applyVariants method

Style applyVariants(List<Variant> selectedVariants)

Selects multiple Variant instances and returns a new Style with the selected variants.

If the applyVariants list is empty, returns this mix without any changes. Otherwise, the method merges the attributes of the selected variants into a new Style instance.

Example: final outlinedVariant = Variant('outlined'); final smallVariant = Variant('small'); final style = Style( attr1, attr2, outlinedVariant(attr3, attr4), smallVariant(attr5), ); final outlinedSmallMix = style.applyVariants(outlinedVariant, smallVariant);

In this example:
- Two `Variant` instances `outlinedVariant` and `smallVariant` are created.
- An initial `Style` instance `style` is created with `attr1` and `attr2`, along with the two variants.
- The `applyVariants` method is called on the `Style` instance with a list of `outlinedVariant` and `smallVariant` as the argument.
- The `applyVariants` method returns a new `Style` instance `outlinedSmallMix` with the attributes of the selected variants merged.
- The resulting `outlinedSmallMix` is equivalent to `Style(attr1, attr2, attr3, attr4, attr5)`.

Note:
The attributes from the selected variants (`attr3`, `attr4`, and `attr5`) are not applied to the `Style` instance until the `applyVariants` method is called.

Implementation

Style applyVariants(List<Variant> selectedVariants) {
  /// Return the original Style if no variants were selected
  if (selectedVariants.isEmpty) {
    return this;
  }

  /// Initializing two empty lists that store the matched and remaining `Variants`, respectively.
  final matchedVariants = <VariantAttribute>[];
  final remainingVariants = <VariantAttribute>[];

  /// Loop over all VariantAttributes in variants only once instead of a nested loop,
  /// checking if each one matches with the selected variants.
  /// If it does, add it to the matchedVariants, else add it to remainingVariants.
  for (final variant in variants.values) {
    if (variant.matches(selectedVariants)) {
      matchedVariants.add(variant);
    } else {
      final remainingVariant = variant.removeVariants(selectedVariants);
      if (remainingVariant != null) {
        remainingVariants.add(remainingVariant);
      }
    }
  }

  final updatedStyle = Style._(
    styles: styles,
    variants: AttributeMap(remainingVariants),
  );

  /// If not a single variant was matched, return the original Style.
  if (matchedVariants.isEmpty) {
    return updatedStyle;
  }

  /// Create a Style from the matched variants.
  final styleToApply =
      Style.combine(matchedVariants.map((e) => e.value).toList());

  /// Merge the new Style created with the existing Style, excluding the matched variants.
  final mergedStyle = updatedStyle.merge(styleToApply);

  /// Apply all variants and return the final Style.
  return mergedStyle.applyVariants(selectedVariants);
}