Comparing two identical string, but they are evaluated as false

Question

I am trying to have a certain block of code only be executed if the users iPhone is of a certain model. I am testing on the iOS Simulator, so I used the iPhoneModel() function bellow to get the device model for the simulator and printed it to the console and pasted it into the if condition in the compare() function.

func iPhoneModel() -> String {
    var sysinfo = utsname()
    uname(&sysinfo) // ignore return value
    return NSString(bytes: &sysinfo.machine, length: Int(_SYS_NAMELEN), encoding: NSASCIIStringEncoding)! as String
}

func compare() {
    if iPhoneModel() == "x86_64" {
        print("It Worked!")
    }
}

The iPhoneModel() function should return an identical string and the statement should be true, but instead it is false. I have even printed both strings to console to check them with my own eyes and they both appear to be identical, yet the computer thinks otherwise. Any ideas why?

Can you use a debugger to step thorough the code one by one? — Luka Jacobowitz, Apr 13 '16 at 19:21
Print lengths of both strings to make sure there's no trailing whitespace in there. — Sergey Kalinichenko, Apr 13 '16 at 19:22
Also maybe convert the NSString to a regular string before comparing — Luka Jacobowitz, Apr 13 '16 at 19:26
_SYS_NAMELEN == 256 is buffer size in `struct utsname`, not the actual size of the string. Therefore the returned string has a bunch of trailing NUL characters. – Have a look at http://stackoverflow.com/questions/26028918/ios-how-to-determine-iphone-model-in-swift for various working methods. — Martin R, Apr 13 '16 at 19:33

score 0 · Accepted Answer · answered Apr 13 '16 at 20:43

I think you could just strip out the null characters...

func iPhoneModel() -> String {
    var sysinfo = utsname()
    uname(&sysinfo) // ignore return value

    var iPhoneModel = NSString(bytes: &sysinfo.machine, length: Int(_SYS_NAMELEN), encoding: NSASCIIStringEncoding)! as String

    iPhoneModel = iPhoneModel.stringByReplacingOccurrencesOfString("\0", withString: "", options: NSStringCompareOptions.LiteralSearch, range: nil)

    return iPhoneModel
}

Comparing two identical string, but they are evaluated as false

1 Answers1