My macro:
import macros
macro createObj(typ: typedesc, data: untyped): untyped =
# This macro only accepts tuples in parenthesis, but this can be changed
assert data.kind == nnkPar
# Object construction syntax
result = newTree(nnkObjConstr)
# Add type name
result.add(typ.getTypeInst()[1])
# Get implementation of typedesc
let typImpl = typ.getTypeInst()[1].symbol.getImpl()[2]
# We support both ref and usual objects
let fields = if typImpl.kind == nnkRefTy: typImpl[0][2] else: typImpl[2]
# Tuple should have exactly the same number of values as object
assert fields.len == data.len
# add fieldName: value to result for all fields/values
for i in 0..<fields.len:
result.add newTree(nnkExprColonExpr, fields[i][0], data[i])
# Result would be something like MyObj(x: 5, y: 7.0)
type MyObj = ref object
x: int
y: float
let myObj = createObj(MyObj, (5, 7.0))
echo myObj.y
