获取内存的方法

//加入内存头文件
#import 
#import 

//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;
}