CODEWITHSUNDEEP
iosios6ios7linker-errors
pfrank
pfrank

Reputation: 2167

Error when running on iOS 6 but not iOS 7

I am trying to run my project on iOS 6 and I have set all the appropriate build settings to let me do so, but when I run on iOS 6 I get this error:

dyld: Symbol not found: _OBJC_CLASS_$_NSURLSession
  Referenced from: /var/mobile/Applications/8AC09960-A403-413E-B70A-E03DB2AF5844/Flywheel.app/Flywheel
  Expected in: /System/Library/Frameworks/Foundation.framework/Foundation
 in /var/mobile/Applications/8AC09960-A403-413E-B70A-E03DB2AF5844/Flywheel.app/Flywheel

What gives?? iOS 7 works fine.

Upvotes: 4

Views: 3569

Answers (5)

klaudz
klaudz

Reputation: 280

NSURLSession is available above iOS 7. you could find the defination in NSURLSession.h.

NS_CLASS_AVAILABLE(10_9, 7_0)
@interface NSURLSession : NSObject

Please use before checking the system version or checking if this class is available.

if (NSClassFromString(@"NSURLSession") != nil) {
    // available
    // your code
} else {
    // not available
    // other solutions
}

UPDATE

Explanation:

Some friends thought NSClassFromString() is not recommended that I needn't use it here.

I agree to half. Generally, NSClassFromString() is not recommended when using to new a instance or operate a class. But I now use to judge whether the class is available (is nil or not), and I do not produce a class pointer with a string.

I believe that sometimes we can be flexible.

Anyway, if you don't like use NSClassFromString(), I finally found a better way to check if the class is available:

if ([NSURLSession class]) {
    // available
} else {
    // not available
}

Upvotes: -1

Soph
Soph

Reputation: 702

The issue here is that the symbol isn't available on iOS 6. So you have to weak link the Foundation Framework by setting it's status to "optional" in Build Phases -> Link Binary With Libraries.

Upvotes: 16

Simon Germain
Simon Germain

Reputation: 6844

NSURLSession is an iOS7 thing only. You will have to use the good old NSURLConnection with iOS 6, sadly.

Upvotes: 0

rmaddy
rmaddy

Reputation: 318884

NSURLSession was added in iOS 7. Any improper reference to it in your app will cause this problem when run on a device with iOS 6. You need to use proper techniques to ensure the class is never referenced under iOS 6.

Upvotes: 6

pfrank
pfrank

Reputation: 2167

If you're using cocoapods, check your Podfile. It may have 

platform :ios, '7.0'

instead of

platform :ios, '6.0'

Upvotes: 13

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