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33 строки
1.1 KiB
Plaintext
33 строки
1.1 KiB
Plaintext
Attribute-sets
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Attribute sets are an association between string keys and a Nix values.
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Keys can only be strings.
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When writing attribute sets you can also use unquoted identifiers as keys.
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nix-repl> s = { foo = "bar"; a-b = "baz"; "123" = "num"; }
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nix-repl> s
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{ "123" = "num"; a-b = "baz"; foo = "bar"; }
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For those reading Nix expressions from nixpkgs: do not confuse attribute sets with argument sets used in functions.
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To access elements in the attribute set:
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nix-repl> s.a-b
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"baz"
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nix-repl> s."123"
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"num"
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Yes, you can use strings to address keys which aren't valid identifiers.
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Inside an attribute set you cannot normally refer to elements of the same attribute set:
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nix-repl> { a = 3; b = a+4; }
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error: undefined variable `a' at (string):1:10
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To do so, use recursive attribute sets:
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https://nixos.org/manual/nix/stable/#idm140737321983744
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nix-repl> rec { a = 3; b = a+4; }
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{ a = 3; b = 7; }
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This is very convenient when defining packages, which tend to be recursive attribute sets.
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