How to export slots and accessors from Lisp classes?

Question

This is my class's package: ``` (in-package :cl-user) (defpackage foo (:use :cl) (:export :bar)) (in-package :foo) (defclass bar () (baz)) ``` I can create an instance of `bar` in package `cl-user`. ``` CL-USER> (defvar f) F CL-USER> (setf f (make-instance 'foo:bar)) # ``` But I can't access the member `baz`. Calling `slot-value` like so ... ``` CL-USER> (slot-value f 'baz) ``` ... results in this error message: ``` When attempting to read the slot's value (slot-value), the slot BAZ is missing from the object #. [Condition of type SIMPLE-ERROR] ``` I already tried to add `baz` to the `:export` list but that does not work either. How to export slots and accessors from packages?

Accepted Answer

You can't export slots and accessors.

In Common Lisp you can export symbols.

So, export the symbol `BAZ` which names the slot.

Then in package `CL-USER`:

```
(slot-value some-instance 'foo:baz)
```

Unexported you have to write:

```
(slot-value some-instance 'foo::baz)
```

If you import the symbol into the package `CL-USER`:

```
(slot-value some-instance 'baz)
```

How to export slots and accessors from Lisp classes?

Solution

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