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DESCRIPTION.md

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Description

What this module provides

  • The SION Type which can store and manipulate SION data.
  • conversion between

Initialization

You can build SION directly as a literal.

var sion:SION = [
    "nil":      nil,
    "bool":     true,
    "int":      -42,
    "double":   42.195,
    "string":   "漢字、カタカナ、ひらがなの入ったstring😇",
    "array":    [nil, true, 1, 1.0, "one", [1], ["one":1.0]],
    "dictionary":   [
        "nil":nil, "bool":false, "int":0, "double":0.0, "string":"","array":[], "object":[:]
    ],
    "url":"https://github.com/dankogai/"
]
sion["data"] = .Data("R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7")
sion["date"] = .Date(0.0)
sion["ext"]  = .Ext("1NTU")

limitation

Note that the RHS of the expression below is not exactly nil or true or -42. They are SION.Nil and SION.Bool(-42) and SION.Int(-42) respectively. That is why .Data and .Date are added later. Swift gets confused when you say

var sion:SION = [
    "string": "漢字、カタカナ、ひらがなの入ったstring😇",
    "data": .Data("R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7"),
]

Because it cannot tell they type of the content in. "". In which case you can explicitly say

var sion:SION = [
    "string": .String("漢字、カタカナ、ひらがなの入ったstring😇"),
    "data": .Data("R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7"),
]

or add "data" later.

from String

SION(string:"""
[
    "array": [
        nil,
        true,
        1,      // Int
        1.0,    // Double
        "one",
        [1],
        ["one" : 1.0]
    ],
    "bool": true,
    "data": .Data("R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7"),
    "date": .Date(0x0p+0),
    "dictionary": [
        "array" : [],
        "bool" : false,
        "double" : 0x0p+0,
        "int" : 0,
        "nil" : nil,
        "object" : [:],
        "string" : ""
    ],
    "double": 0x1.518f5c28f5c29p+5, // double in hex
    "ext": .Ext("1NTU"),            // 0xd4,0xd4,0xd4
    "int": -42,                     // int in hex
    "nil": nil,
    "string": "漢字、カタカナ、ひらがなの入ったstring😇",
    "url": "https://github.com/dankogai/"
]
""")

from JSON string or JSON-emitting URL

SION(jsonString:"""
{
    "array" : [
    null,
    true,
    1,
    1.0,
    "one",
    [
      1
    ],
    {
      "one" : 1.0
    }
    ],
    "bool" : true,
    "dictionary" : {
        "array" : [],
        "bool" : false,
        "double" : 0.0,
        "int" : 0,
        "nil" : null,
        "object" : {},
        "string" : ""
    },
    "double" : 42.195,
    "int" : -42,
    "nil" : null,
    "string" : "漢字、カタカナ、ひらがなの入ったstring😇",
    "url" : "https://github.com/dankogai/"
}
""")
SION(jsonUrlString:"https://api.github.com")

from Property List

let plistXML = """
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
  <key>array</key>
  <array>
    <true/>
    <integer>1</integer>
    <real>1</real>
    <string>one</string>
    <array>
      <integer>1</integer>
    </array>
    <dict>
      <key>one</key>
      <real>1</real>
    </dict>
  </array>
  <key>bool</key>
  <true/>
  <key>data</key>
  <data>
    R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7
  </data>
  <key>date</key>
  <date>1970-01-01T00:00:00Z</date>
  <key>dictionary</key>
  <dict>
    <key>array</key>
    <array/>
    <key>bool</key>
    <false/>
    <key>double</key>
    <real>0.0</real>
    <key>int</key>
    <integer>0</integer>
    <key>object</key>
    <dict/>
    <key>string</key>
    <string></string>
  </dict>
  <key>double</key>
  <real>42.195</real>
  <key>int</key>
  <integer>-42</integer>
  <key>string</key>
  <string>漢字、カタカナ、ひらがなの入ったstring😇</string>
  <key>url</key>
  <string>https://github.com/dankogai/</string>
</dict>
</plist>
"""
SION(propertyList:plistXML.data(using:.utf8)!, format:.xml)

from msgPack

import Foundation
SION(msgPack: Data([
    0x82,0xa7,0x63,0x6f,0x6d,0x70,0x61,0x63,
    0x74,0xc3,0xa6,0x73,0x63,0x68,0x65,0x6d,
    0x61,0x00
]))   // ["compact":true,"schema":0]

Conversion

once you have the SION object, converting to other formats is simple.

to SION string, all you need is stringify it. .description or "\(json)" should be enough.

sion.description
"\(sion)"				// SION is CustomStringConvertible

If you need JSON, simply call .json.

sion.json

And .msgPack gives you msgPack in Data.

sion.msgPack

limitation

Since JSON does not support Date and Data, .json converts Date to Number and Date to Base64-encoded String respectively. .json also coverts all non-String keys to String. Do not expect JSON to round trip. It is less expressive than SION.

You can also get YAML via .yaml.

sion.yaml

And .propertyList for Property List.

// pick() removes Nil
String(data:try! sion.pick{ !$0.isNil }.propertyList(format: .xml), encoding:.utf8)!

Manipulation

a blank SION Array is as simple as:

var sion = SION([])

and you can assign elements like an ordinary array

sion[0] = nil
sion[1] = true
sion[2] = 1

note RHS literals are NOT nil, true and 1 but .Null, .Bool(true) and .Number(1). Therefore this does NOT work

let one = "one"
sion[3] = one // error: cannot assign value of type 'String' to type 'SION'

In which case you do this instead.

sion[3].string = one

They are all getters and setters…

sion[1].bool       = true
sion[2].int        = 1
sion[3].double     = 1.0
sion[4].string     = "one"
sion[5].array      = [1]
sion[6].dictionary = ["one":1]

except for .number which is a getter-only property that retrieves numerical value in Double or nil if not numeric.

swift[1].number   // nil
swift[2].number!  // 1.0 - Int is cast to Double
swift[3].number!  // 1.0

As a getter they are optional which returns nil when the type mismaches.

sion[1].bool    // Optional(true)
sion[1].int     // nil

Therefore, you can mutate like so:

sion[2].int! += 1               // now 2
sion[3].double! *= 0.5          // now 0.5
sion[4].string!.removeLast()    // now "on"
sion[5].array!.append(2)        // now [1, 2]
sion[6].dictionary!["two"] = 2  // now ["one":1,"two":2]

When you assign values to SION array with an out-of-bound index, it is automatically streched with unassigned elements set to null, just like an ECMAScript Array

sion[10] = false	// sion[6...9] are null

As you may have guessed by now, a blank SION dictionary is:

sion = SION([:])

And manipulate intuitively like so.

sion["nil"]         = nil
sion["bool"]        = false
sion["int"]         = 0
sion["double"]      = 0.0
sion["string"]      = ""
sion["array"]       = []
sion["dictionary"]  = [:]

deep traversal

SION is a recursive data type. For recursive data types, you need a recursive method that traverses the data deep down. For that purpuse, SION offers .pick and .walk.

.pick is a ".deepFilter" that filters recursively. You've already seen it above. It takes a filter function of type (SION)->Bool. That function is applied to all leaf values of the tree and leaves that do not meet the predicate are pruned.

// because property list does not accept null
let sion4plist = sion.pick{ !$0.isNil }

.walk is a deepMap that transforms recursively. This one is a little harder because you have to consider what to do on node and leaves separately. To make your life easier three different versions of .walk are provided. The first one just takes a leaf node.

// square all ints and leave anything else 
SION([0,[1,[2,3,[4,5,6]]], true]).walk {
    guard let n = $0.int else { return $0 }
    return SION(n * n)
}

The second forms just takes a node. Instead of explaining it, let me show you how .pick is implemented by extending SION with .select that does exactly the same as .pick.

extension SION {
    func select(picker:(SION)->Bool)->SION {
        return self.walk{ node, pairs, depth in
            switch node.type {
            case .array:
                return .Array(pairs.map{ $0.1 }.filter({ picker($0) }) )
            case .dictionary:
                var o = [Key:Value]()
                pairs.filter{ picker($0.1) }.forEach{ o[$0.0.key!] = $0.1 }
                return .Dictionary(o)
            default:
                return .Error(.notIterable(node.type))
            }
        }
    }
}

And the last form takes both. Unlike the previous ones this one can return other than SION . Here is how .yaml is implemented.

extension SION {
    public var yaml:String {
        return self.walk(depth:0, collect:{ node, pairs, depth in
            let indent = Swift.String(repeating:"  ", count:depth)
            var result = ""
            switch node.type {
            case .array:
                guard !pairs.isEmpty else { return "[]"}
                result = pairs.map{ "- " + $0.1}.map{indent + $0}.joined(separator: "\n")
            case .dictionary:
                guard !pairs.isEmpty else { return "{}"}
                result = pairs.sorted{ $0.0.description < $1.0.description }.map{
                    let k = $0.0.string ?? $0.0.description
                    let q = k.rangeOfCharacter(from: .newlines) != nil
                    return (q ? k.debugDescription : k) + ": "  + $0.1
                }.map{indent + $0}.joined(separator: "\n")
            default:
                break   // never reaches here
            }
            return "\n" + result
        },visit:{
            if $0.isNil { return  "~" }
            if let s = $0.string {
                return s.rangeOfCharacter(from: .newlines) == nil ? s : s.debugDescription
            }
            return $0.description
        })
    }
}

Protocol Conformance

  • SION is Equatable so you can check if two JSONs are the same.
SION(string:foo) == SION(jsonUrlString:"https://example.com/whereever")

  • SION is Hashable so you can use it as a dictionary key.

  • SION is ExpressibleBy*Literal. That's why you can initialize w/ variable:JSON construct show above.

  • SION is CustomStringConvertible whose .description is always a valid SION.

  • SION is Codable.

  • SION is Sequence. But when you iterate, be careful with the key.

let sa:SION = [nil, true, 1, "one", [1], ["one":1]]
// wrong!
for v in ja {
	//
}
// right!
for (i, v) in sa {
	// i is NOT an Integer but SION
	// To access its value, say i.int!
}
let sd:SION = [
    "null":nil, "bool":false, "number":0, "string":"",
    "array":[], "object":[:]
]
for (k, v) in sd {
	// k is NOT an Integer but SION.
	// To access its value, say k.string!
}

That is because swift demands to return same Element type. If you feel this counterintuitive, you can simply use .array or .dictionary:

for v in sa.array! {
	// ...
}
for (k, v) in dictionary! {
	// ...
}

Error handling

Once inited, SION never fails. That is, it never becomes nil. Instead of being failable or throwing exceptions, SION has a special value .Error(.ErrorType) which propagates across the method invocations. The following code examines the error should it happen.

if let e = sion.error {
	debugPrint(e.type)
	if let nsError = e.nsError {
		// do anything with nsError
	}
}