Clojure Korma：如何在函数中使用where宏？

Question

我正在尝试在函数中使用where宏：

(defentity student
  (pk :id)
  (table :student)
  (entity-fields :id :name :age :class)
  (database prod))

(defn query-student [cond]
  (select student
    (where cond)))

我测试一下：

(select student
  (where {:age [> 13]}))

(query-student '{:age [> 13]})

看起来还可以，但这

(select student
  (where (or {:age [> 13]} {:class [in ["1" "2" "3"]]})))

(query-student '(or {:age [> 13]} {:class [in ["1" "2" "3"]]}))

不起作用！

Failure to execute query with SQL:
SELECT "student".* FROM "student" WHERE (or {:age [> 13]} {:class [in ["1" "2" "3"]]})  ::      []
PSQLException:
 Message: ERROR: syntax error at or near "or"
  Location：42
 SQLState: 42601
 Error Code: 0
PSQLException ERROR: syntax error at or near "or"
  Location：42  org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse  (QueryExecutorImpl.java:2101)

我想知道为什么吗？ 有问题？

Answer 1

在Korma中，宏在where ，因此您的第二个示例向其传递列表文字，而不是给宏提供评估表单的机会。

尝试按照以下步骤将您的query-student函数更改为宏

(defmacro query-student [cond]
  `(select student
    (where ~cond))) 

另外，使用宏时，您无需引用表格：

(query-student (or {:age [> 13]} {:class [in ["1" "2" "3"]]}))

希望这可以帮助。