如何在宏中迭代元组/对象的字段（名称+类型）？

我找到了该问题的解决方案，它似乎工作正常，但我不确定是否有更好的替代方案。该解决方案是基于使用getTypeImpl的typed参数。要了解它是如何工作的，查看t.getTypeImpl.treeRepr简单元组和对象的输出会有所帮助。

• 元组：例如类型 impl AST(x: 0, y: 1, name: "")看起来像这样：

  TupleTy
    IdentDefs
      Sym "x"
      Sym "int"
      Empty
    IdentDefs
      Sym "y"
      Sym "int"
      Empty
    IdentDefs
      Sym "name"
      Sym "string"
      Empty
  

  注：typeKind的getTypeImplISntyTuple

• Object：具有相同结构的对象的类型 impl AST 将是：

  ObjectTy
    Empty
    Empty
    RecList
      IdentDefs
        Sym "x"
        Sym "int"
        Empty
      IdentDefs
        Sym "y"
        Sym "int"
        Empty
      IdentDefs
        Sym "name"
        Sym "string"
        Empty
  

  注：typeKind的getTypeImplISntyObject

这表明我们正在寻找的信息在IdentDefs. 我们只需要确保适当地处理元组和对象：对于元组，IdentDefs是的直接子级NimNode，而对于对象，IdentDefs将存储在索引2的子级中（索引0的子级包含编译指示信息，索引中的子级1 是关于父母的信息）。

总体而言，宏可能看起来像（添加了一些调试输出以进行说明）：

macro iterateFields*(t: typed): untyped =
  echo "--------------------------------"

  # check type of t
  var tTypeImpl = t.getTypeImpl
  echo tTypeImpl.len
  echo tTypeImpl.kind
  echo tTypeImpl.typeKind
  echo tTypeImpl.treeRepr

  case tTypeImpl.typeKind:
  of ntyTuple:
    # For a tuple the IdentDefs are top level, no need to descent
    discard
  of ntyObject:
    # For an object we have to descent to the nnkRecList
    tTypeImpl = tTypeImpl[2]
  else:
    error "Not a tuple or object"

  # iterate over fields
  for child in tTypeImpl.children:
    if child.kind == nnkIdentDefs:
      let field = child[0] # first child of IdentDef is a Sym corresponding to field name
      let ftype = child[1] # second child is type
      echo "Iterating field: " & $field & " -> " & $ftype
    else:
      echo "Unexpected kind: " & child.kind.repr
      # Note that this can happen for an object with a case
      # fields, which would give a child of type nnkRecCase.
      # How to handle them depends on the use case.

# small test
type
  TestObj = object
    x: int
    y: int
    name: string

let t = (x: 0, y: 1, name: "")
let o = TestObj(x: 0, y: 1, name: "")

iterateFields(t)
iterateFields(o)