Examples

The dynamic API and the generated API write the same Ion. Use the dynamic API when the shape is not known ahead of time. Use a generated struct when a schema already names the fields.

Dynamic document

examples/main.swift decodes one struct and writes it twice. Run it with swift run encode-value.

import Ion

let cat = Catalog()
let doc = try decode(Array("{a:1,b:\"hi\"}\n".utf8), cat)
let text = try encode(doc, EncodeOptions(binary: false, pretty: false, version: 10), cat)
let binary = try encode(doc, EncodeOptions(binary: true, pretty: false, version: 11), cat)
print("text bytes", text.count)
print("ion 1.1 binary bytes", binary.count)

Ion 1.0 text starts with $ion_1_0. Ion 1.1 binary starts with E0 01 01 EA and stores the field name a as inline symbol text, so the stream has no symbol table.

Build a value without parsing

import Ion

let doc = IonDoc()
let st = doc.startContainer(kStruct)
let field = doc.addSymbolText("n")
doc.addChild(st, doc.addI64(150), doc.nodes[field].a)
doc.addTop(st)

kStruct is the struct kind. addI64 accepts any Int64. Wider integers go through addInt and a BigInt. addDecimal keeps the coefficient and the exponent, including a negative zero. addTime keeps precision and offset.

Generated struct

testdata/schema/message.json describes a closed object. After bash scripts/generate.sh, tests/generated/Message.swift has the fields below.

Schema field	Swift field	Required
id	Int64	yes
name	String	yes
ok	Bool	no
weight	Double	no
tags	[String]	no
when	String holding Ion timestamp text	no
payload	[UInt8]	no

var msg = Message()
msg.id = 7
msg.name = "ada"
msg.has_when = true
msg.when = "2023T"
var buf: [UInt8] = []
try msg.encode(to: &buf, EncodeOptions(binary: true, pretty: false, version: 10))
let back = try Message.decode(from: buf)

Optional fields use a has_ flag. A missing flag omits the field. A closed schema raises DecodeError.kindSchema when a required field is absent or an unknown field is present.

testdata/schema/point.ion is Ion Schema. label is a symbol, so the generated String holds Ion symbol text such as foo, not a quoted string. encode with version 11 writes an Ion 1.1 binary struct.