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

Don't force the cast. You should never use `!` when parsing JSON. — Aaron Brager, Jul 28 '16 at 13:23
I think your response don't have the data with `key == Titel_Live ` — iSashok, Jul 28 '16 at 13:23
Is there other reason? Because the String "Titel_Live" seems to be always there, didn't changed — shilei365, Jul 29 '16 at 08:17

Buntylm · Accepted Answer · 2016-07-28T13:37:15.623

4

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
}

edited Jul 28 '16 at 13:37

answered Jul 28 '16 at 13:29

Buntylm

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Is there other reason? Because the String "Titel_Live" seems to be always there, didn't changed. – shilei365 Jul 29 '16 at 08:05
may be it is there but not as dictionary. currently you are trying to get object for key. – Buntylm Jul 29 '16 at 09:17

score 2 · Answer 2 · edited Jul 28 '16 at 13:41

2

You should not force the casting to String.

You can try :-

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.

edited Jul 28 '16 at 13:41

swiftBoy

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answered Jul 28 '16 at 13:36

Pavan gopal

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4

App crashed when getting string from Dictionary (swift)

2 Answers2