Parsing nodes on JSON with Scala - -

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i've been asked parse json file buses on specified speed inputed user.

the json file can downloaded here

it's this: 

{ "columns": [     "datahora",     "ordem",     "linha",     "latitude",     "longitude",     "velocidade" ], "data": [     [         "04-16-2015 00:00:55",         "b63099",         "",         -22.7931,         -43.2943,         0     ],     [         "04-16-2015 00:01:02",         "c44503",         781,         -22.853649,         -43.37616,         25     ],     [         "04-16-2015 00:11:40",         "b63067",         "",         -22.7925,         -43.2945,         0     ], ] }

the thing is: i'm new scala , have never worked json before (shame on me). need "ordem", "linha" , "velocidade" data node.

i created case class enclousure data later on specified speed.

case class bus(ordem: string, linha: int, velocidade: int)

i did reading file textfile , spliting. although way, need foreknow content of file in order go lines after data node.

i want know how using json parser. i've tried many solutions, couldn't adapt problem, because need extract lines data node instead of nodes inside 1 node.

can me?

ps: sorry english, not native speaker.

first of all, need understand different json data types. basic types in json numbers, strings, booleans, arrays, , objects. data returned in example object 2 keys: columns , data. columns key has value array of strings , numbers. data key has value array of arrays of strings.

you can use library playjson work type of data:

val js = json.parse(x).as[jsobject] val keys = (js \ "columns").as[list[string]] val values = (js \ "data").as[list[list[jsvalue]]]  val busses = values.map(valuelist => {     val keyvalues = (keys zip valuelist).tomap      {       ordem <- keyvalues("ordem").asopt[string]       linha <- keyvalues("linha").asopt[int]       velocidade <- keyvalues("velocidade").asopt[int]     } yield bus(ordem, linha, velocidade) })

note use of asopt when converting properties expected types. operator converts key-values provided type if possible (wrapped in some), , returns none otherwise. so, if want provide default value instead of ignoring other results, use keyvalues("linha").asopt[int].getorelse(0), example.

you can read more play json methods used here, \ , as, , asopt in their docs.


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