CODEWITHSUNDEEP
error-handlingswift2
RyanTCB
RyanTCB

Reputation: 8224

Swift error handling, what are the errors though?

Each guide I find on swift 2.0 error handling shows handling errors on a custom class. I know how to do, try, catch but what I don't know is what to catch. I know I'm testing for certain enum to indicate the error but where or how do i find these error enums if i did not create the class?

Im using 

 class func JSONObjectWithData(_ data: NSData,
                      options opt: NSJSONReadingOptions) throws -> AnyObject

so it says it throws and I would like to handle that but what does it throw? how do I know what enums to catch in the catch block? No doubt I'm missing something obvious but you know what it's like when you just can't spot it?

thanks

Upvotes: 1

Views: 103

Answers (2)

Narendra G
Narendra G

Reputation: 549

And, if you guaranty it should returns object then you could use below code:

let jsonDataObject = try! JSONObjectWithData(someData, options:NSJSONReadingOptions())

Here, advantage is we can avoid to use "do { }" scope of syntax

Upvotes: 0

vadian
vadian

Reputation: 285039

For methods in the Apple frameworks look into the documentation and compare the method signature with its Objective-C equivalent.

In this specific case the Objective-C equivalent is 

+ (id)JSONObjectWithData:(NSData *)data
             options:(NSJSONReadingOptions)opt
               error:(NSError * _Nullable *)error

so the object in the catch statement is an NSError object

do {
  let jsonData = try JSONObjectWithData(someData, options:NSJSONReadingOptions())
} catch let error as NSError {
  print(error)
}

Upvotes: 1

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