What do JSONSerialization options do and how do they change jsonResult?
ios, json, swift, swift3
Solution
Short answer for the first two options:
Ignore them in Swift!
In Swift you can make objects mutable just with the `var` keyword.
In Objective-C on the other hand you need
- `NSJSONReadingMutableContainers` to make the nested collection types mutable `NSArray` → `NSMutableArray` and `NSDictionary` → `NSMutableDictionary`.
- `NSJSONReadingMutableLeaves` to make the value strings mutable → `NSMutableString`.
In both Objective-C and Swift if you are only reading the JSON you don't need mutability at all.
The third option `NSJSONReadingAllowFragments` is important if the root object of the received JSON is not an array and not a dictionary. If it is an array or dictionary you can omit that option, too.
The pair of empty brackets `[]` represents `No options` (the `options` parameter can be omitted in Swift 3+).
Problem
I am using `JSONSerialization` quite often in my project. Here is an example of my `JSONSerialization` code: ``` let json = try JSONSerialization.jsonObject(with: data!, options: []) as? [String: Any] ``` Note: Options are missing for purpose and I normally have them in my project. My problem is that I am not pretty sure what do these `options: []` do? What I have found about options: NSJSONReadingMutableContainers: Specifies that arrays and dictionaries are created as mutable objects. NSJSONReadingMutableLeaves: Specifies that leaf strings in the JSON object graph are created as instances of NSMutableString. NSJSONReadingAllowFragments: Specifies that the parser should allow top-level objects that are not an instance of NSArray or NSDictionary. Note2: I found those definitions on : https://developer.apple.com/reference/foundation/nsjsonreadingoptions My question is: Can someone please explain me differences between those options , what should I use them for and if you could show me some code example of those options it would be perfect :). Any help appreciated. Thanks.