Do you need to handle the root cause of failure in decoding JSON?
We often process the value as a default value if it could not be decoded from JSON. (Recovering with a default value)
However, doing that might cause a serious problem and hide the actual root cause in the app.
Recovering with a default value is not a bad choice, it's important to know the JSON represents unexpected shape or value before recovering.
let json: JSON
do {
self.id = try json.next("id").getString()
} catch {
print(error)
// We can know why decoding failed from error.
// Not found "id" or "id" found but it was not `string` or something else.
// that's why here recover the value to fill `self.id`
self.id = "unknown"
}
JAYSON provides 2 ways of accessing to JSON object.
- Easy access (with dynamic-member-lookup)
let urlString: String? = json[3]?.shot?.images?.hidpi_image?.string
- Strict access (with dynamic-member-lookup)
We can know where error was caused. (with JSONError)
let id: String = try json
.next(0)
.next("id")
.getString()
JAYSON
Strict and Scalable JSON library. And also supports dynamicMemberLookup
Requirements
Swift 5+ iOS
Usage
Read JSON
Easy Access
let urlString: String? = json[3]?["shot"]?["images"]?["hidpi_image"]?.string
Using dynamicMemberLookup
let urlString: String? = json[3]?.shot?.images?.hidpi_image?.string
Strict Access (try-catch)
if the value does not exist, throw JSONError
Failed location can be known from JSONError
Get Value (String, Bool, Number)
let id: String = try json
.next(0)
.next("id")
.getString()
Using dynamicMemberLookup
let id: String = try json
.next(0)
.next(\.id)
.getString()
Get Value with Decoder (Custom Object)
Using the Decoder can be transformed in a custom object. And, throwable
let imageURL: URL = try json
.next(0)
.next("image")
.next("hidpi_image")
.get {
URL.init(string: try $0.getString())!
}
General Getter
Strict getters
extension JSON {
public func getDictionary() throws -> [String : JSON]
public func getArray() throws -> [JSON]
public func getNumber() throws -> NSNumber
public func getInt() throws -> Int
public func getInt8() throws -> Int8
public func getInt16() throws -> Int16
public func getInt32() throws -> Int32
public func getInt64() throws -> Int64
public func getUInt() throws -> UInt
public func getUInt8() throws -> UInt8
public func getUInt16() throws -> UInt16
public func getUInt32() throws -> UInt32
public func getUInt64() throws -> UInt64
public func getString() throws -> String
public func getBool() throws -> Bool
public func getFloat() throws -> Float
public func getDouble() throws -> Double
}
///
extension JSON {
public func get<T>(_ s: (JSON) throws -> T) rethrows -> T
}
Optional Read-only properties
extension JSON {
public var dictionary: [String : Any]? { get }
public var array: [Any]? { get }
public var string: String? { get }
public var number: NSNumber? { get }
public var double: Double? { get }
public var float: Float? { get }
public var int: Int? { get }
public var uInt: UInt? { get }
public var int8: Int8? { get }
public var uInt8: UInt8? { get }
public var int16: Int16? { get }
public var uInt16: UInt16? { get }
public var int32: Int32? { get }
public var uInt32: UInt32? { get }
public var int64: Int64? { get }
public var uInt64: UInt64? { get }
public var bool: Bool? { get }
}
Initialize JSON
let jsonData: Data = ...
let json = try JSON(data: jsonData)
let jsonData: Data
let json: Any = try JSONSerialization.jsonObject(with: data, options: [])
let json = try JSON(any: json)
let userInfo: [AnyHashable: Any]
let json = try JSON(any: json)
let objects: [Any]
let json = try JSON(any: json)
In the case of the following try it is not required.
let object: [String : JSON]
let json = JSON(object)
let object: [JSON]
let json = JSON(object)
let object: [JSONWritableType]
let json = JSON(object)
let object: [String : JSONWritableType]
let json = JSON(object)
Get current path (Debugging information.)
let path = try json
.next(0)
.next("image")
.next("hidpi_image")
.currentPath()
// path => "[0]["image"]["hidpi_image"]"
JSONError
If you have access that does not exist key, throw JSONError.
public enum JSONError: Error {
case notFoundKey(key: String, json: JSON)
case notFoundIndex(index: Int, json: JSON)
case failedToGetString(source: Any, json: JSON)
case failedToGetBool(source: Any, json: JSON)
case failedToGetNumber(source: Any, json: JSON)
case failedToGetArray(source: Any, json: JSON)
case failedToGetDictionary(source: Any, json: JSON)
case decodeError(source: Any, json: JSON, decodeError: Error)
case invalidJSONObject
}
example:
do {
let urlString: String = try json
.next("shots")
.next(0)
.next("user")
.next("profile_image")
.next("foo") // ‼️ throw
.getString()
} catch {
print(error)
}
Output jsonError
notFoundKey("foo",
json
Path: Root->["shots"][0]["user"]["profile_image"]
SourceType: dictionary
Source:
{
large = "https://...";
medium = "https://...";
small = "https://...";
})
Go Back JSON hierarchy
try json
.next(0)
.next("image")
.back() // <---
.next("image")
.next("hidpi_image")
Import Example (dribbble API)
let json = try! JSON(data)
struct Shot {
let id: Int
let title: String
let width: Int
let height: Int
let hidpiImageURLString: String?
let normalImageURLString: String
let teaserImageURLString: String
}
do {
let shots: [Shot] = try json.getArray().map { json -> Shot in
let imagesjson = try json.next("images")
return Shot(
id: try json.next("id").getInt(),
title: try json.next("title").getString(),
width: try json.next("width").getInt(),
height: try json.next("height").getInt(),
hidpiImageURLString: try? imagesjson.next("hidpi").getString(),
normalImageURLString: try imagesjson.next("normal").getString(),
teaserImageURLString: try imagesjson.next("teaser").getString()
)
}
print(shots)
} catch {
print(error)
}
Write JSON
var json = JSON()
json["id"] = 18737649
json["active"] = true
json["name"] = "muukii"
var images = [String:JSON]()
images["large"] = "http://...foo"
images["medium"] = "http://...bar"
images["small"] = "http://...fuzz"
json["images"] = JSON(images)
let data = try json.data(options: .prettyPrinted)
-> data
{
"name" : "muukii",
"active" : true,
"id" : 18737649,
"images" : {
"large" : "http:\/\/...foo",
"small" : "http:\/\/...fuzz",
"medium" : "http:\/\/...bar"
}
}
json Convertible Examples
var json = JSON()
json["String"] = "String"
json["NSString"] = JSON("NSString" as NSString)
json["NSNumber"] = NSNumber(value: 0)
json["Int"] = 64
json["Int8"] = JSON(8 as Int8)
json["Int16"] = JSON(16 as Int16)
json["Int32"] = JSON(32 as Int32)
json["Int64"] = JSON(64 as Int64)
json["UInt"] = JSON(64 as UInt)
json["UInt8"] = JSON(8 as UInt8)
json["UInt16"] = JSON(16 as UInt16)
json["UInt32"] = JSON(32 as UInt32)
json["UInt64"] = JSON(64 as UInt64)
json["Bool_true"] = true
json["Bool_false"] = false
json["Float"] = JSON(1.0 / 3.0 as Float)
json["Double"] = JSON(1.0 / 3.0 as Double)
json["CGFloat"] = JSON(1.0 / 3.0 as CGFloat)
Installation
json is available through CocoaPods. To install it, simply add the following line to your Podfile:
pod "JAYSON"
Author
muukii, [email protected]
License
json is available under the MIT license. See the LICENSE file for more info.
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