Write a prettyPrinted JSON object with sorted keys in Swift

Question

We often want to use JSON for human readability. As such, it is common to ask to sort the JSON keys alphabetically (or alphanumerically) in Go, in .NET, in Python, in Java, ...<

Answer 1

Here is one possible workaround that works only for macOS Swift scripts. It is not for iOS.

We workaround Swift Foundation limitations with a different programming language (Python 2.7 for example).

import Cocoa

// sample jsonObject
let jsonObject = ["hello": "world", "foo": "bar"]

// writing JSON to file
let jsonPath = "myJson.json"
let outputJSON = OutputStream(toFileAtPath: jsonPath, append: false)!
outputJSON.open()
_ = JSONSerialization.writeJSONObject(jsonObject, to: outputJSON, options: [], error: nil)
outputJSON.close()

// sortedKeys equivalent using `sort_keys=True`
// prettyPrinted equivalent using `indent=2, separators=(',', ' : ')`
// unicode using `io.open` and `ensure_ascii=False`
func shell(_ args: String...) {
    let task = Process()
    task.launchPath = "/usr/bin/env"
    task.arguments = args
    task.launch()
    task.waitUntilExit()
}
shell("python", "-c", ""
    + "import io\n"
    + "import json\n"
    + "jsonPath = 'myJson.json'\n"
    + "with io.open(jsonPath, mode='r', encoding='utf8') as json_file:\n"
    + "    all_data = json.load(json_file)\n"
    + "with io.open(jsonPath, mode='w', encoding='utf8') as json_file:\n"
    + "    json_file.write(unicode(json.dumps(all_data, ensure_ascii=False, sort_keys=True, indent=2, separators=(',', ' : '))))\n"
)