Transform

What it is

transform maps the result of a wrapped function from one type to another.

When to use it

  • Adapting between different data representations.
  • Normalising input before processing.
  • Converting internal models to DTOs and back.

API reference 

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// api-reference
// On Func<R1>
Func<R2> transform<R2>(R2 Function(R1 result) mapper);

// On Func1<T, R1>
Func1<T, R2> transform<R2>(R2 Function(R1 result) mapper);

// On Func2<T1, T2, R1>
Func2<T1, T2, R2> transform<R2>(R2 Function(R1 result) mapper);

Parameters

ParameterTypeDescription
mapperR2 Function(R1)Maps the wrapped function’s result to a new type.

Examples

Basic example 

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final toUpper = Func1<String, String>((s) async => s.toUpperCase());

final transform = toUpper.transform<String>((s) => s.trim());

print(await transform('  hello  ')); // HELLO

Real-world example 

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final transform = Func1<ApiRequest, String>((req) async {
  return await api.post(req.toString()) as String;
}).transform<DomainModel>((response) => DomainModel());

await transform(ApiRequest());

Best practices

  • Keep mappers pure and synchronous.
  • Handle nulls and edge cases inside mappers to avoid surprising the target.

Common pitfalls

  • Type mismatch: Mappers must match the generic types exactly; otherwise the code will not compile.
  • Mapper exceptions: Exceptions thrown in mappers propagate to the caller.