AEMDictionary.swift

protocol AEMValue { }
extension String: AEMValue { }
extension Int: AEMValue { }

struct AEMDictionary<T> {
    
    private let container: [String: T]
    
    init(_ dict: [String: T]) {
          container = dict
      }
    
    private static func aemDefaultValue(_ type: T.Type) -> T {
        var defaultValue: AEMValue
        switch type {
        case is String.Type:
            defaultValue = "Content Unavailable"
        case is Int.Type:
            defaultValue = 0
        default:
            fatalError("Default Value is Missing for \(T.self)")
        }
        guard let value = defaultValue as? T else {
            fatalError("\(T.self) should conform to AEMValue protocol.")
        }
        return value
    }
    
  
    public func fetch(_ key: String, defaultValue: (T.Type) -> T = aemDefaultValue) -> T {
        return container[key] ?? defaultValue(T.self)
    }

}


// Initialize AEM dictionary
var dict = AEMDictionary(["name": "boudhayan"])

// Cast to any supported type
var jj: String = dict.fetch("lastName")

// fetch default value
print(dict.fetch("lastName"))

// expect a different default value other than which was set initially
print(dict.fetch("lastName", defaultValue: { _ in "biswas" }))