Flutter searching using typeahead

Question

I have a huge json data which I'm loading from assets. I need to search from the recipe's using recipeName and I'm using flutter typeahead to create the search bar and functionalities.

I'm loading all the recipe objects when the app starts. The below code basically returns all the recipes.

  List<RecipeModel> getAllRecipes() {
    for (int i = 0; i < _appData.recipeCategories!.length; i++) {
      for (int j = 0; j < _appData.recipeCategories![i].recipes!.length; j++) {
        _recipeList.add(_appData.recipeCategories![i].recipes![j]);
      }
    }
    return _recipeList;
  }

This code is responsible for the search(Search.dart):

class Search {
  List<RecipeModel> _recipeList = Store.instance.getAllRecipes(); // Store loads data during splash screen
  late RecipeModel recipe;
  RecipeModel returnRecipe(String? suggestion) {
    for (int i = 0; i < _recipeList.length; i++) {
      if (suggestion == _recipeList[i].recipeName) {
        return _recipeList[i];
      }
    }

    return recipe;
  }
}

And now comes the typeahead part. Flutter typeahead takes 4 parameter textFieldConfiguration, suggestionsCallback, itemBuilder, onSuggestionSelected

for suggestionsCallback I'm loading all the recipenames into a list when the screen loads and searching from that list using:

  Future<List<String>> getSuggestions(String str) async {
    return List.of(recipeNamesList).where(
      (recipe) {
        final recipeLower = recipe.toLowerCase();
        final queryLower = str.toLowerCase();

        return recipeLower.contains(queryLower);
      },
    ).toList();
  }

and here's the entire typeahead widget:

  Widget buildSearchTextInput() {
    return Container(
      padding: EdgeInsets.all(10),
      child: TypeAheadFormField<String?>(
        textFieldConfiguration: TextFieldConfiguration(
          controller: _textEditingController,
          focusNode: _focusNode,
          autofocus: true,
          decoration: InputDecoration(
            hintText: "Enter recipe name",
          ),
        ),
        suggestionsCallback: (query) async {
          print("query: $query");
          if (query.length == 0) return [];
          return await getSuggestions(query);
        },
        hideOnEmpty: true,
        itemBuilder: (context, String? suggestion) =>
            SearchResultCard(suggestion: suggestion),
        onSuggestionSelected: (String? suggestion) {
          openRecipeDetailsPage(
            context,
            Search().returnRecipe(suggestion),
          );
        },
      ),
    );
  }

As you can see I'm using the afore mentioned class for a ad-hoc search. Now for openSuggestionsSelected I have to send the user to a recipeDetailsScreen which takes a object of RecipeModel.

1. I was thinking all though I'm going ad-hoc search for this can I reduce the clutter to some extent? I mean apart from the function to load all the recipes in store I have two list to work one. One carries names of the recipes and one carries the all the recipes. Is there a way I can do it using one list?

2. Can I improve the efficiency for the search? I don't think working with two list is a good idea.

N.B: The solution I've written works. I just need something that'll remove the clutter and hopefully reduce the time complexity of the search or at the very least improve functional efficiency.

Answer 1

You can reduce complexity in two ways in your code:

1. Using a Map<String, RecipeModel> for your search part:

class Search {
  // This will still be O(n)
  Map<String, RecipeModel> _map = Map.fromIterable(
    Store.instance.getAllRecipes(),
    key: (recipe) => recipe.name);

  late RecipeModel recipe;

  RecipeModel returnRecipe(String? suggestion) {
    if (suggestion == null) return recipe;
    // This will be O(1) instead of O(n) [better]
    final RecipeModel? found = _map[suggestion];
    return found ?? recipe;
  }
}

2. Using a Trie in your typeahead part (here I'm using trie, but you can use autotrie instead):

 class Search {
  final Map<String, RecipeModel> _map = Map.fromIterable(
    Store.instance.getAllRecipes(),
    key: (recipe) => recipe.name);

  final late Trie trie;

  Search() {
    // This will be O(n)
    trie = Trie.list(map.keys().toList());
  }

  // ...

  List<String> returnSuggestions(String prefix) {
    // This will be O(W*L) instead of O(n^2) [better]
    return trie.getAllWordsWithPrefix(prefix);
  }
}

Changing in your code:

final Search search = Search();

// ...

Widget buildSearchTextInput() {
  return Container(
    padding: EdgeInsets.all(10),
    child: TypeAheadFormField<String?>(
      // ...
      suggestionsCallback: (query) async {
        if (query.isEmpty) return [];
        return search.returnSuggestions(query);
      },
      // ...
      onSuggestionSelected: (String? suggestion) {
        openRecipeDetailsPage(context, search.returnRecipe(suggestion));
      },
    ),
  );
}

You will still have two "lists", but your complexity got better in general.