Type Safety & Query Keys

Fasq is designed to be fully type-safe. Using TypedQueryKey allows you to enforce type constraints between your query keys and the data they return, preventing runtime casting errors.

[!TIP] To automate serializer registration for complex data types and eliminate manual boilerplate, check out the fasq_serializer_generator package.

TypedQueryKey

A TypedQueryKey<T> binds a specific data type T to a query key string.

Definition


// Define keys with their expected return types
final userKey = TypedQueryKey<User>('user', User);
final postsKey = TypedQueryKey<List<Post>>('posts', List<Post>);

Usage with QueryBuilder

When you use a TypedQueryKey, QueryBuilder (and QueryClient) infer the data type automatically.


QueryBuilder(
  queryKey: userKey, // T is inferred as User
  queryFn: () => fetchUser(),
  builder: (context, state) {
    // state.data is strictly typed as User?
    // No casting required: (state.data as User)
    return Text(state.data?.name ?? 'Loading...');
  },
)

Parameterized Keys

TypedQueryKey also supports parameters while maintaining type safety.


// Base key for a detail view
final todoDetailKey = TypedQueryKey<Todo>('todo', Todo);
 
// Generate a specific key for ID '123'
// The resulting key is still a TypedQueryKey<Todo>
final myTodoKey = todoDetailKey.withParam('123');