Lesson 27 · Serializing objects - Build a JSON Parser

Serializing objects

Objects are the last kind to serialize - key-value members joined by commas, with each key written as a quoted string. Today you complete the compact serializer.

The goal

Serialize an object value as a compact list of quoted-key, value members in stored order.

Start here - the target

TO DO

Scenario: Writing objects as text

Givenan object Value

WhenSerialize is called

Thenan empty object is "{}", and the object with members a then b holding Number 1 and 2 serializes to {"a":1,"b":2}

Andmembers keep their stored order and each key is escaped as a string, so a member key a with a Number 1 nested array value {"a":[1]} serializes to {"a":[1]}

Background

An object serializes like an array, with one twist per member: each member is a quoted key, a colon, and the serialized value. Reuse the string serializer from two lessons ago for the key so that keys needing escapes are handled correctly. Members are separated by commas, with no spaces around the colon or the comma in compact form, and the empty object is {}.

Crucially, emit members in their stored order - the order the parser preserved - rather than sorting or randomizing them. That makes serialization deterministic and, for a document that was parsed from canonical text, an exact inverse of parsing. With objects done, Serialize covers all six value kinds, and every value tree can now be written back to text. The next lesson proves it forms a clean round-trip.

Make it work

// object case of Serialize:
//   '{' + join(serializeString(m.Key)+":"+Serialize(m.Value), ",") + '}'
// reuse the string escaper for the key; no spaces around ':' or ','
// iterate members in their stored order

CheckpointDONE

The compact serializer is complete for every value kind. Commit and stop here.