/* Get the set of input ports that are available for routing. Note that this property only applies to the session's current category and mode.

   For example, if the session's current category is AVAudioSessionCategoryPlayback, there will be no available inputs. */

@property(readonly) NSArray * availableInputs NS_AVAILABLE_IOS(7_0); /* NSArray of AVAudioSessionPortDescription objects. */

/* Select a preferred input port for audio routing. If the input port is already part of the current audio route, this will have no effect.

   Otherwise, selecting an input port for routing will initiate a route change to use the preferred input port, provided that the application's

   session controls audio routing. */

- (BOOL) setPreferredInput:(AVAudioSessionPortDescription*)inPort error:(NSError **)outError NS_AVAILABLE_IOS(7_0);

/* Array of AVAudioSessionDataSourceDescription objects. Will be nil if there are no selectable data sources. */

@property(readonly) NSArray *	dataSources NS_AVAILABLE_IOS(7_0);

/* Select the preferred data source for this port. The input dataSource parameter must be one of the dataSources exposed by the dataSources property.

Note: if the port is part of the active audio route, changing the data source will likely

result in a route reconfiguration. If the port is not part of the active route, selecting a new data source will

not result in an immediate route reconfiguration. Use AVAudioSession's setPreferredInput:error: method to activate the port. */

- (BOOL) setPreferredDataSource:(AVAudioSessionDataSourceDescription *)dataSource error:(NSError **)outError NS_AVAILABLE_IOS(7_0);

/* Array of one or more NSStrings describing the supported polar patterns for a data source. Will be nil for data sources that have no selectable patterns. */

@property(readonly) NSArray *	supportedPolarPatterns NS_AVAILABLE_IOS(7_0);

/* Select the desired polar pattern from the set of available patterns. Note: if the owning port and data source are part of the active audio route,

   changing the polar pattern will likely result in a route reconfiguration. If the owning port and data source are not part of the active route,

   selecting a polar pattern will not result in an immediate route reconfiguration. Use AVAudioSession's setPreferredInput:error: method

   to activate the port. Use setPreferredDataSource:error: to active the data source on the port. */

- (BOOL) setPreferredPolarPattern:(NSString *)pattern error:(NSError **)outError NS_AVAILABLE_IOS(7_0);

#import <AVFoundation/AVAudioSession.h>

- (void) demonstrateInputSelection

{

    NSError* theError = nil;

    BOOL result = YES;

    AVAudioSession* myAudioSession = [AVAudioSession sharedInstance];

    result = [myAudioSession setCategory:AVAudioSessionCategoryPlayAndRecord error:&theError];

    if (!result)

    {

        NSLog(@"setCategory failed");

    }

    result = [myAudioSession setActive:YES error:&theError];

    if (!result)

    {

        NSLog(@"setActive failed");

    }

    // Get the set of available inputs. If there are no audio accessories attached, there will be

    // only one available input -- the built in microphone.

    NSArray* inputs = [myAudioSession availableInputs];

    // Locate the Port corresponding to the built-in microphone.

    AVAudioSessionPortDescription* builtInMicPort = nil;

    for (AVAudioSessionPortDescription* port in inputs)

    {

        if ([port.portType isEqualToString:AVAudioSessionPortBuiltInMic])

        {

            builtInMicPort = port;

            break;

        }

    }

    // Print out a description of the data sources for the built-in microphone

    NSLog(@"There are %u data sources for port :\"%@\"", (unsigned)[builtInMicPort.dataSources count], builtInMicPort);

    NSLog(@"%@", builtInMicPort.dataSources);

    // loop over the built-in mic's data sources and attempt to locate the front microphone

    AVAudioSessionDataSourceDescription* frontDataSource = nil;

    for (AVAudioSessionDataSourceDescription* source in builtInMicPort.dataSources)

    {

        if ([source.orientation isEqual:AVAudioSessionOrientationFront])

        {

            frontDataSource = source;

            break;

        }

    } // end data source iteration

    if (frontDataSource)

    {

        NSLog(@"Currently selected source is \"%@\" for port \"%@\"", builtInMicPort.selectedDataSource.dataSourceName, builtInMicPort.portName);

        NSLog(@"Attempting to select source \"%@\" on port \"%@\"", frontDataSource, builtInMicPort.portName);

        // Set a preference for the front data source.

        theError = nil;

        result = [builtInMicPort setPreferredDataSource:frontDataSource error:&theError];

        if (!result)

        {

            // an error occurred. Handle it!

            NSLog(@"setPreferredDataSource failed");

        }

    }

    // Make sure the built-in mic is selected for input. This will be a no-op if the built-in mic is

    // already the current input Port.

    theError = nil;

    result = [myAudioSession setPreferredInput:builtInMicPort error:&theError];

    if (!result)

    {

        // an error occurred. Handle it!

        NSLog(@"setPreferredInput failed");

    }

}

There are 3 data sources for port :"<AVAudioSessionPortDescription: 0x14d935a0, type = MicrophoneBuiltIn; name = iPhone Microphone; UID = Built-In Microphone; selectedDataSource = Bottom>"

(

    "<AVAudioSessionDataSourceDescription: 0x14d93800, ID = 1835216945; name = Bottom>",

    "<AVAudioSessionDataSourceDescription: 0x14d938d0, ID = 1835216946; name = Front>",

    "<AVAudioSessionDataSourceDescription: 0x14d93a10, ID = 1835216947; name = Back>"

)

Currently selected source is "Bottom" for port "iPhone Microphone"

Attempting to select source "<AVAudioSessionDataSourceDescription: 0x14d938d0, ID = 1835216946; name = Front>" on port "iPhone Microphone”