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null回避のあたりのリファクタ #141

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kmdkuk opened this issue Sep 23, 2020 · 0 comments
Open

null回避のあたりのリファクタ #141

kmdkuk opened this issue Sep 23, 2020 · 0 comments
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refactor

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@kmdkuk
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kmdkuk commented Sep 23, 2020

概要

  • ?や??を利用する．
  • user?.idでuserがnullのときuser?.idもnullを返す．user.idだともしuserがnullのときエラーが発生する．
  • user ??= User()は，userがnullのときは，User()を代入する式
  • expr1 ?? expr2 は，もしexpr1が非nullのときはその値を返す；そうでなければ、expr2を計算して返す。
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