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2428 :: Macro question

• Stefan_Salewski (orginal) [2016-07-31T20:41:27+02:00] view original

  I have this macro, which works fine.

  macro gDefineTypeExtended*(tn, t, tp, f, c: static[string]): stmt =
    var
      cc = indent("\n" & c, 4)
      s = """
  
  proc $2Init(self: $1) {.cdecl.}
  proc $2ClassInit(klass: $1Class) {.cdecl.}
  var $2ParentClass: Gpointer = nil
  var $1PrivateOffset: cint
  proc $2ClassInternInit(klass: Gpointer) {.cdecl.} =
    $2ParentClass = typeClassPeekParent(klass)
    if $1PrivateOffset != 0:
      typeClassAdjustPrivateOffset(klass, $1PrivateOffset)
    
    $2ClassInit(cast[$1Class](klass))
  
  proc $2GetInstancePrivate(self: $1): $1Private {.cdecl.} =
    return cast[$1Private](gStructMemberP(self, $1PrivateOffset))
  
  proc $2GetType*(): GType {.cdecl.} =
    var gDefineTypeIdVolatile {.global.}: Gsize = 0
    if onceInitEnter(addr(gDefineTypeIdVolatile)):
      var gDefineTypeId: GType = registerStaticSimple($3,
                                        internStaticString("$1"),
                                        sizeof($1ClassObj).cuint,
                                        cast[GClassInitFunc]($2ClassInternInit),
                                        sizeof($1Obj).cuint,
                                        cast[GInstanceInitFunc]($2Init),
                                        cast[GTypeFlags]($4))
      $5
      onceInitLeave(addr(gDefineTypeIdVolatile), gDefineTypeId)
    return gDefineTypeIdVolatile
  
  """ % [tn, t, tp, f, cc]
    #echo s
    result = parseStmt(s)
  Run

  But it would be nice if proc $2GetInstancePrivate is not generated when last macro parameter c is "". May it be possible to put a when statement in this macro to opionally suppress generation of proc $2GetInstancePrivate? (Of course I can make a copy of this macro with another name and without that proc)

  [EDIT]

  Indeed I think for this case making a copy of that macro is the best solution -- just did it and it works fine. If we do not want a copy: Divide the string into three parts and joining them, with the second string in a when clause? Like "a" & when "b": b & "c" May that work?

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