Notes on How to Name Things in Scala (and Java)

Some notes on how to name things in Scala and Java

Variable and Function Naming

There’s a great language-agnostic naming guide I often reference.

Some things I see in the wild:

No active verb in the function name

Examples:

• def matchingRateCard (should be matchRateCard)
• def calculationPrice (should be calculatePrice)

Verbs as Nouns

initialCardCreates <- determineInitialCustomerCardCreates(customer): CardCreate
// should be
cardCreateCommands <- determineInitialCustomerCardCreateCommands(customer): CardCreateCommand

Leaking Implementation Details

I see AccountDto in the API spec. Use Account instead.

package org.bargsten.banking.transaction.swift.api.dto

// Don't name it AccountDto. You are already in the dto package AND
// having the suffix "Dto" in your (REST) API looks somewhat unprofessional.
case class Account(
    id: String,
    name: String,
    balance: BigDecimal,
)

If you have to map from core/domain to dto, you can import the packages only, but not the models.

import org.bargsten.banking.transaction.swift.api.dto
import org.bargsten.banking.transaction.swift.core

Use dto.Account and core.Account to distinguish.

Using request/response naming, e.g. AccountRequest and AccountResponse is also a common pattern.

See Also

• Naming conventions  |  Cloud API Design Guide  |  Google Cloud
• GitHub - kettanaito/naming-cheatsheet: Comprehensive language-agnostic guidelines on variables naming. Home of the A/HC/LC pattern.