正确使用浮油过滤器 [英] right usage of slick filter

问题描述

我正在使用Slick来访问数据库.我想这样查询:

I'm using slick to access database. I want to query like this:

case class Coupon(couponId: Long, shopId: String)

class Coupons(tag: Tag) extends Table[Coupon](tag, "coupons"){

  def couponId = column[Long]("coupon_id")

  def shopId = column[String]("shop_id")

  override def * = (couponId, shopId) <> (Coupon.tupled, Coupon.unapply)
}

object Coupons extends TableQuery(new Coupons(_)){

  def findCouponBy(couponId: Long, shopId: Option[String]) = {

    val s = DB.createSession()
    try {
       val q = for {
           coupon <- this.filter(c => c.couponId === couponId && 
                shopId.map(s => c.shopId === s).getOrElse(true)
        } yield coupon
      s.database.run(q.result)
    } finally s.close
  }
}

我认为这可能有效.但是，编译器告诉我 错误:(126，-1)播放2编译器: 类型不匹配; 找到:任何 必需:slick.lifted.Rep [?]

I thought this might work. However, the compiler tells me that Error:(126, -1) Play 2 Compiler: type mismatch; found : Any required: slick.lifted.Rep[?]

问题就在这里: shopId.map(s => c.shopId === s).getOrElse(true)

Problem lies on here: shopId.map(s => c.shopId === s).getOrElse(true)

我想知道如何进行这项工作.

I'm wondering how I can make this work.

我正在使用光滑的3.0.0-RC

I'm using slick 3.0.0-RC

推荐答案

使用slick.lifted.LiteralColumn(true)

Scala的类型推断限制

Scala's type infer limitation

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