如何在Xcode 8.1中修复此错误（返回host_statistics）？ 我想知道设备的可用内存

Question

func systemFreeMemorySize() -> UInt?
{
    let HOST_VM_INFO_COUNT: mach_msg_type_number_t = mach_msg_type_number_t(MemoryLayout<vm_statistics_data_t>.size / MemoryLayout<integer_t>.size)

    let host: host_t = mach_host_self()
    var pageSize: vm_size_t = vm_size_t()
    let hostPageSizeKernStatus: kern_return_t = host_page_size(host, &pageSize)
    /*
    guard hostPageSizeKernStatus == KERN_SUCCESS else {
        NSLog("Error with host_page_size(): " + (String.fromCString(mach_error_string(hostPageSizeKernStatus)) ?? "unknown error"))
        return nil
    }*/
    var stats: vm_statistics_data_t = vm_statistics_data_t()
    var count: mach_msg_type_number_t = HOST_VM_INFO_COUNT

    let kernStatus: kern_return_t = withUnsafeMutablePointer(to: &stats) {
        // *** Error on following line:
        return host_statistics(host, HOST_VM_INFO, host_info_t($0), &count)
    }

    /*
    guard kernStatus == KERN_SUCCESS else {
        NSLog("Error with host_statistics(): " + (String.fromCString(mach_error_string(kernStatus)) ?? "unknown error"))
        return nil
    } */

    return UInt(stats.free_count) * UInt(pageSize)
}

在返回host_statistics（host，HOST_VM_INFO，host_info_t（$ 0），＆count）的行中，出现错误：'init'不可用：使用'withMemoryRebound（to：capacity：_）'将内存临时查看为另一种与布局兼容的类型。

如何解决这个问题？

Answer 1

适用于Swift 3.1。 （我添加了更多代码来检查您可能需要的所有信息。）

func freeMemory()->UInt64 {


    let host_port :mach_port_t = mach_host_self()

    let HOST_BASIC_INFO_COUNT = MemoryLayout<host_basic_info>.stride/MemoryLayout<integer_t>.stride
    var size = mach_msg_type_number_t(HOST_BASIC_INFO_COUNT)
    var hostInfo = host_basic_info()

    let status1 = withUnsafeMutablePointer(to: &hostInfo) {
        $0.withMemoryRebound(to: integer_t.self, capacity: Int(size)) {
            host_info(host_port, Int32(HOST_BASIC_INFO), $0, &size)
        }
    }

    print(status1, hostInfo)

    // THE FIX:

    var pageSize: vm_size_t = vm_size_t()
    let hostPageSizeKernStatus: kern_return_t = host_page_size(host_port, &pageSize)


    var vm_stat = vm_statistics_data_t()
    let HOST_VM_INFO_COUNT = MemoryLayout<vm_statistics_data_t>.stride/MemoryLayout<integer_t>.stride
    var size2 = mach_msg_type_number_t(HOST_VM_INFO_COUNT)

    let status2 = withUnsafeMutablePointer(to: &vm_stat) {
        $0.withMemoryRebound(to: integer_t.self, capacity: Int(size2)) {
            host_statistics(host_port, Int32(HOST_VM_INFO), $0, &size2)
            //C:
            //  (void) host_statistics(host_port, HOST_VM_INFO, (host_info_t)&vm_stat, &host_size);

        }
    }

    print(status2, vm_stat)

    let freePages = UInt64(vm_stat.free_count)
    let result = freePages * UInt64(pageSize)


    return result
}

我的MacBook，我得到了：

47483648，cpu_type：7，cpu_subtype：8，cpu_threadtype：1，physical_cpu：4，physical_cpu_max：4，逻辑_cpu：8，逻辑_cpu_max：8，max_mem：17179869184）

vm_statistics（免费计数：1240186，活动计数：1765236，不活动计数：124649，连线计数：684265，零填充计数：921561165，重新激活：4645359，调页：19628659，页面调出：23555，故障：1940619345，cow_faults：94990152，查找次数：2563 purgeable_count：166562，清除：4217152，speculative_count：306146）

其结果是：5079801856即5GB