E07740: implementation not provided, but services cannot be abstract

What went wrong

A service method doesn't have an implementation body. Unlike abstract classes, services must always provide implementations.

Worked examples

Compilable examples demonstrating this error and the correct fix:

• ek9 -q 1326 (Why does EK9 reject a service method that declares a r...)

Rationale

Services are CONCRETE - all methods must be implemented. There are no abstract service methods.

How to fix it

1. Provide implementation body for the service method

The [EXAMPLE] section below shows a GET method with no body, and the same method giving its response a value.

Common causes

• Forgot to add implementation
• Thinking services support abstract methods

See also

• E07740: service method missing implementation (this error)
• E07800: service method missing return

Examples

Every example is compiled by the EK9 compiler: the first fails exactly as captioned, the others fix it.

Fails with E07740: implementation not provided, but services cannot be abstract

#!ek9
defines module error.e07740.bad

  defines class

    TextResponse with trait of HTTPResponse
      text as String?

      default private TextResponse()

      TextResponse()
        -> body as String
        this.text: body

      override contentType() as pure
        <- rtn as String: "text/plain"

      override content()
        <- rtn as Bytes: Bytes().withUtf8(text)

      override status() as pure
        <- rtn as Integer: 200

      default operator ?

  defines service

    Addresses for :/addresses open

      //A service is never abstract: every method has a body
      byId() as GET for :/{id}
        -> id as String
        <- response as HTTPResponse?

Fixed: Give the service method a body

#!ek9
defines module error.e07740.good

  defines class

    TextResponse with trait of HTTPResponse
      text as String?

      default private TextResponse()

      TextResponse()
        -> body as String
        this.text: body

      override contentType() as pure
        <- rtn as String: "text/plain"

      override content()
        <- rtn as Bytes: Bytes().withUtf8(text)

      override status() as pure
        <- rtn as Integer: 200

      default operator ?

  defines service

    Addresses for :/addresses open

      byId() as GET for :/{id}
        -> id as String
        <- response as HTTPResponse: TextResponse(`address ${id}`)

Questions and answers

These Q&A entries show E07740 and its fix:

• Q1326: Why does EK9 reject a service method that declares a return but has no implementation body?