decodeGridDelegate static method

SliverGridDelegate decodeGridDelegate({ required dynamic gridDelegate, })

Implementation

static SliverGridDelegate decodeGridDelegate({
  required dynamic gridDelegate,
}) {
  SliverGridDelegate? result;

  var createException = (message) => Exception('''
$message

1. "delegate": {
"type": "max_cross_axis_extent",
"childAspectRatio": "<double?>",
"crossAxisSpacing": "<double?>",
"mainAxisExtent": "<double?>",
"mainAxisSpacing": "<double?>",
"maxCrossAxisExtent": "<double>"
}

2. "delegate": {
"type": "fixed_cross_axis_count",
"crossAxisCount": "<int>",
"childAspectRatio": "<double?>",
"crossAxisSpacing": "<double?>",
"mainAxisExtent": "<double?>",
"mainAxisSpacing": "<double?>"
}''');

  if (gridDelegate is SliverGridDelegate) {
    result = gridDelegate;
  } else if (gridDelegate != null) {
    var delegate = gridDelegate;
    if (delegate is String &&
        (delegate.startsWith('{') && delegate.endsWith('}'))) {
      try {
        delegate = json.decode(delegate);
      } catch (e) {
        // no-op; it isn't JSON
      }
    }

    var type = delegate['type'] ?? 'maxCrossAxisExtent';
    switch (type) {
      case 'max_cross_axis_extent':
        result = SliverGridDelegateWithMaxCrossAxisExtent(
          childAspectRatio:
              JsonClass.parseDouble(delegate['childAspectRatio']) ?? 1.0,
          crossAxisSpacing:
              JsonClass.parseDouble(delegate['crossAxisSpacing']) ?? 0.0,
          mainAxisExtent: JsonClass.parseDouble(delegate['mainAxisExtent']),
          mainAxisSpacing:
              JsonClass.parseDouble(delegate['mainAxisSpacing']) ?? 0.0,
          maxCrossAxisExtent:
              JsonClass.parseDouble(delegate['maxCrossAxisExtent'])!,
        );
        break;

      case 'fixed_cross_axis_count':
        result = SliverGridDelegateWithFixedCrossAxisCount(
          crossAxisCount: JsonClass.parseInt(delegate['crossAxisCount'])!,
          childAspectRatio:
              JsonClass.parseDouble(delegate['childAspectRatio']) ?? 1.0,
          crossAxisSpacing:
              JsonClass.parseDouble(delegate['crossAxisSpacing']) ?? 0.0,
          mainAxisExtent: JsonClass.parseDouble(delegate['mainAxisExtent']),
          mainAxisSpacing:
              JsonClass.parseDouble(delegate['mainAxisSpacing']) ?? 0.0,
        );
        break;

      default:
        throw createException('''
[grid_builder]: Unknown delegate type encountered: [$type].  To resolve this add
a delegate arg that follows one of the two structures:''');
    }
  } else {
    throw Exception('''
[grid_builder]: A null value was passed in as the grid delegate despite the
delegate infor being required.
''');
  }

  return result;
}