Nim Table is not updated - nim-lang

Question

I'm pretty new to Nim.
I have this code:
type
Environment* = object
values*: Table[string, BaseType]
error*: Error
proc newEnv*(errorObj: Error): Environment =
return Environment(
values: initTable[string, BaseType](),
error: errorObj
)
proc define*(env: var Environment, name: string, value: BaseType) =
env.values[name] = value
echo(env.values)
proc get*(env: var Environment, name: Token): BaseType =
echo(env.values)
if env.values.hasKey(name.value):
return env.values[name.value]
else:
# do something...
type Interpreter* = object
error*: Error
env*: Environment
proc newInterpreter*(errorObj: Error): Interpreter =
return Interpreter(
error: errorObj,
env: newEnv(errorObj)
)
method eval*(self: var Interpreter, expre: Expr): BaseType {.base.} = discard
method eval*(self: var Interpreter, statement: Stmt) {.base.} = discard
method eval*(self: var Interpreter, expre: VariableExpr): BaseType =
return self.env.get(expre.name)
method eval*(self: var Interpreter, statement: VariableStmt) =
var value: BaseType
if not statement.init.isNil: value = self.eval(statement.init)
self.env.define(statement.name.value, value)
As you can see, when eval proc with VariableStmt is called, it calls define proc to bind the name with the value.
However, the two echo statements print this:
{"a": 123}
{:}
The first line is from define proc, and the second line is from get proc.
Even though it looks like "a" and 123 got saved from calling define proc, inside get proc, the values table is empty.
I am not sure why this is. Could you help me solve this?
I will provide more information if you need it.
Update
I put an echo statement just before return self.env.get(expre.name), and it prints out this:
(data: #[(hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil), (hcode: 0, key: "", val: nil)], counter: 0)
I'm not sure what this is. Is it a bug of Nim?

Answer 1

I tried to boil this down to a minimal working sample (always a good strategy when trying to track down a bug or get help). However this works:
import tables
type
Environment = object
table: Table[string, string]
Interpreter = object
env: Environment
proc define(env: var Environment, name, key: string) =
env.table[name] = key
echo env.table
proc get(env: var Environment, name: string): string =
echo env.table
env.table.getOrDefault(name, "")
proc eval(self: var Interpreter, command, name: string, value = "") =
if command == "ADD":
self.env.define(name, value)
elif command == "GET":
echo self.env.get(name)
var interpreter: Interpreter
interpreter.eval("ADD", "hello", "world")
interpreter.eval("GET", "hello")
This leads me to believe that you somewhere manage to make a copy of your interpreter or the environment as you pass it around. An easy mistake to make, but hard to tell where you made it or if it even is that without a more complete code sample (preferably something which runs of course).
EDIT: By the way, you probably don't need methods. You might, but it's quite a common beginner mistake to use them when you don't.