Swift Language Reading & Writing JSON Simple JSON parsing into custom objects
Example
Even if third-party libraries are good, a simple way to parse the JSON is provided by protocols
You can imagine you have got an object Todo as
struct Todo {
let comment: String
}
Whenever you receive the JSON, you can handle the plain NSData as shown in the other example using NSJSONSerialization object.
After that, using a simple protocol JSONDecodable
typealias JSONDictionary = [String:AnyObject]
protocol JSONDecodable {
associatedtype Element
static func from(json json: JSONDictionary) -> Element?
}
And making your Todo struct conforming to JSONDecodable does the trick
extension Todo: JSONDecodable {
static func from(json json: JSONDictionary) -> Todo? {
guard let comment = json["comment"] as? String else { return nil }
return Todo(comment: comment)
}
}
You can try it with this json code:
{
"todos": [
{
"comment" : "The todo comment"
}
]
}
When you got it from the API, you can serialize it as the previous examples shown in an AnyObject instance. After that, you can check if the instance is a JSONDictionary instance
guard let jsonDictionary = dictionary as? JSONDictionary else { return }
The other thing to check, specific for this case because you have an array of Todo in the JSON, is the todos dictionary
guard let todosDictionary = jsonDictionary["todos"] as? [JSONDictionary] else { return }
Now that you got the array of dictionaries, you can convert each of them in a Todo object by using flatMap (it will automatically delete the nil values from the array)
let todos: [Todo] = todosDictionary.flatMap { Todo.from(json: $0) }
