MyLittleSuite/dart_mapperdart_mapper

Multi-Source Mapping

Combine multiple source parameters into a single target object.

Multi-Source Mapping

A mapper method can accept more than one source parameter. The generator resolves target fields from all sources automatically.

Basic Multi-Source

Declare multiple parameters — the generator picks up fields from each:

class UserInfo {
  final String name;
  final int age;
  const UserInfo({required this.name, required this.age});
}

class CompanyInfo {
  final String companyName;
  final String department;
  const CompanyInfo({required this.companyName, required this.department});
}

class EmployeeProfile {
  final String name;
  final int age;
  final String companyName;
  final String department;
  const EmployeeProfile({
    required this.name,
    required this.age,
    required this.companyName,
    required this.department,
  });
}

@Mapper()
abstract class EmployeeMapper {
  EmployeeProfile toProfile(UserInfo user, CompanyInfo company);
}

Generated:

@override
EmployeeProfile toProfile(UserInfo user, CompanyInfo company) {
  return EmployeeProfile(
    name: user.name,
    age: user.age,
    companyName: company.companyName,
    department: company.department,
  );
}

Resolving Ambiguity

If two source parameters have fields with the same name, the generator cannot resolve which to use and produces a build error. Use @Mapping(source: 'paramName.fieldName') to qualify:

class Primary {
  final String label;
  const Primary({required this.label});
}

class Secondary {
  final String label;
  const Secondary({required this.label});
}

class Result {
  final String label;
  const Result({required this.label});
}

@Mapper()
abstract class ResultMapper {
  @Mapping(target: 'label', source: 'primary.label')
  Result combine(Primary primary, Secondary secondary);
}

Combining with @Mapping

Any @Mapping annotation applies to the combined view of all sources. Field renames, ignores, expressions, and dot-notation all work normally with multi-source methods:

@Mapper()
abstract class EmployeeMapper {
  @Mapping(target: 'displayName', expression: r'${user.name} @ ${company.companyName}')
  @Mapping(target: 'departmentCode', source: 'company.department')
  EmployeeProfile toProfile(UserInfo user, CompanyInfo company);
}

See Also

Edit this page on GitHub
Enum Mapping
Dot Notation