我有一類情況是這樣的:非隱含寫入不能與期權交易(斯卡拉,JSON,播放2.3.6)
case class Product(ean: Long, name: String, description: String, purchasePrice: Option[BigDecimal] = None, sellingPrice: Option[BigDecimal] = None)
而且我有一個這樣的非隱寫道:
val adminProductWrites = (
(JsPath \ "ean").write[Long] and
(JsPath \ "name").write[String] and
(JsPath \ "description").write[String] and
(JsPath \ "purchase_price").writeNullable[BigDecimal] and
(JsPath \ "selling_price").writeNullable[BigDecimal]
)(unlift(Product.unapply))
然後,我有選擇的實例[產品]:
val prod = Some(Product(5018206244611L, "Zebra Paperclips", "Zebra Length 28mm Assorted 150 Pack"))
當我試圖連載吧...:
val jsonStr = Json.toJson(prod) (adminProductWrites)
我得到了這樣的錯誤:
<console>:21: error: type mismatch;
found : play.api.libs.json.OWrites[Product]
required: play.api.libs.json.Writes[Some[Product]]
val jsonStr = Json.toJson(prod) (adminProductWrites)
所以,第一個(只作比較)我嘗試這樣做:
val jsonStr = Json.toJson(prod.get) (adminProductWrites)
它的工作原理:
jsonStr: play.api.libs.json.JsValue = {"ean":5018206244611,"name":"Zebra Paperclips","description":"Zebra Length 28mm Assorted 150 Pack"}
但我不想那樣做(調用.get)。我需要工作時寫操作被聲明爲隱它的方式:
implicit object ProductWrites extends Writes[Product] {
def writes(p: Product) = Json.obj(
"ean" -> Json.toJson(p.ean),
"name" -> Json.toJson(p.name),
"description" -> Json.toJson(p.description)
)
}
(有內隱寫道,該行工作):
scala> val jsonStr = Json.toJson(prod)
jsonStr: play.api.libs.json.JsValue = {"ean":5018206244611,"name":"Zebra Paperclips","description":"Zebra Length 28mm Assorted 150 Pack"}
我缺少什麼?
附加說明:
我的隱寫操作是不完整的,我特意去掉最後2場(進價和sellingPrice)。原因:此代碼不能編譯:
implicit object ProductWrites extends Writes[Product] {
def writes(p: Product) = Json.obj(
"ean" -> Json.toJson(p.ean),
"name" -> Json.toJson(p.name),
"description" -> Json.toJson(p.description),
"purchase_price" -> p.purchasePrice.getOrElse(None),
"selling_price" -> p.sellingPrice.getOrElse(None)
)
}
我給出了這樣的錯誤:
<console>:24: error: No Json serializer found for type Serializable. Try to implement an implicit Writes or Format for this type.
"purchase_price" -> Json.toJson(p.purchasePrice.getOrElse(None)),
由於提前, 拉嘎
我發現了類似/相關問題,沒有蓋棺定論的答案: HTTP://計算器。com/questions/25867579/play-2-3-scala-explicit-passing-writer-needs-to-match-optiont-vs-t-impli – 2014-10-28 04:49:42
我已經搜遍了所有東西,並嘗試了幾件事情,看起來像。 ..這是Play 2.3.6(?)中的一個錯誤。因此,在此期間 - 直到它被修復 - 我們必須與隱式作家(?)合作。 – 2014-10-28 05:23:27
在另一個網站上完全相同的問題,也沒有答案(尚未):http://grokbase.com/t/gg/play-framework/149g6gt03j/2-3-scala-explicitly-passing-writer-needs-to- match-option-t-vs-t-implicit-writer-can-handle-both – 2014-10-28 05:33:04