1.获取当前设备可用内存(单位：MB）

+ (double)availableMemory {
    vm_statistics_data_t vmStats;
    mach_msg_type_number_t infoCount = HOST_VM_INFO_COUNT;
    kern_return_t kernReturn = host_statistics(mach_host_self(), HOST_VM_INFO, (host_info_t)&vmStats, &infoCount);
    
    if (kernReturn != KERN_SUCCESS) {
        return NSNotFound;
    }
    return ((vm_page_size *vmStats.free_count) / 1024.0) / 1024.0;
}

2.获取当前任务所占用的内存（单位：MB）

+ (double)usedMemory {
    task_basic_info_data_t taskInfo;
    mach_msg_type_number_t infoCount = TASK_BASIC_INFO_COUNT;
    kern_return_t kernReturn = task_info(mach_task_self(),
                                         TASK_BASIC_INFO,
                                         (task_info_t)&taskInfo,
                                         &infoCount);
    if (kernReturn != KERN_SUCCESS ) {
        return NSNotFound;
    }
    return taskInfo.resident_size / 1024.0 / 1024.0;
}

3.获取当前设备的型号

+(NSString*)deviceString
{
    struct utsname systemInfo;
    uname(&systemInfo);
    NSString *deviceString = [NSString stringWithCString:systemInfo.machine encoding:NSUTF8StringEncoding];
    if ([deviceString isEqualToString:@"iPhone1,1"])    return @"iPhone 1G";
    if ([deviceString isEqualToString:@"iPhone1,2"])    return @"iPhone 3G";
    if ([deviceString isEqualToString:@"iPhone2,1"])    return @"iPhone 3GS";
    if ([deviceString isEqualToString:@"iPhone3,1"])    return @"iPhone 4";
    if ([deviceString isEqualToString:@"iPhone4,1"])    return @"iPhone 4S";
    if ([deviceString isEqualToString:@"iPhone5,2"])    return @"iPhone 5";
    if ([deviceString isEqualToString:@"iPhone6,2"])    return @"iPhone 5S";
    if ([deviceString isEqualToString:@"iPhone7,1"])    return @"iPhone 6Plus";    
    if ([deviceString isEqualToString:@"iPhone7,2"])    return @"iPhone 6";
    if ([deviceString isEqualToString:@"iPhone3,2"])    return @"Verizon iPhone 4";
    if ([deviceString isEqualToString:@"iPod1,1"])      return @"iPod Touch 1G";
    if ([deviceString isEqualToString:@"iPod2,1"])      return @"iPod Touch 2G";
    if ([deviceString isEqualToString:@"iPod3,1"])      return @"iPod Touch 3G";
    if ([deviceString isEqualToString:@"iPod4,1"])      return @"iPod Touch 4G";
    if ([deviceString isEqualToString:@"iPad1,1"])      return @"iPad";
    if ([deviceString isEqualToString:@"iPad2,1"])      return @"iPad 2 (WiFi)";
    if ([deviceString isEqualToString:@"iPad2,2"])      return @"iPad 2 (GSM)";
    if ([deviceString isEqualToString:@"iPad2,3"])      return @"iPad 2 (CDMA)";
    if ([deviceString isEqualToString:@"i386"])         return @"Simulator";
    if ([deviceString isEqualToString:@"x86_64"])       return @"Simulator";
    NSLog(@"NOTE: Unknown device type: %@", deviceString);
    return deviceString;
}

4.获取通讯录信息(AddressBook)

+(NSMutableArray*)getAddressBook
{
    NSMutableArray *address_array=[NSMutableArray array];
    
    ABAddressBookRef addressBooks = ABAddressBookCreateWithOptions(NULL, NULL);
    //获取通讯录权限
    
    dispatch_semaphore_t sema = dispatch_semaphore_create(0);
    
    ABAddressBookRequestAccessWithCompletion(addressBooks, ^(bool granted, CFErrorRef error){dispatch_semaphore_signal(sema);});
    
    dispatch_semaphore_wait(sema, DISPATCH_TIME_FOREVER);
    
    CFArrayRef allperson =ABAddressBookCopyArrayOfAllPeople(addressBooks);
    for (id person_record in (__bridge NSArray *)allperson) {
        
        NSMutableArray *phoneNumber_array=[NSMutableArray array];
        
        ABRecordRef person=(__bridge ABRecordRef)(person_record);
        
        //获取个人名字
        CFTypeRef abName = ABRecordCopyValue(person, kABPersonFirstNameProperty);
        CFTypeRef abLastName = ABRecordCopyValue(person, kABPersonLastNameProperty);
        CFStringRef abFullName = ABRecordCopyCompositeName(person);
        NSString *person_name = (__bridge NSString *)abName;
        NSString *lastNameString = (__bridge NSString *)abLastName;
        
        if ((__bridge id)abFullName != nil) {
            
            person_name = (__bridge NSString *)abFullName;
            
        } else {
            if ((__bridge id)abLastName != nil)
            {
                person_name = [NSString stringWithFormat:@"%@ %@", person_name, lastNameString];
            }
        }
       
        ABPropertyID multiProperties[] = {
            kABPersonPhoneProperty,
        };
        ABPropertyID property = multiProperties[0];
        ABMultiValueRef valuesRef = ABRecordCopyValue(person, property);
        NSInteger valuesCount = 0;
        if (valuesRef != nil) valuesCount = ABMultiValueGetCount(valuesRef);
        
        if (valuesCount == 0) {
            CFRelease(valuesRef);
            continue;
        }
        
        //获取电话号码
        for (NSInteger k = 0; k < valuesCount; k++) {
            CFTypeRef value = ABMultiValueCopyValueAtIndex(valuesRef, k);
            NSString *phoneNumber=[NSString stringWithFormat:@"%@",(__bridge NSString*)value];
            NSCharacterSet *numbers = [NSCharacterSet characterSetWithCharactersInString:@"-  ()"];
            phoneNumber = [[phoneNumber componentsSeparatedByCharactersInSet: numbers] componentsJoinedByString:@""];
            phoneNumber=[phoneNumber stringByReplacingOccurrencesOfString:@"+86" withString:@""];
            [phoneNumber_array addObject:phoneNumber];
            CFRelease(value);
        }
        
        UIImage * image=nil;
        //联系人头像
        if(ABPersonHasImageData(person))
        {
            NSData * imageData = (__bridge NSData *)ABPersonCopyImageDataWithFormat(person,kABPersonImageFormatThumbnail);
            image = [[UIImage alloc] initWithData:imageData];
            
        }
        
        CFRelease(valuesRef);
        if([Utils isEmptyString:person_name])
        {
            if(phoneNumber_array.count>0)
            {
                person_name=[phoneNumber_array objectAtIndex:0];
            }
            else
            {
                person_name=@"无号码";
            }
        }
        
        NSString* personName=[NSString stringWithFormat:@"%@",person_name];
        if (abName) CFRelease(abName);
        if (abLastName) CFRelease(abLastName);
        if (abFullName) CFRelease(abFullName);
        
        NSDictionary *dict=@{@"name":personName,@"phoneNumbers":phoneNumber_array,@"invite":@(NO)};
        NSMutableDictionary *m_dict=[NSMutableDictionary dictionaryWithDictionary:dict];
        if(image)
        {
          [m_dict setObject:image forKey:@"image"];
        }
        [address_array addObject:m_dict];
     }
    
     return address_array;
}

5.判断应用是否是第一次启动
在didFinishLaunchingWithOptions方法里添加：

 if !UserDefaults.standard.bool(forKey: "everLaunched") {
      UserDefaults.standard.set(true, forKey: "everLaunched")
      UserDefaults.standard.set(true, forKey: "firstLaunch")
} else {
       UserDefaults.standard.set(false, forKey: "firstLaunch")
}

"everLaunched"判断用户以前是否登录, "firstLaunch" 用来开发者在程序的其他部分判断.
在第一次启动的时候 key "everLaunched" 不会被赋址的, 并且设置为YES. "firstLaunch"被设置为 YES.

在其他代码段进行调用判断：

if UserDefaults.standard.bool(forKey: "firstLaunch") {
    //是第一次启动应用
} else {
   //不是第一次启动应用
}