基础类

Date相关

包括：DateFormatterTransform, DateTransform, ISO8601DateTransform,CustomDateFormatTransform，TransformType

//这是最基础的协议//后面是协议的扩展和实现 
public protocol TransformType {
    //使用associatedtype关键字进行类型关联
    associatedtype Object
    associatedtype JSON

    func transformFromJSON(_ value: Any?) -> Object?
    func transformToJSON(_ value: Object?) -> JSON?
}

DateTransform

open class DateTransform: TransformType {
    //遵守TransformType协议，实现协议时才指定类型
    public typealias Object = Date
    public typealias JSON = Double

    public init() {}
    //字符串和doule转化为date，否则nil
    open func transformFromJSON(_ value: Any?) -> Date? {
        if let timeInt = value as? Double {
            return Date(timeIntervalSince1970: TimeInterval(timeInt))
        }
        
        if let timeStr = value as? String {
            return Date(timeIntervalSince1970: TimeInterval(atof(timeStr)))
        }
        
        return nil
    }
    //转化为double
    open func transformToJSON(_ value: Date?) -> Double? {
        if let date = value {
            return Double(date.timeIntervalSince1970)
        }
        return nil
    }
}

DateFormatterTransform

//遵守TransformType协议。不过这里的JSON是字符串类型
open class DateFormatterTransform: TransformType {
    public typealias Object = Date
    public typealias JSON = String
    
    public let dateFormatter: DateFormatter
    
    public init(dateFormatter: DateFormatter) {
        self.dateFormatter = dateFormatter
    }
    //String和date的相互转换
    open func transformFromJSON(_ value: Any?) -> Date? {
        if let dateString = value as? String {
            return dateFormatter.date(from: dateString)
        }
        return nil
    }
    
    open func transformToJSON(_ value: Date?) -> String? {
        if let date = value {
            return dateFormatter.string(from: date)
        }
        return nil
    }
}

ISO8601DateTransform(继承DateFormatterTransform)

//国际标准化组织的国际标准ISO 8601是日期和时间的表示方法
open class ISO8601DateTransform: DateFormatterTransform {
    //继承的DateFormatterTransform，复写init方法
    //String和date的相互转换
    public init() {
        let formatter = DateFormatter()
        formatter.locale = Locale(identifier: "en_US_POSIX")
        formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ssZZZZZ"
        
        super.init(dateFormatter: formatter)
    }
    
}

CustomDateFormatTransform(继承DateFormatterTransform)

open class CustomDateFormatTransform: DateFormatterTransform {
    //自定义时间格式
    public init(formatString: String) {
        let formatter = DateFormatter()
        formatter.locale = Locale(identifier: "en_US_POSIX")
        formatter.dateFormat = formatString
        
        super.init(dateFormatter: formatter)
    }
}

TransformOf

open class TransformOf<ObjectType, JSONType>: TransformType {
    public typealias Object = ObjectType
    public typealias JSON = JSONType

    private let fromJSON: (JSONType?) -> ObjectType?
    private let toJSON: (ObjectType?) -> JSONType?
    //初始化定义Object和JSON类型
    public init(fromJSON: @escaping(JSONType?) -> ObjectType?, toJSON: @escaping(ObjectType?) -> JSONType?) {
        self.fromJSON = fromJSON
        self.toJSON = toJSON
    }
  //由block实现具体转换
    open func transformFromJSON(_ value: Any?) -> ObjectType? {
        return fromJSON(value as? JSONType)
    }

    open func transformToJSON(_ value: ObjectType?) -> JSONType? {
        return toJSON(value)
    }
}

URL相关

//字符串和URL的转换
open class URLTransform: TransformType {
    public typealias Object = URL
    public typealias JSON = String
    private let shouldEncodeURLString: Bool
    private let allowedCharacterSet: CharacterSet

    /**
    Initializes the URLTransform with an option to encode URL strings before converting them to an NSURL
    - parameter shouldEncodeUrlString: when true (the default) the string is encoded before passing
    to `NSURL(string:)`
    - returns: an initialized transformer
    */
    /**
    URLFragmentAllowedCharacterSet  "#%<>[\]^`{|}
    
    URLHostAllowedCharacterSet      "#%/<>?@\^`{|}
    
    URLPasswordAllowedCharacterSet  "#%/:<>?@[\]^`{|}
    
    URLPathAllowedCharacterSet      "#%;<>?[\]^`{|}
    
    URLQueryAllowedCharacterSet    "#%<>[\]^`{|}
    
    URLUserAllowedCharacterSet      "#%/:<>?@[\]^`
    */
    public init(shouldEncodeURLString: Bool = true, allowedCharacterSet: CharacterSet = .urlQueryAllowed) {
        self.shouldEncodeURLString = shouldEncodeURLString
        self.allowedCharacterSet = allowedCharacterSet
    }

    open func transformFromJSON(_ value: Any?) -> URL? {
        guard let URLString = value as? String else { return nil }
        
        if !shouldEncodeURLString {
            return URL(string: URLString)
        }
        //特殊字符处理
        guard let escapedURLString = URLString.addingPercentEncoding(withAllowedCharacters: allowedCharacterSet) else {
            return nil
        }
        return URL(string: escapedURLString)
    }

    open func transformToJSON(_ value: URL?) -> String? {
        if let URL = value {
            return URL.absoluteString
        }
        return nil
    }
}

EnumTransform

//枚举与枚举值的相互转换
open class EnumTransform<T: RawRepresentable>: TransformType {
    public typealias Object = T
    public typealias JSON = T.RawValue
    
    public init() {}
    
    open func transformFromJSON(_ value: Any?) -> T? {
        if let raw = value as? T.RawValue {
            return T(rawValue: raw)
        }
        return nil
    }
    
    open func transformToJSON(_ value: T?) -> T.RawValue? {
        if let obj = value {
            return obj.rawValue
        }
        return nil
    }
}

NSDecimalNumberTransform

//精确小数计算与字符串转换
open class NSDecimalNumberTransform: TransformType {
    public typealias Object = NSDecimalNumber
    public typealias JSON = String

    public init() {}

    open func transformFromJSON(_ value: Any?) -> NSDecimalNumber? {
        if let string = value as? String {
            return NSDecimalNumber(string: string)
        } else if let number = value as? NSNumber {
            return NSDecimalNumber(decimal: number.decimalValue)
        } else if let double = value as? Double {
            return NSDecimalNumber(floatLiteral: double)
        }
        return nil
    }

    open func transformToJSON(_ value: NSDecimalNumber?) -> String? {
        guard let value = value else { return nil }
        return value.description
    }
}

DataTransform

open class DataTransform: TransformType {
    public typealias Object = Data
    public typealias JSON = String
    
    public init() {}
    
    open func transformFromJSON(_ value: Any?) -> Data? {
        guard let string = value as? String else{
            return nil
        }
        return Data(base64Encoded: string)
    }
    
    open func transformToJSON(_ value: Data?) -> String? {
        guard let data = value else{
            return nil
        }
        return data.base64EncodedString()
    }
}

DictionaryTransform

///Transforms [String: AnyObject] <-> [Key: Value] where Key is RawRepresentable as String, Value is Mappable
public struct DictionaryTransform<Key, Value>: TransformType where Key: Hashable, Key: RawRepresentable, Key.RawValue == String, Value: Mappable {
    
    public init() {
        
    }
    
    public func transformFromJSON(_ value: Any?) -> [Key: Value]? {
        
        guard let json = value as? [String: Any] else {
            
            return nil
        }
        
        let result = json.reduce([:]) { (result, element) -> [Key: Value] in
            
            guard
            let key = Key(rawValue: element.0),
            let valueJSON = element.1 as? [String: Any],
            let value = Value(JSON: valueJSON)
            else {
                
                return result
            }
            
            var result = result
            result[key] = value
            return result
        }
        
        return result
    }
    
    public func transformToJSON(_ value: [Key: Value]?) -> Any? {
        
        let result = value?.reduce([:]) { (result, element) -> [String: Any] in
            
            let key = element.0.rawValue
            let value = element.1.toJSON()
            
            var result = result
            result[key] = value
            return result
        }
        
        return result
    }
}