From iOS 8 we can use the new isOperatingSystemAtLeastVersion method on NSProcessInfo

   NSOperatingSystemVersion ios8_0_1 = (NSOperatingSystemVersion){8, 0, 1};
   if ([[NSProcessInfo processInfo] isOperatingSystemAtLeastVersion:ios8_0_1]) {
      // iOS 8.0.1 and above logic
   } else {
      // iOS 8.0.0 and below logic
   }

Beware that this will crash on iOS 7, as the API didn’t exist prior to iOS 8. If you’re supporting iOS 7 and below, you can safely perform the check with

if ([NSProcessInfo instancesRespondToSelector:@selector(isOperatingSystemAtLeastVersion:)]) {
  // conditionally check for any version >= iOS 8 using 'isOperatingSystemAtLeastVersion'
} else {
  // we're on iOS 7 or below
}

解法2號：

Best current version, without need to deal with numeric search within NSString is to define macros(See original answer: Check iPhone iOS Version)

Those macros do exist in github, see: https://github.com/carlj/CJAMacros/blob/master/CJAMacros/CJAMacros.h

Like this:

#define SYSTEM_VERSION_EQUAL_TO(v)                  ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedSame)
#define SYSTEM_VERSION_GREATER_THAN(v)              ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedDescending)
#define SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(v)  ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] != NSOrderedAscending)
#define SYSTEM_VERSION_LESS_THAN(v)                 ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] == NSOrderedAscending)
#define SYSTEM_VERSION_LESS_THAN_OR_EQUAL_TO(v)     ([[[UIDevice currentDevice] systemVersion] compare:v options:NSNumericSearch] != NSOrderedDescending)

and use them like this:

if (SYSTEM_VERSION_LESS_THAN(@"5.0")) {
    // code here
}

if (SYSTEM_VERSION_GREATER_THAN_OR_EQUAL_TO(@"6.0")) {
    // code here
}

Outdated version below

to get OS version:

[[UIDevice currentDevice] systemVersion]

returns string, which can be turned into int/float via

-[NSString floatValue]
-[NSString intValue]

like this

Both values (floatValue, intValue) will be stripped due to its type, 5.0.1 will become 5.0 or 5 (float or int), for comparing precisely, you will have to separate it to array of INTs check accepted answer here: Check iPhone iOS Version

NSString *ver = [[UIDevice currentDevice] systemVersion];
int ver_int = [ver intValue];
float ver_float = [ver floatValue];

and compare like this

NSLog(@"System Version is %@",[[UIDevice currentDevice] systemVersion]);
NSString *ver = [[UIDevice currentDevice] systemVersion];
float ver_float = [ver floatValue];
if (ver_float < 5.0) return false;

For Swift 4.0 syntax

below example is just checking if the device is of iOS11 or greater version.

let systemVersion = UIDevice.current.systemVersion
if systemVersion.cgFloatValue >= 11.0 {
    //"for ios 11"
  }
else{
   //"ios below 11")
  }

解法3號：

if (NSClassFromString(@"UIPopoverController")) {
    // Do something
}

if ([LAContext class]) {
    // Do something
}

if ([CLLocationManager headingAvailable]) {
    // Do something
}

if (&UIApplicationOpenSettingsURLString != NULL) {
    [[UIApplication sharedApplication] openURL:[NSURL URLWithString:UIApplicationOpenSettingsURLString]];
}

- (BOOL)isOperatingSystemAtLeastVersion:(NSOperatingSystemVersion)version

// A system version of 3.1 or greater is required to use CADisplayLink. The NSTimer
// class is used as fallback when it isn't available.
NSString *reqSysVer = @"3.1";
NSString *currSysVer = [[UIDevice currentDevice] systemVersion];
if ([currSysVer compare:reqSysVer options:NSNumericSearch] != NSOrderedAscending) {
    displayLinkSupported = TRUE;
}

我的解法是，在關閉 picker 的時候，在 完成時再去做 pop alert.

picker.dismiss(animated: true, completion: {
self.present(alertController, animated: true, completion: {
})
})

其他解法：

Found a solution here. I’m probably doing it wrong but if not it might be an Apple bug. The workaround is to delay the presentation of the UIAlertController:

dispatch_async(dispatch_get_main_queue(), ^{
    self.presentViewController(alertController, animated: true, completion: nil)
})

EDIT: I found another workaround (I don’t use the solution I put down here anymore). I had to change this because the Twitter login was also breaking my transitions between VCs.

I now call a specific UIViewController (I called it something like TWLoginVC) where I do all the Twitter login and other stuff. The view is just black so the user don’t see the process is actually done in another VC (he just has to pick up the Twitter user he wants to login with). I guess you could also put a clear background to be even more invisible.

When I call this view controller and dismiss it, the transition is not applied to it and I don’t have any more problem with it.

EDIT Update for Swift:

DispatchQueue.main.async{
     self.present(alertController, animated: true, completion: nil)
}

We can start by instantiating an NSURLSession object with the default session configuration.

Swift

self.urlSession = NSURLSession(configuration: NSURLSessionConfiguration.defaultSessionConfiguration(), delegate: self, delegateQueue: nil)

Objective C

NSURLSessionConfiguration *sessionConfig = [NSURLSessionConfiguration defaultSessionConfiguration];
self.urlSession = [NSURLSession sessionWithConfiguration:sessionConfig delegate:self delegateQueue:nil];

use the dataTaskWithURL:completionHandler: method for the SSL pinning test. The request we send will look something like this:

Swift

self.urlSession?.dataTaskWithURL(NSURL(string:self.urlTextField.text!)!, completionHandler: { (NSData data, NSURLResponse response, NSError error) Void in
    // response management code
}).resume()

Objective C

[[self.urlSession dataTaskWithURL:[NSURL URLWithString:self.textField.text] completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        // response management code
    }] resume];

implemented within the URLSession:didReceiveChallenge:completionHandler:delegatemethod. Note that, upon the creation of the NSURLSession object, we assigned self as the delegate so that this method is called on our object.

Swift

func URLSession(session: NSURLSession,  didReceiveChallenge challenge: NSURLAuthenticationChallenge, completionHandler (NSURLSessionAuthChallengeDisposition, NSURLCredential?) -> Void) {
    let serverTrust = challenge.protectionSpace.serverTrust
    let certificate = SecTrustGetCertificateAtIndex(serverTrust!, 0)

    // Set SSL policies for domain name check
    let policies = NSMutableArray();
    policies.addObject(SecPolicyCreateSSL(true, (challenge.protectionSpace.host)))
    SecTrustSetPolicies(serverTrust!, policies);

    // Evaluate server certificate
    var result: SecTrustResultType = 0
    SecTrustEvaluate(serverTrust!, &result)
    let isServerTrusted:Bool = (Int(result) == kSecTrustResultUnspecified || Int(result) == kSecTrustResultProceed)

    // Get local and remote cert data
    let remoteCertificateData:NSData = SecCertificateCopyData(certificate!)
    let pathToCert = NSBundle.mainBundle().pathForResource(githubCert, ofType: "cer")
    let localCertificate:NSData = NSData(contentsOfFile: pathToCert!)!

    if (isServerTrusted && remoteCertificateData.isEqualToData(localCertificate)) {
        let credential:NSURLCredential = NSURLCredential(forTrust: serverTrust!)
        completionHandler(.UseCredential, credential)
    } else {
        completionHandler(.CancelAuthenticationChallenge, nil)
    }
}

Objective C

-(void)URLSession:(NSURLSession *)session didReceiveChallenge:(NSURLAuthenticationChallenge *)challenge completionHandler:(void (^)(NSURLSessionAuthChallengeDisposition, NSURLCredential * _Nullable))completionHandler {

    // Get remote certificate
    SecTrustRef serverTrust = challenge.protectionSpace.serverTrust;
    SecCertificateRef certificate = SecTrustGetCertificateAtIndex(serverTrust, 0);

    // Set SSL policies for domain name check
    NSMutableArray *policies = [NSMutableArray array];
    [policies addObject:(__bridge_transfer id)SecPolicyCreateSSL(true, (__bridge CFStringRef)challenge.protectionSpace.host)];
    SecTrustSetPolicies(serverTrust, (__bridge CFArrayRef)policies);

    // Evaluate server certificate
    SecTrustResultType result;
    SecTrustEvaluate(serverTrust, &result);
    BOOL certificateIsValid = (result == kSecTrustResultUnspecified || result == kSecTrustResultProceed);

    // Get local and remote cert data
    NSData *remoteCertificateData = CFBridgingRelease(SecCertificateCopyData(certificate));
    NSString *pathToCert = [[NSBundle mainBundle]pathForResource:@"github.com" ofType:@"cer"];
    NSData *localCertificate = [NSData dataWithContentsOfFile:pathToCert];

    // The pinnning check
    if ([remoteCertificateData isEqualToData:localCertificate] && certificateIsValid) {
        NSURLCredential *credential = [NSURLCredential credentialForTrust:serverTrust];
        completionHandler(NSURLSessionAuthChallengeUseCredential, credential);
    } else {
        completionHandler(NSURLSessionAuthChallengeCancelAuthenticationChallenge, NULL);
    }
}

如果不使用 local certificate:

    // Get remote certificate

    SecTrustRef serverTrust = challenge.protectionSpace.serverTrust;

    // Set SSL policies for domain name check

    NSMutableArray *policies = [NSMutableArray array];

    [policies addObject__bridge_transfer id)SecPolicyCreateSSL(true, (__bridge CFStringRef)challenge.protectionSpace.host)];

    SecTrustSetPolicies(serverTrust, (__bridge CFArrayRef)policies);

    // Evaluate server certificate

    SecTrustResultType result;

    SecTrustEvaluate(serverTrust, &result);

    BOOL certificateIsValid = (result == kSecTrustResultUnspecified || result == kSecTrustResultProceed);

    // The pinnning check

    if (certificateIsValid) {

        NSURLCredential *credential = [NSURLCredential credentialForTrust:serverTrust];

        completionHandler(NSURLSessionAuthChallengeUseCredential, credential);

    } else {

        completionHandler(NSURLSessionAuthChallengeCancelAuthenticationChallenge, NULL);

    }

NSString* urlString = @"http://someurl.com/something";
NSURL* url = [NSURL URLWithString:urlString];
NSString* domain = [url host];

Swift 2

var urlString = "http://someurl.com/something"
var url = NSURL(string: urlString)
var domain = url?.host

Swift 3+

var urlString = "http://someurl.com/something"
var url = URL(string: urlString)
var domain = url?.host

I got new error message:

Module compiled with Swift 4.0.3 cannot be imported in Swift 4.1

because AirWatch SDK 18.3 not support xcode 9.3, I try to download and install swift toolchain 4.0.3 from URL:

https://swift.org/download/#releases

Switch toolchain to swift 4.0.3:

and I got new error message with crash:

dyld: Library not loaded: @rpath/libswiftAVFoundation.dylib
 Referenced from: /private/var/containers/Bun

dle/Application/90D24C8C-3ADD-46C7-B57E-4DA9B9B80BFE/AirWatchSDK18.3.app/Frameworks/AWSDK.framework/AWSDK
 Reason: Incompatible library version: AWSDK requires version 1.0.0 or later, but libswiftAVFoundation.dylib provides version 0.0.0

原因是：

Apple states that you can’t mix and match binaries built with different versions of Swift: https://developer.apple.com/swift/blog/?id=2

I have two choices:

• 1: Waiting for new SDK support xcode 9.3
• 2: down-grade to xcode 9.2

Obj-C 的範例：
https://stackoverflow.max-everyday.com/2017/05/open-pdf-documents-in-ios/

Swift 範例：

class ViewController: UIViewController, UIDocumentInteractionControllerDelegate {

    var docController:UIDocumentInteractionController!


    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.

        if let fileURL = NSBundle.mainBundle().pathForResource("SamplePDF1", ofType: "pdf") { // Use if let to unwrap to fileURL variable if file exists
            docController = UIDocumentInteractionController(URL: NSURL(fileURLWithPath: fileURL))

            docController.name = NSURL(fileURLWithPath: fileURL).lastPathComponent

            docController.delegate = self

            docController.presentPreviewAnimated(true)
        }


    }

    func documentInteractionControllerViewControllerForPreview(controller: UIDocumentInteractionController) -> UIViewController {
        return self
    }
     func documentInteractionControllerDidEndPreview(controller: UIDocumentInteractionController) {
        docController = nil
    }

source code:

import UIKit
class ViewController: UIViewController {

    // share text
    @IBAction func shareTextButton(_ sender: UIButton) {

        // text to share
        let text = "This is some text that I want to share."

        // set up activity view controller
        let textToShare = [ text ]
        let activityViewController = UIActivityViewController(activityItems: textToShare, applicationActivities: nil)
        activityViewController.popoverPresentationController?.sourceView = self.view // so that iPads won't crash

        // exclude some activity types from the list (optional)
        activityViewController.excludedActivityTypes = [ UIActivityType.airDrop, UIActivityType.postToFacebook ]

        // present the view controller
        self.present(activityViewController, animated: true, completion: nil)

    }

    // share image
    @IBAction func shareImageButton(_ sender: UIButton) {

        // image to share
        let image = UIImage(named: "Image")

        // set up activity view controller
        let imageToShare = [ image! ]
        let activityViewController = UIActivityViewController(activityItems: imageToShare, applicationActivities: nil)
        activityViewController.popoverPresentationController?.sourceView = self.view // so that iPads won't crash

        // exclude some activity types from the list (optional)
        activityViewController.excludedActivityTypes = [ UIActivityType.airDrop, UIActivityType.postToFacebook ]

        // present the view controller
        self.present(activityViewController, animated: true, completion: nil)
    }

}

執行畫面：

左文字，右圖片。

我的解法很簡單，因為可以透過 String(describing: your_object) 把物件變成字串，所以直接判斷 String 的內容即可。source code:

let preventCopyPaste: Bool? = restrictionsPayloadString.contains("- preventCopyPaste<Bool>: true")

實際上 restrictionsPayload 物件內容：

 restrictionsPayload: 
 Class Type: RestrictionsPayload
 - preventCopyPaste<Bool>: true
 - restrictDocumentToApps<Bool>: true
 - allowedApplications<Array<String>>: []
 - printingEnabled<Bool>: false
 - enableDataLossPrevention<Bool>: true
 - enableWatermark<Bool>: true
 - watermarkOverlay<Optional<String>>: Optional("中華電信 max")
 - preventCustomKeyboards<Bool>: false
 - enableMailComposing<Bool>: false
 - enableLocationReporting<Bool>: true
 - enableDataBackup<Bool>: false
 - enableCameraAccess<Bool>: true

試了以下的解法，完成無作用

modify schema:

In this configuration, if your project build settings does not allow testability in this release mode then setting custom breakpoints or app crashes do not let you debug properly and you are served the fatal error: call of deleted method

Check the project build settings for “testability“.

Ensure it is “Yes” for the build configuration you are testing under.

In my case, I temporarily enabled testability for Release by making it Yes.

from: https://stackoverflow.com/questions/45051325/ios-swift-how-to-debug-sigabrt-fatal-error-call-of-deleted-method-from-a-coc

附上可能有問題的 Object

@objc(AWProfile) public class Profile : NSObject {

    /** @name Generic Profile Information */

    public private(set) var displayName: String?

    public private(set) var comments: String?

    public private(set) var identifier: String?

    public private(set) var organization: String?

    public private(set) var uuid: String?

    public private(set) var version: Int?

    public internal(set) var profileType: AWSDK.AWSDK.ConfigurationProfileType

    public private(set) var isSDKProfile: Bool

    public private(set) var timeStamp: TimeInterval?

    public private(set) var dictionaryToStore: [String : Any]

    /** @name SDK Profile Payloads */

    public private(set) var geofencePayload: AWSDK.GeofencePayload?

    public private(set) var analyticsPayload: AWSDK.AnalyticsPayload?

    public private(set) var restrictionsPayload: AWSDK.RestrictionsPayload?

    public private(set) var compliancePayload: AWSDK.CompliancePayload?

    public private(set) var authenticationPayload: AWSDK.AuthenticationPayload?

    public private(set) var brandingPayload: AWSDK.BrandingPayload?

    public private(set) var breezyPayload: AWSDK.BreezyPayload?

    public private(set) var customPayload: AWSDK.CustomPayload?

    public private(set) var offlineAccessPayload: AWSDK.OfflineAccessPayload?

    public private(set) var networkAccessPayload: AWSDK.NetworkAccessPayload?

    public private(set) var contentFilteringPayload: AWSDK.ContentFilteringPayload?

    public private(set) var websiteFilteringPayload: AWSDK.WebsiteFilteringPayload?

    @objc(initWithInfo:) public init(info: [String : Any])

}

extension Profile {

    @objc public func toDictionary() -> [String : Any]

}

extension Profile {

    @objc override public func isEqual(_ object: Any?) -> Bool

}

extension Profile {

    @objc override public var description: String { get }

}

extension Profile {

    public class func fromData(_ data: Data) -> AWSDK.Profile?

    public func toData() -> Data?

}

@objc(AWRestrictionsPayload) public class RestrictionsPayload : AWSDK.ProfilePayload {

    /** A boolean indicating if Copy and Cut actions are allowed. */

    public fileprivate(set) var preventCopyPaste: Bool

    /** A boolean indicating if Copy and Cut actions are allowed. */

    @available(swift, deprecated: 6.0, message: "preventCopyAndCut is deprecated, use preventCopyPaste instead")

    public fileprivate(set) var preventCopyAndCut: Bool

    /** A boolean indicating whether to only allow open document in allowed list of app */

    public fileprivate(set) var restrictDocumentToApps: Bool

    /** A list of Apps that're allowed to open documents */

    public fileprivate(set) var allowedApplications: [String]

    /** A boolean indicating if printing is allowed. */

    public fileprivate(set) var printingEnabled: Bool

    /** A boolean indicating if data loss prevention is enabled. */

    public fileprivate(set) var enableDataLossPrevention: Bool

    /** A boolean indicating if watermark should be displayed on content that has watermark. */

    public fileprivate(set) var enableWatermark: Bool

    /** The string that indicate the watermark overlay on the content. */

    public fileprivate(set) var watermarkOverlay: String?

    public fileprivate(set) var enableMailComposing: Bool

    public fileprivate(set) var enableLocationReporting: Bool

    public fileprivate(set) var enableDataBackup: Bool

    public fileprivate(set) var enableCameraAccess: Bool

    override public class func payloadType() -> String

}

解法：

updating the Build Setting

Always Embed Swift Standard Libraries to Yes

Try to do clean, build and then run the project.

- (void)hardProcessingWithString:(NSString *)input withCompletion:(void (^)(NSString *result))block;

[object hardProcessingWithString:@"commands" withCompletion:^(NSString *result){
	NSLog(result);
}];

swift 寫法：

func hardProcessingWithString(input: String, completion: (result: String) -> Void) {
	...
	completion("we finished!")
}

加入紅色框框處就做完了，結束，在爸爸的主程式準備一個

    func imageUploadComplete(ret: String) {

        print("Hello:" + ret)

    }

在副程式存取 completion:

completion(dataString!)