Nim: [RFC] update object syntax: obj.updateObj(field1 = foo, field2 = "bar")

[timotheecour]

The following seems quite useful, I wonder whether it's already in stdlib ? If not would that belong in system.nim ?

import macros
import strformat

macro updateObj*(src: typed, n: varargs[untyped]): typed =
  result = newNimNode(nnkStmtList, n)
  for x in n:
    let cmd = fmt"{toStrLit(src)}.{toStrLit(x)}"
    # or: let cmd = $(toStrLit(src)) & "." & $(toStrLit(x))
    result.add(parseStmt(cmd))

# usage:
type Foo=object
  a:string
  b:int
  c:seq[string]
  d:bool

proc test_updateObj*()=
  var opt: Foo
  opt.updateObj(b = 3 - 5, a="asdf", c = @["baz", """ ? """], d=true)
  echo opt

[hlaaftana]

Heads up: toStrLit(x) is just newStrLitNode(repr(x)), $toStrLit(x) is just repr(x).

This macro could be more generalized in a tap or doto macro as in ruby or clojure and that wouldn't really fit in with the stdlib in my opinion, instead some general utility Nimble package.

[andreaferretti]

There is also automatic self insertion that, while not the same thing, may be used in similar cases

[dom96]

I vote for this to be made put in a Nimble package. If it becomes popular enough we can adopt it into the stdlib later.

[timotheecour]

ok, closing in favor of nimble package

[hlaaftana]

I'm surprised I didn't remember this before, but this is already in the package cascade