stew/objects: add baseType()

README.md

@@ -24,6 +24,7 @@ respective folders
 - `bitops2` - an updated version of `bitops.nim`, filling in gaps in original code
 - `byteutils` - utilities that make working with the Nim `byte` type convenient
 - `endians2` - utilities for converting to and from little / big endian integers
+- `objects` - get an object's base type at runtime, as a string
 - `ptrops` - pointer arithmetic utilities
 - `ranges` - utility functions for working with parts and blobs of memory
 - `shims` - backports of nim `devel` code to the stable version that Status is using

stew.nimble

@@ -11,4 +11,4 @@ requires "nim >= 0.19.0"
 
 task test, "Run all tests":
   exec "nim c -r --threads:off tests/all_tests"
-  exec "nim c -r --threads:on tests/all_tests"
+  exec "nim c -r --threads:on -d:nimTypeNames tests/all_tests"

stew/objects.nim

@@ -31,3 +31,15 @@ when not compiles(len((1, 2))):
   func len*(x: tuple): int =
     arity(type(x))
 
+# Get an object's base type, as a cstring. Ref objects will have an ":ObjectType"
+# suffix.
+# From: https://gist.github.com/stefantalpalaru/82dc71bb547d6f9178b916e3ed5b527d
+proc baseType*(obj: RootObj): cstring =
+  when not defined(nimTypeNames):
+    raiseAssert("you need to compile this with '-d:nimTypeNames'")
+  else:
+    {.emit: "result = `obj`->m_type->name;".}
+
+proc baseType*(obj: ref RootObj): cstring =
+  obj[].baseType
+

tests/all_tests.nim

@@ -16,6 +16,7 @@ import
   test_bitseqs,
   test_byteutils,
   test_endians2,
+  test_objects,
   test_ptrops,
   test_result,
   test_varints

tests/test_objects.nim

@@ -0,0 +1,36 @@
+import unittest,
+  ../stew/objects
+
+when defined(nimHasUsed):
+  {.used.}
+
+suite "Objects":
+  test "baseType":
+    type
+      Foo = ref object of RootObj
+      Bar = ref object of Foo
+      Baz = object of RootObj
+      Bob = object of Baz
+      Bill = ref object of Bob
+
+    var
+      foo = Foo()
+      bar = Bar()
+      baz = Baz()
+      bob = Bob()
+      bill = Bill()
+
+    when defined(nimTypeNames):
+      check:
+        foo.baseType == "Foo:ObjectType"
+        bar.baseType == "Bar:ObjectType"
+        baz.baseType == "Baz"
+        bob.baseType == "Bob"
+        bill.baseType == "Bill:ObjectType"
+
+      proc f(o: Foo) =
+        check $o.type == "Foo"
+        check o.baseType == "Bar:ObjectType"
+
+      f(bar)
+