这就是我想要的:
scala> var x:Int = 10
x: Int = 10
scala> var y:Int = 20
y: Int = 20
scala> val ret = q"return $x>$y"
ret: universe.Return = return 10.$greater(20)
scala> val result1 = toolbox.compile(ret)()
result1: Any = false
但问题是我将在字符串var中得到表达式$ x> $ y,例如
scala> m
res20: String = $x>$y
然后我想执行操作,
var ret = q"return $m"
但这回归:
scala> var ret = q"return $m"
ret: universe.Return = return "$x>$y"
不符合此目的。如何在最后一步获得x和y的值,而不是 $ x和$ y。
答案 0 :(得分:0)
你可以混合使用quasiquotes和ToolBox.parse
来达到你想要的结果:
import scala.tools.reflect.ToolBox
import scala.reflect.runtime.universe._
val toolbox = scala.reflect.runtime.currentMirror.mkToolBox()
val s = "10>20"
val ret = q"return ${toolbox.parse(s)}"
// reflect.runtime.universe.Return = return 10.$greater(20)
toolbox.eval(ret)
// Any = false
将您的值用作变量:
import scala.tools.reflect.ToolBox
import scala.reflect.runtime.universe._
val toolbox = scala.reflect.runtime.currentMirror.mkToolBox()
val x = 10
val y = 20
val m = "x>y"
val ret = q"return ${toolbox.parse(m)}"
// reflect.runtime.universe.Return = return x.$greater(y)
如果您评估q"return ${toolbox.parse(m)}"
,则会看到错误,因为x
和y
不在范围内。
scala> toolbox.eval(q"return ${toolbox.parse(m)}")
scala.tools.reflect.ToolBoxError: reflective compilation has failed:
object > is not a member of package x ...
解决这个问题:
import scala.tools.reflect.ToolBox
import scala.reflect.runtime.universe._
val toolbox = scala.reflect.runtime.currentMirror.mkToolBox()
val q1 = q"val x = 10; val y = 20; "
val m = "x>y"
val ret = q"""
| ..$q1
| return ${toolbox.parse(m)}
| """
toolbox.eval(ret)
// Any = false