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[golang] struct の初期化で missing type in composite literal が出た場合の対処

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あんまりハマってる人が居なかったのでメモ。

golang で以下の様に nested な匿名 struct を定義すると、良い感じに初期化できなくてハマった。

type A struct {
  B struct {
    C string
    D string
  }
}

こんな感じで初期化したいけれど、コンパイルエラーになる。

var a = A{
  {
    "foo", // missing type in composite literal
    "bar",
  },
}

こう書かないといけないみたい。

var a = A{
  struct {
    C string
    D string
  }{
    "foo",
    "bar",
  },
}

とりあえず struct の定義を外に出して、下記のようにしてお茶を濁した。

type TypeB struct {
  C string
  D string
}
type A struct {
  B TypeB
}

var a = A{
  TypeB{
    "foo",
    "bar",
  }
}
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