play framework Reads[A] and, andThen, reduce

新手莫入(看完官方文件+自行實驗 心得)

and, reduce

會忽略沒有定義JsPath的tuple

最终有寫Reads的tuple才會留下

同常用於你想把Json減肥,或是挑選你要的tuple

 

Reads[A] andThen Reads[A] 並沒有忽略任何tuple

通常用於修改Json的內容, 但是tuple沒有減少

 

官方說法(看攏沒,WTF)

(Reads[JsObject] and Reads[JsObject]) reduce

• It merges results of both Reads[JsObject] (JsObject ++ JsObject)
• It also applies the same JSON to both Reads[JsObject] unlike andThen which injects the result of the first reads into second one.

andThen

• is just the composition of 2 Reads[A]
• first reads is applied and then result is piped to second reads

 

學習來源 Json transformers