// 获取当前设备可用内存及所占内存的头文件
#import <sys/sysctl.h>
#import <mach/mach.h>

 
 
// 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;
}

// 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;
}