How to get Wifi SSID in iOS9 after CaptiveNetwork is deprecated and calls for Wifi name are already blocked

Register your app as Hotspot helper.

#import <NetworkExtension/NetworkExtension.h>  

NSArray * networkInterfaces = [NEHotspotHelper supportedNetworkInterfaces];  
NSLog(@"Networks %@",networkInterfaces);  

UPDATE (Sept. 11th, 2015)

The following Captive Network APIs have been re-enabled in the latest version of iOS 9 instead.

• CNCopySupportedInterfaces
• CNCopyCurrentNetworkInfo

UPDATE (Sept. 16th, 2015)

If you still prefer to use NetworkExtension and Apple gave you permission to add the entitlements, then you can do this to get the wifi information:

for(NEHotspotNetwork *hotspotNetwork in [NEHotspotHelper supportedNetworkInterfaces]) {
    NSString *ssid = hotspotNetwork.SSID;
    NSString *bssid = hotspotNetwork.BSSID;
    BOOL secure = hotspotNetwork.secure;
    BOOL autoJoined = hotspotNetwork.autoJoined;
    double signalStrength = hotspotNetwork.signalStrength;
}

NetworkExtension provides you some extra information as secure, auto joined or the signal strength. And it also allows you to set credential to wifis on background mode, when the user scans wifis around.

In the GM for iOS 9, it seems like this is enabled again. In fact, it's not even listed as deprecated in the online documentation, however the CaptiveNetwork header file does have the following:

CNCopySupportedInterfaces (void) __OSX_AVAILABLE_BUT_DEPRECATED_MSG(__MAC_10_8, __MAC_NA, __IPHONE_4_1, __IPHONE_9_0, CN_DEPRECATION_NOTICE);

So, it is working in the iOS 9 GM, but not sure for how long :)

The answer by abdullahselek is still correct even for Swift 4.1 and 4.2.

A small caveat is that now in iOS 12, you must go to the capabilities section of your app project and enable the Access WiFi Information feature. It will add an entitlement entry to your project and allow the function call CNCopyCurrentNetworkInfo to work properly.

If you do not do this, that function simply returns nil. No errors or warnings at runtime about the missing entitlement will be displayed.

For more info, see the link below to Apple's documentation.

https://developer.apple.com/documentation/systemconfiguration/1614126-cncopycurrentnetworkinfo