从'String ?!'垮掉 'String'只展开选项; 你的意思是用'!!'吗？在迅速

Question

源代码如下

let json = try NSJSONSerialization.JSONObjectWithData(data!, options: .AllowFragments)
                        if let blogs = json["profile_image_url"] as? String {

                            userImage = blogs//json["profile_image_url"] as! String
                            print("USER IMAGE:\(userImage)")

我是如何解决这个问题的

Answer 1

您希望Optional在使用之前测试和解包任何内容.这包括演员表as?.如果可以避免它,则不应使用强制解包或显式解包Optional(标记为a !),因为它们会导致意外的运行时崩溃.

import Foundation

// create test data
let testJson = ["profile_image_url": "http://some.site.com/"]
var data: NSData?

// convert to NSData as JSON
do {
  data = try NSJSONSerialization.dataWithJSONObject(testJson, options: [])
} catch let error as NSError {
  print(error)
}

// decode NSData
do {
  // test and unwrap data
  if let data = data {
    let json = try NSJSONSerialization.JSONObjectWithData(data, options: .AllowFragments)
    // test and unwrap cast to String
    if let userImage = json["profile_image_url"] as? String {
      print("USER IMAGE:\(userImage)")
    }
  }
} catch let error as NSError {
  print(error)
}