将嵌套词典保存在UserDefaults中并管理重复检查[Swift 4.2]

Question

I have a nested Dictionary required to save in UserDefaults and share to extension. The dictionary structure like below:

let dict = [
        "Sections" : [
            ["Title" : "Title1", "Items": ["item1-1", "item1-2", "item1-3"]],
            ["Title" : "Title2", "Items": ["item2-1", "item2-2", "item2-3", "item2-4"]],
            ["Title" : "Title3", "Items": ["item3-1"]],
        ]
    ]

Which saved successfully with:

UserDefaults(suiteName: "group.identifier.test")!.setValue(dict, forKey: "savedDict")

But now I wish to get it back and check is Title2 already exists, if yes then delete it and add again with new Items

I used to do following but can't get the Title back:

let savedDict:[String:AnyObject] = UserDefaults(suiteName: "group.identifier.test")!.object(forKey: "savedDict") as! Dictionary

success to get the data under "Sections" by following code

let savedSection = savedDict["Sections"]
print("Saved Section: \(savedSection)")

but not able to get the Title with:

print("Saved Title: \(savedSection!["Title"])") *// return nil*

I tried for (key, value) too, but fired a data type error

for (key, value) in savedSection{  *// Type 'AnyObject?' does not conform to protocol 'Sequence'*
    print("Key: \(key) Value: \(value)")
}

May I know is there any way to get the "Title" back for checking and update? Am I using the wrong way to store this kind of nested data?

Many Thanks!

Answer 1

in your code

 print("Saved Title: \(savedSection!["Title"])") *// return nil*

here it should be

  if let savedSection = savedDict["Sections"] as?  [[String : Any]] { //EDIT***

      print("Saved Title: \(savedSection[0]["Title"])") *// inplace of 0 any index you want, 
  }

as if now in your dictionary there are three elements in section so it safe to get value at 0, hope you understood that the underlying dictionary is array of dictionary in sections key, also instead of using dictionary you can use struct or class to save your data and while getting it retrieve it as that struct type.

Answer 2

First of all, never use KVC method setValue(:forKey with UserDefaults .

There is generic set(:forKey . And there is dictionary(forKey: to get a [String:Any] dictionary back

The value for key Sections is an array (index-based). Lets assume you have this new data

let newTitle2 : [String:Any] = ["Title" : "Title2", "Items": ["item4-1", "item4-2", "item4-3"]]

This is a way to load the dictionary – you should always safely check if the dictionary exists – update it and save it back. If the item for "Title2" exists it will be overwritten otherwise the new item is appended to the array.

let groupDefaults = UserDefaults(suiteName: "group.identifier.test")!
if var savedDict = groupDefaults.dictionary(forKey: "savedDict"), 
   var sections = savedDict["Sections"] as? [[String:Any]] {
      if let title2Index = sections.firstIndex(where: {($0["Title"] as! String) == "Title2"}) {
         sections[title2Index] = newTitle2
      } else {
         sections.append(newTitle2)
      }
      savedDict["Sections"] = sections
      groupDefaults.set(savedDict, forKey: "savedDict")
}