Scala Json-Json列表

Question

I have the below code and the output from my program. However, I could not create a List of Json (desired output) given below. What kind changes do I need to do in the existing code?

case class Uiresult(AccountNo: String, Name: String)

val json = parse(jsonString)
val elements = (json \\ "_source").children
for (acct <- elements) {
  val m = acct.extract[Source]
  val res = write(Uiresult(m.accountNo, (m.firstName + m.lastName))
  println(res)
}

Output from current program:

{"AccountNo":"1234","Name":"Augustin John"}
{"AccountNo":"1235","Name":"Juliet Paul"}
{"AccountNo":"1236","Name":"Sebastin Arul"}

Desired output:

[
{"AccountNo":"1234","Name":"Augustin John"},
{"AccountNo":"1235","Name":"Juliet Paul"},
{"AccountNo":"1236","Name":"Sebastin Arul"}
]

Answer 1

To create a list for the for comprehension, use the yield keyword. This will return the values from the iterations and create a list for you, which you then can assign to a val .

val list = for (acct <- elements) yield {
  val m = acct.extract[Source]
  val res = write(Uiresult(m.accountNo, (m.firstName + m.lastName))
  res
}

This can be written even shorter,

val list = for (acct <- elements) yield {
  val m = acct.extract[Source]
  write(Uiresult(m.accountNo, (m.firstName + m.lastName))
}

The type of list ( Array , List , Seq , etc.) will be determined by the type of elements . Other data structures such as set dictionaries are also possible to use in this way.

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To print the output into the exact format as in the "desired output" above, use mkString .

println(list.mkString("[\n", ",\n", "\n]"))