scala macro annotation 使用 例子

功能:用 宏注解实现一个 为case class 生成get set 方法 注解

github 地址:https://github.com/1178615156/use-scala-macro-annotation-make-get-set

//功能如下

@MakeGetSetcase class Hello(                  var a: String,                  var int: Int,                  var option: Option[String],                  var none: Option[AnyRef] = None,                  val hello: Boolean = true                  )object Main {  def main(args: Array[String]) {    val a = new Hello("a", 1, Some("option"))    //a.a    println(a.getA)//a    //a.int    println(a.getInt)//1    //return option.getOrElse(null)    println(a.getOption)//option    //return option.getOrElse(null)    println(a.getNone)//null    //a.none=Option(Some(""))    a.setNone(Some(""))    println(a.none)//Some(Some())    //a.none=Some("")    a.none = Some("")    println(a.none)//Some()    println(a.getHello)//true    //no have this method because hello is val    //a.setHello(false )  }}

宏 的实现代码 :

import scala.reflect.macros.blackbox.Contextimport scala.language.experimental.macrosimport scala.annotation.{compileTimeOnly, StaticAnnotation}/** * Created by YuJieShui on 2015/9/4. */@compileTimeOnly("")class MakeGetSet extends StaticAnnotation {  def macroTransform(annottees: Any*): Any = macro AnnotationGetSetMacroImpl.impl}class AnnotationGetSetMacroImpl(val c: Context) {  import c.universe._  //get case class  def getInCaseClass(list_annottees: List[Tree]) = list_annottees match {    case caseClass :: Nil => caseClass    case caseClass :: companionObject :: Nil => caseClass  }  def impl(annottees: c.Expr[Any]*): c.Expr[Any] = {    val inCaseClass = getInCaseClass(annottees.map(_.tree).toList)    val out: c.universe.Tree = inCaseClass match {      //if inCaseClass no a case class      //throw match error      case q"case class $name(..$params) extends ..$bases { ..$body }" =>        val list_params: List[ValDef] = params.asInstanceOf[List[ValDef]]        val get_set_params_func = list_params.map((param: c.universe.ValDef) => {          //get method name          val get_name = TermName("get" + {            val vn = param.name.toString;            vn.head.toString.toUpperCase() + vn.tail          })          //set method name          val set_name = TermName("set" + {            val vn = param.name.toString;            vn.head.toString.toUpperCase() + vn.tail          })          param match {            case ValDef(mods: Modifiers, name: TermName, tpt: Tree, rhs: Tree) =>              val v_type: c.universe.Tree = tq"$tpt"              //如果参数类型为泛型参数              v_type.children.headOption.map {                // where type is Option[_]                case tq"Option" =>                  Tuple2(                    q"""@..${mods.annotations}                        def $get_name = $name.orNull                        """,                    //where value is var                    //make set method                    if (mods.hasFlag(Flag.MUTABLE))                      q"def $set_name(sss:${v_type.children(1)}):Unit=this.${name}=Option(sss)"                    else                      q""                  )                //other such : Future[_],List[_]                case _ =>                  Tuple2(                    q"def $get_name = ${param.name}",                    q""                  )              } //非泛型参数                .getOrElse(Tuple2(                q"def $get_name= {${param.name}}",                if (mods.hasFlag(Flag.MUTABLE))                  q"def $set_name(sss:$v_type):Unit=this.${name}=sss"                else                  q""              ))          }        }).flatMap(t2 => List(t2._1, t2._2))        q"""            case class $name(..$params) extends ..$bases {            ..$get_set_params_func            ..$body            }            """    }    c.Expr(out)  }}