App crashed when getting string from Dictionary (swift)

Question

I converted a JSON to Dictionary and got some String by

title = json?.objectForKey("Titel_Live") as! String

But some times app will be crashed. I cannot reproduce this problem, just get information from crash reports.

Could someone help me and tell why? Thanks

Error at line 163

Crash reports

Answer 1

title = json?.objectForKey(“Titel_live”) as! String

This line of code where you are doing force unwrapped (Don't force the cast using !) is the cause means if object with key Titel_live dot not find then should be crashed, better go with optional chaining or use gaurd but yes your Json does't contain any object with key Titel_live (may be spelling mistake or object is array so validate once).

//better go like this check if exist or not.
if let t =  json?.objectForKey(“Titel_live”) {
title = t
}

Answer 2

You should not force the casting to String.

You can try :-

title = json?.objectForKey("Title_Live") as? String title = json?.objectForKey("Title_Live") as? String (if title is optional variable) if title is not optional then use:

title = (json?.objectForKey("Title_Live") as? String ?? "")

Because objectForKey will return nil if no value is associated with that key and force casting nil to String fails and causes crash.