kotlin - 惯用箭头

Question

我有以下方法：

internal typealias MaybeError<T> = Either<GenericError, T>

override fun createCompany(companyDomain: CompanyDomain): MaybeError<CompanyDomain> =
    checkCompany(companyDomain).map { it.toEntity() }.fold({ Either.left(it) }) { company ->
        with (companyRepository) {
            isCompanyExists(company).fold({ Either.left(it) }) { isExists ->
                if (isExists) return@with Either.left(CompanyNameExists(companyDomain))
                createCompany(company).fold({ Either.right(companyDomain) }) { Either.left(it) }
            }
        }
    }

有没有更好/更惯用的方式来使用 Arrow 编写这个？

Answer 1

很难重构，因为我只能假设使用过的方法应该返回什么。但我猜这些方法会返回MaybeError。在这种情况下，我们可以省略fold({ Either.left(it) })，我们可以使用mapor flatMap。

internal typealias MaybeError<T> = Either<GenericError, T>

override fun createCompany(companyDomain: CompanyDomain): MaybeError<CompanyDomain> =
    checkCompany(companyDomain)
        .map { it.toEntity() }
        .flatMap { company ->
            companyRepository.isCompanyExists(company)
                .flatMap { isExists ->
                    if (isExists) {
                        MaybeError.left(CompanyNameExists(companyDomain))
                    } else {
                        companyRepository.createCompany(company)
                    }
                }
        }