如何在Swift中安全解开字典中深层嵌套的值？

Question

I understand how to print the values of upper level things such as the value of "email" or the value of "name" but how would I safely unwrap the dictionary to print a deeper nested value such as the value of "url"?

Answer 1

Nesting just means that the value for a particular key in your top level [String: Any] dictionary is another [String: Any] - so you just need to cast it to access nested objects.

// assuming you have an object `json` of `[String: Any]`
if let pictureJSON = json["picture"] as? [String: Any] {
    // if the JSON is correct, this will have a string value. If not, this will be nil
    let nestedURL = pictureJSON["url"] as? String
}

I feel I should mention that the process of serializing/de-serializing JSON in Swift took a big leap with Codable in Swift 4. If you have a model object you want to map this JSON to, this whole thing can be automated away (including nested objects - you just supply a nested Swift struct/class conforming to Codable). Here's some Apple documentation on it .

Answer 2

Like that:

if let picture = dictionary["picture"] as? [String:AnyObject] {

        if let url = picture["url"] as? String {

        }

        if let width = picture["width"] as? Int {

        }

    }