zadr/ j2s
About the developer
210 Stars 
14 Forks 
Other 
67 Commits 
6 Opened issues 
Description
A macOS app to convert JSON to Swift structs
Services available
Contributors list
What's this?
j2sis a macOS app that converts
JSONdictionaries into Swift
structs.
That's it? Can I make it do anything else?
No, yeah, that's it. You give
j2sa
jsonfile, and it gives you Swift
structs. You can pick if it outputs to one file or a n files for n
structs.
If you want to make it do anything else, you'll have to write some more code. I'll probably accept pull requests, but, you should probably look into other tools like Sourcery instead.
Codable-compliant struct
s, right?
Yup.
Cool
Yeah.
j2swill also convert
snake_case_key_namesinto
camelCasePropertyNames, and if you have a key where the value is an array of of dictionaries, the key name will be — naively — depluralized (exact line of code may change, but look around there for the algorithm).
And, if your
JSONvalue is a string that's secretly a
Datein a format that
j2sunderstands (Currently:
ISO8601), the generated code will use the correct (
Date) type.
Also, an integer like
5is an
Intand a floating point number like
5.0is a
Double. Because, you know, thats how these things should work.
What version of Swift does this target?
j2s.xcodeprojrequires Swift 4 (Xcode 9 or greater) to build. The code it outputs requires Swift 4. If you need Swift 3 support, try looking back in commit history for an older version.
What's the generated code look like?
j2scan take in the following
JSON:
{
"outer" : true,
"nested" : {
"what_if_i_want_to" : [
"boogie? wouldn't dream of stopping you"
],
"when" : "2017-06-27T17:58:28+00:00",
"cool" : true
}
}
and turn it into Swift code that looks like this:
public struct Root: Codable {
public let nested: Nested
public let outer: Bool
public struct Nested: Codable {
public let cool: Bool
public let whatIfIWantTo: [String]
public let when: Date
private enum CodingKeys: String, CodingKey {
case cool
case whatIfIWantTo = "what_if_i_want_to"
case when
}
}
}
// MARK: -
public extension Root {
static func create(with data: Data) throws -> Root {
return try JSONDecoder().decode(Root.self, from: data)
}
static func create(with data: Data) throws -> [Root] {
return try JSONDecoder().decode([Root].self, from: data)
}
}
// MARK: -
public extension Root.Nested {
static func create(with data: Data) throws -> Root.Nested {
let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .iso8601
return try decoder.decode(Root.Nested.self, from: data)
}
static func create(with data: Data) throws -> [Root.Nested] {
let decoder = JSONDecoder()
decoder.dateDecodingStrategy = .iso8601
return try decoder.decode([Root.Nested].self, from: data)
}
}
What about Optional
s? I heard Swift has Optional
s, but, I don't see any Optional
s.
Optionals are sort of handled by
j2s.
JSONdoesn't have
Optionals, so it's hard to map them over automatically.
While parsing, if
j2sis told to create the same
structmultiple times, it considers any properties that don't exist in both models to be
Optional.
The same is also true for properties that show up as
nulland as a
Type.
nulls are turned into
Any?.
Oh.
Yeah. Usually happens in the case of an array of dictionaries. This
JSON:
{
"outer" : true,
"nested" : {
"im_going_to_" : [
"type? sure, but uncheck the \"Pretty-Print JSON\" box down there --v",
"boogie? wouldn't dream of stopping you"
],
"what" : "paste json here"
}
}
will generate this Swift code:
public struct Demo: Codable {
public let nested: Nested
public let outer: Bool
public struct Nested: Codable {
public let imGoingTo: [String]
public let what: String
private enum CodingKeys: String, CodingKey {
case im_going_to_ = "imGoingTo"
case what
}
}
private enum CodingKeys: String, CodingKey {
case nested
case outer
}
}
// MARK: -
public extension Nested {
public static func create(with data: Data) throws -> Nested {
return try JSONDecoder().decode(Nested.self, from: data)
}
public static func create(with data: Data) throws -> [Nested] {
return try JSONDecoder().decode([Nested].self, from: data)
}
}
// MARK: -
public extension Demo {
public static func create(with data: Data) throws -> Demo {
return try JSONDecoder().decode(Demo.self, from: data)
}
public static func create(with data: Data) throws -> [Demo] {
return try JSONDecoder().decode([Demo].self, from: data)
}
}
Why build this and not use some other tool?
Seemed like a good idea. This was before
Codablewas a thing.
Still hung up on depluralization? (Singularity?)
A
JSONdictionary with a key named
potatoes, where the value is a list of dictionaries will be given the Swift type
[Potato]. Similarly,
soliloquiesbecomes
[Soliloquy],
dwarvesand
[Dwarf], and so on. Depluralization is a giant
ifstatement though, so while
indicesbecomes
[Index],
matricesincorrectly becomes
matrex. If Anyone wanted to do some natural language processing to solve this, that would be cool.
Okay then
Before you go, remember that
j2scode is released under a 2-Clause BSD License and all contributions and project activity should be in line with our Code of Conduct.