一、引入头文件

#import <sys/sysctl.h>
#import <mach/mach.h>
#import <malloc/malloc.h>

二、实现方法

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;
}

//获取实例对象的成员变量所占用的内存大小（单位：KB）

+ (double)usedMemoryWithObject:(NSObject *)object
{
    return class_getInstanceSize([object class]) / 1024.0;
}