E07750: Web Service return type must be compatible with HTTPResponse

What went wrong

A service method returns a type that isn't compatible with HTTPResponse.

Worked examples

Compilable examples demonstrating this error and the correct fix:

• ek9 -q 890 (Why must service operations return HTTPResponse in EK9?)

How to fix it

1. Return HTTPResponse or compatible type
2. Wrap data in HTTPResponse constructor

Common causes

• Returning raw data type instead of HTTPResponse
• Missing HTTPResponse wrapper

See also

• E07750: service method wrong return type (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 E07750: Web Service return type must be compatible with HTTPResponse

#!ek9
defines module error.e07750.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

    Numbers for :/numbers open

      //A service method answers with an HTTPResponse
      count() as GET for :/count
        <- total as Integer: 42

Fixed: Return an HTTPResponse carrying the value

#!ek9
defines module error.e07750.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

    Numbers for :/numbers open

      count() as GET for :/count
        <- response as HTTPResponse: TextResponse($42)

Questions and answers

These Q&A entries show E07750 and its fix:

• Q890: Why must service operations return HTTPResponse in EK9?