Calling a string interpolator on a variable in Scala

问题

I am writing some database query helper methods for my classes in Scala.

This select method is intended to pluck certain columns from the Product table, specified as a comma-seperated list (String) of the desired columns.

I want to be able to call it like this: Product.select("id, title")

The following code does not work:

  def select(columns: String) = { DB.readOnly{ implicit session =>
    sql"select ${columns} from $sqlTable limit 1000".map(row => Product(row)).list.apply()
  }}

But this code (for illustration purposes only) does

  def select(columns: String) = { DB.readOnly{ implicit session =>
    var x = sqls"id, title, description, available_online"
    sql"select ${x} from $sqlTable limit 1000".map(row => Product(row)).list.apply()
  }}

Now, obviously I don't want to hard code columns into the method, but i want to do this with the columns parameter string (I hope you catch my drift). How can I apply the sqls interpolator on the columns string?

It would be something like var x = sqls(columns)

Here you can find more info on the sqls and sql interpolators

Please comment if you require more information and I'd appreciate your feedback.

回答1:

You can use SQLSyntax#createUnsafely instead.

https://github.com/scalikejdbc/scalikejdbc/blob/2.2.0/scalikejdbc-core/src/main/scala/scalikejdbc/interpolation/SQLSyntax.scala#L220

This is a dangerous API. I know you're aware of SQL injection vulnerability so much.

回答2:

Check class SQLSyntax. It could be used for your purposes. "sqls" is syntax sugar for SQLSyntax

def select(columns: String) = { DB.readOnly{ implicit session =>
var x = SQLSyntax("id, title, description, available_online", Seq.empty)
sql"select ${x} from $sqlTable limit 1000".map(row => Product(row)).list.apply()}}

If you interest deeply, see at class SQLInterpolationString

来源：https://stackoverflow.com/questions/26888933/calling-a-string-interpolator-on-a-variable-in-scala

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