NSLog crashes with certain NSURL- iOS 9.2

Question

Here is my code,where the crash occurs:-

let URL = NSURL(string: "http://files.parsetfss.com/fa80bc63-88d4-412d-a478-2451cffc92a9/tfss-1d2a321d-b02e-4745-a589-e31536f648df-XXXXX%20CAT15%2030.p0001.jpg")
NSLog("Loading page with URL: \(URL)")

The app crashes with EXC_BAD_ACCESS

@MartinR, my bad, I didn't paid too much attention. The URL is kinda truncated for me. It stops exactly before the %20. — mxmlc, Feb 11 '16 at 10:25

Martin R · Accepted Answer · 2016-02-16T12:18:20.847

13

The first argument of NSLog() is a format string, and contains format specifiers (starting with %) which are expanded by the following variable argument list. In your case %20C is a format specifier, but no matching argument is supplied. That causes undefined behavior, it can crash or produce incomplete or wrong output.

If you want to use NSLog() then a general safe method is

NSLog("%@", "Loading page with URL: \(URL)")

In this particular case,

NSLog("Loading page with URL: %@", URL)

works as well, since NSURL is a NSObject subclass and can be used with the %@ format.

edited Feb 16 '16 at 12:18

answered Feb 11 '16 at 10:11

Martin R

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Bull's Eye! Thanks a'lot Martin, didn't knew that %20C is the culprit ;) – Vizllx Feb 11 '16 at 10:41

TechBee · Answer 2 · 2016-02-11T10:08:14.990

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You should use println instead of NSLog.

let URL = NSURL(string: "http://files.parsetfss.com/fa80bc63-88d4-412d-a478-2451cffc92a9/tfss-1d2a321d-b02e-4745-a589-e31536f648df-XXXXX%20CAT15%2030.p0001.jpg")!
println("Loading page with URL: \(URL)")

I have added the option sign ! at the end to unwrap.

edited Feb 11 '16 at 10:08

answered Feb 11 '16 at 10:01

TechBee

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If the OP is using Swift 2.0, `println`has been replaced with `print` – Ollie Feb 11 '16 at 10:17
There can be good reasons to use NSLog even in a Swift program. For example, it does not produce garbage output when called from multiple threads, and it prints a timestamp. – Martin R Feb 11 '16 at 10:18
Is it? I am still using println. it works fine :-) Although thanks for the information @Ollie – TechBee Feb 11 '16 at 10:18
`I am still using println. it works fine` Because you're using Swift 1, not Swift 2. – Eric Aya Feb 11 '16 at 10:28
Thanks for the alternative solution TechBee, but I prefer to use NSLog(), but appreciate your effort +1. – Vizllx Feb 11 '16 at 10:45
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Note that `NSLog` appears in the device log but `print` doesn't. – Timothy Moose Jul 27 '16 at 15:27

NSLog crashes with certain NSURL- iOS 9.2

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