Question

我打算输出这个：

columns = ["id","name","col1","col2"]
rows = [10, "foo", "val1", "val2" ]
Enum.zip(columns, rows) |> Enum.into(%{})

=> %{"col1" => "val1", "col2" => "val2", "id" => 10, "name" => "foo"}

但遗憾的是rows是一个嵌套列表，例如：[[10, "foo", "val1", "val2" ]]，因此上面的代码会返回：

=> %{"id" => [10, "foo", "val1", "val2"]}

如何访问内部列表的第一个元素？我试过了rows[0]，但那没用。

Answer 1

您可以使用核心函数hd/1

从列表中提取第一项

columns = ["id","name","col1","col2"]
rows = [[10, "foo", "val1", "val2" ]]
Enum.zip(columns, hd(rows)) |> Enum.into(%{})
%{"col1" => "val1", "col2" => "val2", "id" => 10, "name" => "foo"}

如果您有多行，则可以映射行：

columns = ["id","name","col1","col2"]
rows = [[10, "foo", "val1", "val2"], [20, "bar", "val3", "val4"]]
Enum.map(rows, &(Enum.zip(columns, &1) |> Enum.into(%{})))
[
  %{"col1" => "val1", "col2" => "val2", "id" => 10, "name" => "foo"},
  %{"col1" => "val3", "col2" => "val4", "id" => 20, "name" => "bar"}
]

如何在Elixir中移动嵌套列表

1 个答案: