Swift/Cocoa json parse error?

Question

New to Swift/iphone dev ...

If I have a string in json that is an array of objs, it can start with a bracket '['. According to the json spec, afaik, this is okay. However, the following blows up as a unit test in swift/xcode:

var json = "[{\"class\":\"ProductDesign\"},{\"class\":\"ProductDesign\"}]"
let jsonObject : AnyObject! = NSJSONSerialization.JSONObjectWithData(json.dataUsingEncoding(NSUTF8StringEncoding), options: NSJSONReadingOptions.MutableContainers, error: nil) as NSDictionary

I've seen blog write-ups of people doing exactly this but it does not work for me (xcode does some funny stuff, popping up :

0x287784:  je     0x28778d                  ; swift_dynamicCastObjCClassUnconditional + 61
0x287786:  addl   $0x10, %esp
0x287789:  popl   %esi
0x28778a:  popl   %edi
0x28778b:  popl   %ebp
0x28778c:  retl   
0x28778d:  leal   0xea35(%esi), %eax
0x287793:  movl   0x468ef(%esi), %ecx
0x287799:  movl   %eax, 0x8(%ecx)
0x28779c:  movl   $0x0, 0xc(%ecx)
0x2877a3:  int3   
0x2877a4:  nopw   %cs:(%eax,%eax)

Any ideas? Bug in this release?? Programmer stupidity?

PLEASE go to json.org and spend the 5-10 minutes it takes to learn JSON. Then you will be a bit more able to actually code what you understand, rather than blindly copying code you don't understand. — Hot Licks
– Hot Licks, Commented Aug 19, 2014 at 1:15
Wow, you sir, have just earned the reputation imo as a jerk. Thanks to those that helped me understand. — Will Hughes
– Will Hughes, Commented Aug 19, 2014 at 3:12

Mike S · Accepted Answer · 2014-08-19 01:05:15Z

3

Your JSON is an Array, but you're casting the result of NSJSONSerialization.JSONObjectWithData to an NSDictionary; cast it to an NSArray instead:

let jsonObject : AnyObject! = NSJSONSerialization.JSONObjectWithData(json.dataUsingEncoding(NSUTF8StringEncoding), options: NSJSONReadingOptions.MutableContainers, error: nil) as NSArray

Note: You can also exclude the AnyObject! type declaration and just do:

let jsonObject = NSJSONSerialization.JSONObjectWithData(json.dataUsingEncoding(NSUTF8StringEncoding), options: NSJSONReadingOptions.MutableContainers, error: nil) as NSArray

answered Aug 19, 2014 at 1:05

Mike S

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2 Comments

Aaron Brager Over a year ago

And to avoid this type of issue in the future, you can use optional casting (as? instead of as)

Will Hughes Over a year ago

Thanks all. Obvious once you told me.

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