# `Otera.Undefined`
[🔗](https://github.com/georgeguimaraes/otera/blob/v0.1.0/lib/otera/undefined.ex#L1)

The value of a missing variable, attribute or item, like the default `Undefined` of Jinja2.

An undefined value prints as an empty string, is false, has a length of 0 and iterates as an empty sequence. Other operations on it, such as arithmetic, calls or attribute lookup, raise an `Otera.Error` with the message that Jinja2 gives, for example `'user' is undefined`.

A custom filter, test or function can receive an undefined value as an argument.

# `t`

```elixir
@type t() :: %Otera.Undefined{
  hint: String.t() | nil,
  kind: atom(),
  name: term(),
  obj: term()
}
```

# `fail`

```elixir
@spec fail(t()) :: no_return()
```

Raises the error of an operation on `undefined`.

# `message`

```elixir
@spec message(t()) :: String.t()
```

Returns the message of the error that an operation on `undefined` raises.

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*Consult [api-reference.md](api-reference.md) for complete listing*