Swift 4 Tuple Iteration - swift

Question

I am trying to retrieve wallpapers from Bing by json in Swift 4
https://www.bing.com/HPImageArchive.aspx?format=js&idx=0&n=8&mkt=en-US
But images property is a tuple with another objects. I can not iterate this tuple and reach the url values so that I can collect them in an array.
(
{
bot = 1;
copyright = "For the winter solstice, Santa Fe's Farolito Walk (\U00a9 Julien McRoberts/Danita Delimont)";
copyrightlink = "http://www.bing.com/search?q=santa+fe+new+mexico&form=hpcapt&filters=HpDate:%2220181221_0800%22";
drk = 1;
enddate = 20181222;
fullstartdate = 201812210800;
hs = (
);
hsh = 6ba85f1fbab1b9a290a19af763ca404d;
quiz = "/search?q=Bing+homepage+quiz&filters=WQOskey:%22HPQuiz_20181221_AdobeSantaFe%22&FORM=HPQUIZ";
startdate = 20181221;
title = "All is bright in Santa Fe";
top = 1;
url = "/az/hprichbg/rb/AdobeSantaFe_EN-US4037753534_1920x1080.jpg";
urlbase = "/az/hprichbg/rb/AdobeSantaFe_EN-US4037753534";
wp = 1;
},
{
bot = 1;
copyright = "Nabana-no-Sato gardens at Nagashima Spa Land in Kuwana, Japan (\U00a9 Julian Krakowiak/Alamy)";
copyrightlink = "http://www.bing.com/search?q=nabana+no+sato+nagashima+spa+land&form=hpcapt&filters=HpDate:%2220181220_0800%22";
drk = 1;
enddate = 20181221;
fullstartdate = 201812200800;
hs = (
);
hsh = eda366ca6eee5c653a59d8f16a54ae63;
quiz = "/search?q=Bing+homepage+quiz&filters=WQOskey:%22HPQuiz_20181220_WinterIllumination%22&FORM=HPQUIZ";
startdate = 20181220;
title = "Winter illuminations in Nabana-no-Sato";
top = 1;
url = "/az/hprichbg/rb/WinterIllumination_EN-US0071328313_1920x1080.jpg";
urlbase = "/az/hprichbg/rb/WinterIllumination_EN-US0071328313";
wp = 0;
},
{
bot = 1;
copyright = "The Charles Bridge in Prague, Czech Republic (\U00a9 borchee/E+/Getty Images)";
copyrightlink = "http://www.bing.com/search?q=prague&form=hpcapt&filters=HpDate:%2220181219_0800%22";
drk = 1;
enddate = 20181220;
fullstartdate = 201812190800;
hs = (
);
hsh = 37c19c3f45952fd81c429e5e92c386e9;
quiz = "/search?q=Bing+homepage+quiz&filters=WQOskey:%22HPQuiz_20181219_PragueChristmas%22&FORM=HPQUIZ";
startdate = 20181219;
title = "Snow falls on Bohemia";
top = 1;
url = "/az/hprichbg/rb/PragueChristmas_EN-US8649790921_1920x1080.jpg";
urlbase = "/az/hprichbg/rb/PragueChristmas_EN-US8649790921";
wp = 1;
},
{
bot = 1;
copyright = "For the anniversary of the premiere of 'The Nutcracker,' a scene of the Moscow Ballet performing the popular dance (\U00a9 Tytus Zmijewski/Epa/Shutterstock)";
copyrightlink = "http://www.bing.com/search?q=the+nutcracker&form=hpcapt&filters=HpDate:%2220181218_0800%22";
drk = 1;
enddate = 20181219;
fullstartdate = 201812180800;
hs = (
);
hsh = b6303e82458de5692e94b26cb332fbd1;
quiz = "/search?q=Bing+homepage+quiz&filters=WQOskey:%22HPQuiz_20181218_NutcrackerSeason%22&FORM=HPQUIZ";
startdate = 20181218;
title = "A holiday tradition is born";
top = 1;
url = "/az/hprichbg/rb/NutcrackerSeason_EN-US8373379424_1920x1080.jpg";
urlbase = "/az/hprichbg/rb/NutcrackerSeason_EN-US8373379424";
wp = 0;
},
{
bot = 1;
copyright = "Wilbur Wright gliding down Big Kill Devil Hill in Kitty Hawk, North Carolina (\U00a9 Library of Congress)";
copyrightlink = "http://www.bing.com/search?q=wright+brothers+first+flight&form=hpcapt&filters=HpDate:%2220181217_0800%22";
drk = 1;
enddate = 20181218;
fullstartdate = 201812170800;
hs = (
);
hsh = 5a132d06c5e7b66f0a1ec9f434a0dca1;
quiz = "/search?q=Bing+homepage+quiz&filters=WQOskey:%22HPQuiz_20181217_WrightGlider%22&FORM=HPQUIZ";
startdate = 20181217;
title = "Wright brothers fly into history";
top = 1;
url = "/az/hprichbg/rb/WrightGlider_EN-US10185286591_1920x1080.jpg";
urlbase = "/az/hprichbg/rb/WrightGlider_EN-US10185286591";
wp = 0;
},
{
bot = 1;
copyright = "Holiday decorations on a canal in Murano, Italy (\U00a9 John Warburton-Lee/DanitaDelimont.com)";
copyrightlink = "http://www.bing.com/search?q=murano+island&form=hpcapt&filters=HpDate:%2220181216_0800%22";
drk = 1;
enddate = 20181217;
fullstartdate = 201812160800;
hs = (
);
hsh = c4cc26f7a803502632d940f9466e2b7c;
quiz = "/search?q=Bing+homepage+quiz&filters=WQOskey:%22HPQuiz_20181216_MuranoChristmas%22&FORM=HPQUIZ";
startdate = 20181216;
title = "Murano aglow";
top = 1;
url = "/az/hprichbg/rb/MuranoChristmas_EN-US10759540271_1920x1080.jpg";
urlbase = "/az/hprichbg/rb/MuranoChristmas_EN-US10759540271";
wp = 1;
},
{
bot = 1;
copyright = "The Stoneman Bridge on the Merced River in Yosemite National Park (\U00a9 Ron_Thomas/E+/Getty Images)";
copyrightlink = "http://www.bing.com/search?q=yosemite+national+park&form=hpcapt&filters=HpDate:%2220181215_0800%22";
drk = 1;
enddate = 20181216;
fullstartdate = 201812150800;
hs = (
);
hsh = 6a49f8fc62b09ce83305ac0a13000a7a;
quiz = "/search?q=Bing+homepage+quiz&filters=WQOskey:%22HPQuiz_20181215_YosemiteBridge%22&FORM=HPQUIZ";
startdate = 20181215;
title = "Season of solitude in Yosemite";
top = 1;
url = "/az/hprichbg/rb/YosemiteBridge_EN-US10544416282_1920x1080.jpg";
urlbase = "/az/hprichbg/rb/YosemiteBridge_EN-US10544416282";
wp = 1;
},
{
bot = 1;
copyright = "A female northern cardinal (\U00a9 Matthew Studebaker/Minden Pictures)";
copyrightlink = "http://www.bing.com/search?q=northern+cardinal&form=hpcapt&filters=HpDate:%2220181214_0800%22";
drk = 1;
enddate = 20181215;
fullstartdate = 201812140800;
hs = (
);
hsh = 0dcf20ffcfd5413167161ad20b412fb5;
quiz = "/search?q=Bing+homepage+quiz&filters=WQOskey:%22HPQuiz_20181214_CardinalBerries%22&FORM=HPQUIZ";
startdate = 20181214;
title = "The Christmas Bird Count begins";
top = 1;
url = "/az/hprichbg/rb/CardinalBerries_EN-US11262203078_1920x1080.jpg";
urlbase = "/az/hprichbg/rb/CardinalBerries_EN-US11262203078";
wp = 1;
}
)
How can I handle this JSON tuple in Swift 4?

Answer 1

That's not a tuple.
That's how a NSArray is printed (that's the description implementation result). It's more Objective-C like.
(
content...
)
With force unwrap (use of !) that I'd strongly recommend to not use in production, and use if let/guard let instead (because it will cause a crash if it fails the unwrap). I used force unwrap to be more direct, that's all, show the logic.
let dataJSON = initialJSONData
//Your JSON is a Dictionary at top level
let json = try! JSONSerialization.jsonObject(with: dataJSON, options: []) as! [String: Any]
//The value of a images key is an Array of Dictionaries
let imagesArray = json["images"] as! [[String: Any]]
let imagesURLStr = imagesArray.flatMap{ $0["url"] as? String }
Now, if you use Swift 4+, I'd recommend to use Codable:
struct Result: Codable {
let images: [Image]
struct Image: Codable {
let url: String
}
}
To call it:
let jsonDecoder = JSONDecoder()
let result = try! jsonDecoder.decode(Result.self, from: dataJSON)
let images = result.images
let imagesURLStr = images.map{ $0.url }
Side Note:
This code is not tested, written only here, so there might be a typo error, a minor compiler issue but it shouldn't be un-fixable.

Answer 2

With the help of quicktype.io, let's use these structs :
struct Result: Codable {
let images: [Image]
let tooltips: Tooltips
}
struct Image: Codable {
let startdate, fullstartdate, enddate, url: String
let urlbase, copyright: String
let copyrightlink: String
let title, quiz: String
let wp: Bool
let hsh: String
let drk, top, bot: Int
let hs: [JSONAny]
}
struct Tooltips: Codable {
let loading, previous, next, walle: String
let walls: String
}
// MARK: Encode/decode helpers
class JSONNull: Codable, Hashable {
public static func == (lhs: JSONNull, rhs: JSONNull) -> Bool {
return true
}
public var hashValue: Int {
return 0
}
public init() {}
public required init(from decoder: Decoder) throws {
let container = try decoder.singleValueContainer()
if !container.decodeNil() {
throw DecodingError.typeMismatch(JSONNull.self, DecodingError.Context(codingPath: decoder.codingPath, debugDescription: "Wrong type for JSONNull"))
}
}
public func encode(to encoder: Encoder) throws {
var container = encoder.singleValueContainer()
try container.encodeNil()
}
}
class JSONCodingKey: CodingKey {
let key: String
required init?(intValue: Int) {
return nil
}
required init?(stringValue: String) {
key = stringValue
}
var intValue: Int? {
return nil
}
var stringValue: String {
return key
}
}
class JSONAny: Codable {
let value: Any
static func decodingError(forCodingPath codingPath: [CodingKey]) -> DecodingError {
let context = DecodingError.Context(codingPath: codingPath, debugDescription: "Cannot decode JSONAny")
return DecodingError.typeMismatch(JSONAny.self, context)
}
static func encodingError(forValue value: Any, codingPath: [CodingKey]) -> EncodingError {
let context = EncodingError.Context(codingPath: codingPath, debugDescription: "Cannot encode JSONAny")
return EncodingError.invalidValue(value, context)
}
static func decode(from container: SingleValueDecodingContainer) throws -> Any {
if let value = try? container.decode(Bool.self) {
return value
}
if let value = try? container.decode(Int64.self) {
return value
}
if let value = try? container.decode(Double.self) {
return value
}
if let value = try? container.decode(String.self) {
return value
}
if container.decodeNil() {
return JSONNull()
}
throw decodingError(forCodingPath: container.codingPath)
}
static func decode(from container: inout UnkeyedDecodingContainer) throws -> Any {
if let value = try? container.decode(Bool.self) {
return value
}
if let value = try? container.decode(Int64.self) {
return value
}
if let value = try? container.decode(Double.self) {
return value
}
if let value = try? container.decode(String.self) {
return value
}
if let value = try? container.decodeNil() {
if value {
return JSONNull()
}
}
if var container = try? container.nestedUnkeyedContainer() {
return try decodeArray(from: &container)
}
if var container = try? container.nestedContainer(keyedBy: JSONCodingKey.self) {
return try decodeDictionary(from: &container)
}
throw decodingError(forCodingPath: container.codingPath)
}
static func decode(from container: inout KeyedDecodingContainer<JSONCodingKey>, forKey key: JSONCodingKey) throws -> Any {
if let value = try? container.decode(Bool.self, forKey: key) {
return value
}
if let value = try? container.decode(Int64.self, forKey: key) {
return value
}
if let value = try? container.decode(Double.self, forKey: key) {
return value
}
if let value = try? container.decode(String.self, forKey: key) {
return value
}
if let value = try? container.decodeNil(forKey: key) {
if value {
return JSONNull()
}
}
if var container = try? container.nestedUnkeyedContainer(forKey: key) {
return try decodeArray(from: &container)
}
if var container = try? container.nestedContainer(keyedBy: JSONCodingKey.self, forKey: key) {
return try decodeDictionary(from: &container)
}
throw decodingError(forCodingPath: container.codingPath)
}
static func decodeArray(from container: inout UnkeyedDecodingContainer) throws -> [Any] {
var arr: [Any] = []
while !container.isAtEnd {
let value = try decode(from: &container)
arr.append(value)
}
return arr
}
static func decodeDictionary(from container: inout KeyedDecodingContainer<JSONCodingKey>) throws -> [String: Any] {
var dict = [String: Any]()
for key in container.allKeys {
let value = try decode(from: &container, forKey: key)
dict[key.stringValue] = value
}
return dict
}
static func encode(to container: inout UnkeyedEncodingContainer, array: [Any]) throws {
for value in array {
if let value = value as? Bool {
try container.encode(value)
} else if let value = value as? Int64 {
try container.encode(value)
} else if let value = value as? Double {
try container.encode(value)
} else if let value = value as? String {
try container.encode(value)
} else if value is JSONNull {
try container.encodeNil()
} else if let value = value as? [Any] {
var container = container.nestedUnkeyedContainer()
try encode(to: &container, array: value)
} else if let value = value as? [String: Any] {
var container = container.nestedContainer(keyedBy: JSONCodingKey.self)
try encode(to: &container, dictionary: value)
} else {
throw encodingError(forValue: value, codingPath: container.codingPath)
}
}
}
static func encode(to container: inout KeyedEncodingContainer<JSONCodingKey>, dictionary: [String: Any]) throws {
for (key, value) in dictionary {
let key = JSONCodingKey(stringValue: key)!
if let value = value as? Bool {
try container.encode(value, forKey: key)
} else if let value = value as? Int64 {
try container.encode(value, forKey: key)
} else if let value = value as? Double {
try container.encode(value, forKey: key)
} else if let value = value as? String {
try container.encode(value, forKey: key)
} else if value is JSONNull {
try container.encodeNil(forKey: key)
} else if let value = value as? [Any] {
var container = container.nestedUnkeyedContainer(forKey: key)
try encode(to: &container, array: value)
} else if let value = value as? [String: Any] {
var container = container.nestedContainer(keyedBy: JSONCodingKey.self, forKey: key)
try encode(to: &container, dictionary: value)
} else {
throw encodingError(forValue: value, codingPath: container.codingPath)
}
}
}
static func encode(to container: inout SingleValueEncodingContainer, value: Any) throws {
if let value = value as? Bool {
try container.encode(value)
} else if let value = value as? Int64 {
try container.encode(value)
} else if let value = value as? Double {
try container.encode(value)
} else if let value = value as? String {
try container.encode(value)
} else if value is JSONNull {
try container.encodeNil()
} else {
throw encodingError(forValue: value, codingPath: container.codingPath)
}
}
public required init(from decoder: Decoder) throws {
if var arrayContainer = try? decoder.unkeyedContainer() {
self.value = try JSONAny.decodeArray(from: &arrayContainer)
} else if var container = try? decoder.container(keyedBy: JSONCodingKey.self) {
self.value = try JSONAny.decodeDictionary(from: &container)
} else {
let container = try decoder.singleValueContainer()
self.value = try JSONAny.decode(from: container)
}
}
public func encode(to encoder: Encoder) throws {
if let arr = self.value as? [Any] {
var container = encoder.unkeyedContainer()
try JSONAny.encode(to: &container, array: arr)
} else if let dict = self.value as? [String: Any] {
var container = encoder.container(keyedBy: JSONCodingKey.self)
try JSONAny.encode(to: &container, dictionary: dict)
} else {
var container = encoder.singleValueContainer()
try JSONAny.encode(to: &container, value: self.value)
}
}
}
We can get the url properties this way:
//Create the URL
guard let url = URL(string: "https://www.bing.com/HPImageArchive.aspx?format=js&idx=0&n=8&mkt=en-US") else {
fatalError("Invalid URL")
}
//Fetch the data from the URL
URLSession.shared.dataTask(with: url, completionHandler: {(data, response, error) -> Void in
guard let jsonData = data, error == nil else {
fatalError("Data error")
}
let jsonDecoder = JSONDecoder()
do {
let result = try jsonDecoder.decode(Result.self, from: jsonData)
let images = result.images
let urls = images.map { $0.url }
urls.forEach { print($0) }
}
catch {
print(error)
}
}).resume()
This prints:
/az/hprichbg/rb/AdobeSantaFe_EN-US4037753534_1920x1080.jpg
/az/hprichbg/rb/WinterIllumination_EN-US0071328313_1920x1080.jpg
/az/hprichbg/rb/PragueChristmas_EN-US8649790921_1920x1080.jpg
/az/hprichbg/rb/NutcrackerSeason_EN-US8373379424_1920x1080.jpg
/az/hprichbg/rb/WrightGlider_EN-US10185286591_1920x1080.jpg
/az/hprichbg/rb/MuranoChristmas_EN-US10759540271_1920x1080.jpg
/az/hprichbg/rb/YosemiteBridge_EN-US10544416282_1920x1080.jpg
/az/hprichbg/rb/CardinalBerries_EN-US11262203078_1920x1080.jpg