# `Otera.Loader`
[🔗](https://github.com/georgeguimaraes/otera/blob/v0.2.0/lib/otera/loader.ex#L1)

Loads the templates that `{% extends %}`, `{% include %}` and `{% import %}` name, like the loaders of Jinja2.

The `:loader` option of `Otera.parse/2`, `Otera.load/2` and `Otera.render/3` is one of these:

  * A map from names to sources, like the `DictLoader` of Jinja2:

        Otera.render(~s({% include "header.html" %}), %{}, loader: %{"header.html" => "<h1>Hi</h1>"})
        #=> {:ok, "<h1>Hi</h1>"}

  * A function that gets a name and returns `{:ok, source}`, or `:error` when there is no template with that name, like the `FunctionLoader` of Jinja2. It can also return `{:ok, source, uptodate}`, where `uptodate` is a function without arguments that returns false when the template changed, for `Otera.Cache`.

  * `file_system/1`, which reads the templates from directories, like the `FileSystemLoader` of Jinja2.

The values of a map and the results of a function can also be templates that `Otera.parse/2` made. During a render, Otera loads and parses each template once. To keep the parsed templates for many renders, give an `Otera.Cache` with the `:cache` option.

# `result`

```elixir
@type result() ::
  {:ok, String.t() | Otera.Template.t()}
  | {:ok, String.t(), (-&gt; boolean())}
  | :error
```

# `t`

```elixir
@type t() ::
  %{required(String.t()) =&gt; String.t() | Otera.Template.t()}
  | (String.t() -&gt; result())
```

# `file_system`

```elixir
@spec file_system(Path.t() | [Path.t()]) :: (String.t() -&gt; result())
```

Returns a loader that reads the template `name` from the file `name` in `root`, a directory or a list of directories that it tries in order.

The loader gives an `uptodate` function with each source, which returns false when the modification time or the size of the file changed, for `Otera.Cache`.

The parts of a name are separated by `/`. As in Jinja2, a name with a `..` part is not found, and Otera also refuses a backslash and a null byte, so a template cannot be outside the directories. An empty part and a `.` part do nothing, so `/a.html` is the file `a.html` in a directory. The files are UTF-8.

# `get_source`

```elixir
@spec get_source(t(), String.t()) :: result()
```

Returns the template `name` from `loader`: `{:ok, source_or_template}`, `{:ok, source, uptodate}`, or `:error`.

---

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