json

The json module provides a mutable JSON tree with parsing and serialization.

use json

var j <- OJson()
j.AddStr("name", "dq")
j.AddNum("version", 1)
PrintLn("{}", [j.pretty_json])

Errors raise EJson.

Node Kinds

enum NJsonNodeKind = (nkNull, nkBool, nkNumber, nkString, nkObject, nkArray)

An OJson node stores its kind, optional scalar value, parent pointer, name, and children.

Building Trees

var root <- OJson()
root.AddStr("title", "example")
root.AddBool("ok", true)

var items : OJson = root.AddArr("items")
items.AddStr("", "first")
items.AddNum("", 2)

var cfg : OJson = root.ForcePath("settings/theme")
cfg.as_str = "dark"

Method	Meaning
AddNull(name)	append null child
AddBool(name, value)	append boolean child
AddStr(name, value)	append string child
AddNum(name, value)	append number child
AddObj(name)	append object child
AddArr(name)	append array child
Clear()	delete all children

For array items, the name is usually "".

Reading And Writing Values

Property / method	Meaning
.name	node name, or "0" for root
.parent	parent node
.as_str	read/write scalar as string
.as_num	read/write scalar as float
.as_bool	read/write scalar as bool
.is_null	true for JSON null
.json	compact JSON string
.pretty_json	indented JSON string
.length	child count
.child[index]	child by index, or null

var title : str = root.ChildByName("title").as_str

Finding Nodes

var jv : OJson

// most practical:
if root.Find("settings.theme", jv):
    PrintLn("theme={}", [jv.as_str])
endif

// traditional:
jv = root.FindNode("settings/theme")
if jv <> null:
    PrintLn("theme={}", [jv.as_str])
endif

Paths can use . or / between object names. ForcePath creates missing object nodes.

Parsing And Files

var j <- OJson()
j.Parse('{"answer":42}')
j.LoadFromFile("config.json")
j.SaveToFile("out.json", true)

The root JSON text must be an object or array. Strings support JSON escapes, including Unicode escapes and surrogate pairs.