?v=SmTCmDMi4BY
https://zenn.dev/iwaku/articles/2020-12-29-iwaku
https://qiita.com/arthur_foreign/items/4d85423e9307512237da
https://sbfl.net/blog/2015/01/05/writing-asynchronous-operation-with-future-in-dart/
https://flutternyumon.com/how-to-use-future/
https://flutternyumon.com/how-to-use-async-and-await/

Stream

https://www.youtube.com/watch?v=nQBpOIHE4eE
https://zenn.dev/iwaku/articles/2020-12-10-iwaku
https://zenn.dev/kakerun/articles/bfdf9ccee3db6e1f58ca
http://www.cresc.co.jp/tech/java/Google_Dart2/language/asynchrony_streams/asynchrony_streams.html