## Creating Code Snippets

In general, creating application snippets can be accomplished with the following
syntax inside of the dartdoc comment for a Flutter class/variable/enum/etc.:

```dart
/// {@tool snippet --template=stateful_widget}
/// Any text outside of the code blocks will be accumulated and placed at the
/// top of the snippet box as a description. Don't try and say "see the code
/// above" or "see the code below", since the location of the description may
/// change in the future. You can use dartdoc [Linking] in the description, and
/// __Markdown__ too.
/// 
/// ```dart preamble
/// class Foo extends StatelessWidget {
///   const Foo({this.value = ''});
/// 
///   String value; 
/// 
///   @override
///   Widget build(BuildContext context) {
///     return Text(value);
///   }
/// }
/// ```
/// This will get tacked on to the end of the description above, and shown above
/// the snippet.  These two code blocks will be separated by `///...` in the
/// short version of the snippet code sample.
/// ```dart
/// String myValue = 'Foo';
/// 
/// @override
/// Widget build(BuildContext) {
///   return const Foo(myValue);
/// }
/// ```
/// {@end-tool}
```

This will result in the template having the section that's inside "```dart"
interpolated into the template's stateful widget's state object body.

All code within a code block in a snippet needs to be able to be run through
dartfmt without errors, so it needs to be valid code (This shouldn't be an
additional burden, since all code will also be compiled to be sure it compiles).

## Available Templates

The templates available for using as an argument to the snippets tool are as
follows:

- [`freeform`](freeform.tmpl) :
  This is a simple template for which you provide everything.  It has no code of
  its own, just the sections for `imports`, `main`, and `preamble`. You must
  provide the `main` section in order to have a `main()`.

- [`stateful_widget`](stateful_widget.tmpl) :
  The default code block will be placed as the body of the `State` object of a
  StatefulWidget subclass. Because the default code block is placed as the body
  of a stateful widget, you will need to implement the `build()` function, and any
  state variables. It also has a `preamble` in addition to the default code
  block, which will be placed at the top level of the Dart file, so bare
  function calls are not allowed in the preamble.  It also has an `imports`
  section to import additional packages. Please only import things that are part
  of flutter or part of default dependencies for a `flutter create` project.
  It creates a WidgetsApp around the child stateful widget.

- [`stateless_widget`](stateless_widget.tmpl) :
  Identical to the `stateful_widget` template, except that the default code
  block is inserted as the `build` function in a
  StatelessWidget. There is no need to include the @override before the build
  funciton (the template adds this for you).

- [`stateful_widget_material`](stateful_widget_material.tmpl) : Similar to
  `stateful_widget`, except that it imports the material library, and uses
  a MaterialApp instead of WidgetsApp.

- [`stateless_widget_material`](stateless_widget_material.tmpl) : Similar to
  `stateless_widget`, except that it imports the material library, and uses
  a MaterialApp instead of WidgetsApp.

- [`stateful_widget_scaffold`](stateful_widget_scaffold.tmpl) : Similar to
  `stateful_widget_material`, except that it wraps the stateful widget with a
  Scaffold.

- [`stateless_widget_scaffold`](stateless_widget_scaffold.tmpl) : Similar to
  `stateless_widget_material`, except that it wraps the stateless widget with a
  Scaffold.
