public function sum(number1:Number,number2:Number):Number{
       // call C function sum with 2 arguments, number 1 and number2 and return a value
	var ret:Number = context.call("sum",number1,number2) as Number;
	return ret;
}

FREObject sum(FREContext ctx, void* funcData, uint32_t argc, FREObject argv[]){
    // argc ... argument count, uint
    // argv ... argument values, Array
 
    // retrieve first argument and write it to a variable
    double number1;
    FREGetObjectAsDouble(argv[0], &number1);
 
    // retrieve second argument and write it to a variable
    double number2;
    FREGetObjectAsDouble(argv[1], &number2);
 
    // add first and second number together
    double sum = number1 + number2;
 
    // write computed sum to FREObject that will be returned back to AS3
    FREObject sumToReturn = nil;
    FRENewObjectFromDouble(sum, &sumToReturn);
 
    return sumToReturn;
}

public function subtract(int1:int,int2:int):int{
	var ret:Number = context.call("subtract",int1,int2) as int;
	return ret;
}

FREObject subtract(FREContext ctx, void* funcData, uint32_t argc, FREObject argv[]){
    int32_t int1;
    FREGetObjectAsInt32(argv[0], &int1);
 
    int32_t int2;
    FREGetObjectAsInt32(argv[1], &int2);
 
    int32_t sum = int1 - int2;
 
    NSLog(@"%d-%d=%d",int1,int2,sum);
 
    FREObject sumToReturn = nil;
    FRENewObjectFromInt32(sum, &sumToReturn);
 
    return sumToReturn;
}

public function multiply(uint1:uint,uint2:uint):uint{
	var ret:Number = context.call("multiply",uint1,uint2) as uint;
	return ret;
}

FREObject multiply(FREContext ctx, void* funcData, uint32_t argc, FREObject argv[]){
    uint32_t uint1;
    FREGetObjectAsUint32(argv[0], &uint1);
 
    uint32_t uint2;
    FREGetObjectAsUint32(argv[1], &uint2);
 
    uint32_t sum = uint1*uint2;
 
    NSLog(@"%d*%d=%d",uint1,uint2,sum);
 
    FREObject sumToReturn = nil;
    FRENewObjectFromUint32(sum, &sumToReturn);
 
    return sumToReturn;
}

public function concatenate(str1:String,str2:String):String{
	var ret:String = context.call("concatenate",str1,str2) as String;
	return ret;
}

FREObject concatenate(FREContext ctx, void* funcData, uint32_t argc, FREObject argv[]){
    // To be filled
    uint32_t string1Length;
    const uint8_t *string1;
    FREGetObjectAsUTF8(argv[0], &string1Length, &string1);
 
    uint32_t string2Length;
    const uint8_t *string2;
    FREGetObjectAsUTF8(argv[1], &string2Length, &string2);
 
    // Convert C strings to Obj-C strings
    NSString *string1ObjC = [NSString stringWithUTF8String:(char*)string1];
    NSString *string2ObjC = [NSString stringWithUTF8String:(char*)string2];
 
    // Concat strings
    NSString *returnString = [string1ObjC stringByAppendingString:string2ObjC];
 
    // Convert Obj-C string to C UTF8String
    const char *str = [returnString UTF8String];
 
    // Prepare for AS3
    FREObject retStr;
	FRENewObjectFromUTF8(strlen(str)+1, (const uint8_t*)str, &retStr);
 
    // Return data back to ActionScript
	return retStr;
}

public function opposite(bool:Boolean):Boolean{
	var ret:Boolean = context.call("opposite",bool) as Boolean;
	return ret;
}

FREObject opposite(FREContext ctx, void* funcData, uint32_t argc, FREObject argv[]){
    uint32_t boolean;
    FREGetObjectAsBool(argv[0], &boolean);
 
    uint32_t oppositeValue = !boolean;
 
    FREObject retBool = nil;
    FRENewObjectFromBool(oppositeValue, &retBool);
 
    return retBool;   
}

unzip -o IOSExtension.swc
 
/PATH/TO/FLEX_AIR_SDK/bin/adt -package -target ane IOSExtension.ane extension.xml -swc IOSExtension.swc -platform iPhone-ARM library.swf libIOSExtension.a

<extension xmlns="http://ns.adobe.com/air/extension/2.5">
    <id>com.krcha.IOSExtension</id>
    <versionNumber>1</versionNumber>
    <platforms>
      <platform name="iPhone-ARM">
        <applicationDeployment>
          <nativeLibrary>libIOSExtension.a</nativeLibrary>
          <initializer>ADBEExtInitializer</initializer>
          <finalizer>ADBEExtFinalizer</finalizer>
        </applicationDeployment>
      </platform>
    </platforms>
</extension>