写出方法获取ios内存使用情况。

// 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;

}