Serializing/deserializing objects to/from JSON on Toit language

Question

I've a few questions about using json. I can see that there are corresponding modules in the attached library lib_v1.0.2, but the examples do not use them. Is it possible to give two simple examples: serializing an object into a json string and deserializing json into the same object: for example object's creation via constructor.json jsonString. If possible, in addition to serializing/deserializing ordinary fields: strings, int, bool, explain how to serialize/deserialize & hash maps & lists if object contains them.

Answer 1

Update: the encoder now takes a converter block which is invoked for objects it doesn't know how to serialize. The converter is supposed to convert that object into something the encoder understands.

Currently, the JSON library only supports a hardcoded list of types:

  encode obj:
    if obj is string: encode_string_ obj
    else if obj is num: encode_number_ obj
    else if identical obj true: encode_true_
    else if identical obj false: encode_false_
    else if identical obj null: encode_null_
    else if obj is Map: encode_map_ obj
    else if obj is List: encode_list_ obj
    else: throw "INVALID_JSON_OBJECT"

This means that it can't serialize/deserialize objects of other (user-defined) types.

I have filed a feature request here: https://github.com/toitware/public/issues/6

Answer 2

I haven't yet tested the deserialization of complex json objects, but apparently Toit supports serialization/deserialization of containers, includes nested ones. For example a list:

import encoding.json as json

main :
  list := [1,2,"covid-19",25,[11,12,"toit",13,14],{"fortran":[77,90]}]
  a1 := list[0]
  log("a1->$a1")
  a2 := list[1]
  log("a2->$a2")
  a3 := list[2]
  log("a3->$a3")
  a4 := list[3]
  log("a4->$a4")
  a5 := list[4]
  log("a5->$a5")
  a6 := list[5]
  log("a5->$a6")

  jsonObjList := json.encode list
  log("jsonObjList($list)")
  
  listClone := json.decode jsonObjList
  log("listClone->($list)")

  aa1 := listClone[0]
  log("aa1->$aa1")
  aa2 := listClone[1]
  log("aa2->$aa2")
  aa3 := listClone[2]
  log("aa3->$aa3")
  aa4 := listClone[3]
  log("aa4->$aa4")
  aa5 := listClone[4]
  log("aa5->$aa5")
  aa6 := listClone[5]
  log("aa5->$aa6")

  jsonObjListText := jsonObjList.to_string
  log("jsonObjListText-> $jsonObjListText")
  
  listClone2 := json.decode jsonObjListText.to_byte_array
  log("listClone2->($listClone2)")

  aaa1 := listClone2[0]
  log("aaa1->$aaa1")
  aaa2 := listClone2[1]
  log("aaa2->$aaa2")
  aaa3 := listClone2[2]
  log("aaa3->$aaa3")
  aaa4 := listClone2[3]
  log("aaa4->$aaa4")
  aaa5 := listClone2[4]
  log("aaa5->$aaa5")
  aaa6 := listClone2[5]
  log("aaa6->$aaa6")

Output:

michael_k@michaelk:~/toit_apps/json$ toit execute test_json.toit
a1->1
a2->2
a3->covid-19
a4->25
a5->[11, 12, toit, 13, 14]
a5->{fortran: [77, 90]}
jsonObjList([1, 2, covid-19, 25, [11, 12, toit, 13, 14], {fortran: [77, 90]}])
listClone->([1, 2, covid-19, 25, [11, 12, toit, 13, 14], {fortran: [77, 90]}])
aa1->1
aa2->2
aa3->covid-19
aa4->25
aa5->[11, 12, toit, 13, 14]
aa5->{fortran: [77, 90]}
jsonObjListText-> [1,2,"covid-19",25,[11,12,"toit",13,14],{"fortran":[77,90]}]
listClone2->([1, 2, covid-19, 25, [11, 12, toit, 13, 14], {fortran: [77, 90]}])
aaa1->1
aaa2->2
aaa3->covid-19
aaa4->25
aaa5->[11, 12, toit, 13, 14]
aaa6->{fortran: [77, 90]}
michael_k@michaelk:~/toit_apps/json$