Re: get a type via a string?

[jasper]

You can get the ssn typedef with this: 


macro ssnTypeImpl(T: typedesc): untyped =
  let ssnField = T.getType[1].getType[2][1]
  echo ssnField.getTypeInst.getImpl.treeRepr

ssnTypeImpl(Person)


Run

Re: get a type via a string?

[mratsim]

Here you go


import macros, options

type
  ssnType = Option[int]

type
  Person = object
age: Option[int]
ssn: ssnType

proc isOptionInt(x: NimNode): bool =
  sameType(x, getType(Option[int]))

macro checkOptionInt(x: typed): untyped =
  result = newLit(x.isOptionInt)

echo checkOptionInt(typeof(Person().ssn))


Run

Note that you can turn a typedesc into a NimNode with `getType`, but there is 
no way to turn a NimNode representing a type back to a typedesc, and the 
corresponding feature request was closed 
([https://github.com/nim-lang/Nim/issues/6785)](https://github.com/nim-lang/Nim/issues/6785\)),
 so keep your typedescs around as long as possible.

Re: get a type via a string?

[kaushalmodi]

This is very related: 
[https://forum.nim-lang.org/t/5027#31537](https://forum.nim-lang.org/t/5027#31537).
 Does that help? 

get a type via a string?

[JohnAD]

I'm writing a macro that parses over object types and generates various 
functions on it's fields. For the most part it works.

However, I'm will likely encountering folks trying to do this:


type
  ssnType = Option[int]

type
  Person = object
age: Option[int]
ssn: ssnType


Run

My macro can handle the "age" field because it's true type is easily parsed in 
the Node tree. Both "Option" and "int" are known types and in a bracket. Got it.

"ssnType" is also visible, but that is an unknown type made by the library user.

Is there a way, given the string or symbol "ssnType", to somehow glean it's 
earlier definition of "Option[int]"?

I've tried various plays with `getTypeImpl` and `getTypeImpl`, but I suspect 
I'm missing some key knowledge.