Errors in do catch statement in swift - json

Question

I'm trying to explore this new (for me) language, and I'm making an app that like many others retrieve some json data from a server.
in this function (from a tutorial I found) I get 4 errors, and I'm unable to fix it:
func json_parseData(data: NSData) -> NSDictionary? {
do {
let json: AnyObject = try NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainers)
print("[JSON] OK!")
return (json as? NSDictionary)
}catch _ {
print("[ERROR] An error has happened with parsing of json data")
return nil
}
}
the first one is at the "try", xcode suggest me to fix it using "try;"
the others at the "catch" and are this others:
Braced block of statement is an unused closure
Type of expression is ambiguous without more context
Expected while in do-while-loop
please help me to understand

Answer 1

It seems that you are using Xcode 6.x and Swift 1.x where the do-try-catch syntax is not available (only Xcode 7 and Swift 2)
This code has equivalent behavior:
func json_parseData(data: NSData) -> NSDictionary? {
var error: NSError?
// passing the error as inout parameter
// so it can be mutated inside the function (like a pointer reference)
let json: AnyObject? = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.MutableContainerserror: &error)
if error == nil {
print("[JSON] OK!")
return (json as? NSDictionary)
}
print("[ERROR] An error has happened with parsing of json data")
return nil
}
Note: as of Xcode 7 beta 6 you can also use try? which returns nil if an error occurs.