ios - message sent to deallocated instance

完整报错如下：
-[CFString isEqualToString:]message sent to deallocated instance

代码如下：

 dispatch_async(self.queue, ^{
        if ([RAUtility isUploadHost:request]) {
            return;
        }
       .............//后面还有一部分代码
    });

+ (BOOL)isUploadHost:(NSURLRequest *)request {
    if (!request) {
        return NO;
    }
    // 去掉尾部'/'再进行比较
    NSString *requestURLString = request.URL.absoluteString;
    NSString *testAddress = [APM getTestUploadAddress];
    BOOL isUploadHost = [requestURLString isEqualToString:testAddress] ||
    [requestURLString isEqualToString:APM_UPLOADADDRESS];
    
    return isUploadHost;
}

崩溃出现在

BOOL isUploadHost = [requestURLString isEqualToString:testAddress] ||
    [requestURLString isEqualToString:RichAPM_UPLOADADDRESS];"
    
开启僵尸检测xode 日志如下：

*** -[CFString isEqualToString:]: message sent to deallocated instance 0x101393e00


 po requestURLString
2017-02-20 15:27:15.448664 Browser[4170:294768] *** -[CFString respondsToSelector:]: message sent to deallocated instance 0x101393e00
class name = _NSZombie_CFString

po request.URL.absoluteString
https://m.baidu.com/tc?tcreq4log=1&ssid=0&from=844b&pu=sz%401320_2001%2Cta%40iphone_1_10.2_3_602&qid=9501293810319954737&ct=10&cst=4&ref=index_iphone&lid=9501293810319954737&w=0_0_&sid=114455_102568_104496_100183_102478_106371_107324_109550_114000_110313_107918_112107_107315_112135_114125_114077_114512_114329_114534_114202_114313_112093_114276_114718_110085&rids=13115399611138481457&pos=13&clk_from=mid_news&stype=&extra=%7B%22category%22:0,%22cb_lr_expid%22:0,%22cb_lr_score%22:0,%22cb_manual_score%22:0,%22channel_id%22:0,%22click%22:9328,%22coverquality%22:0,%22cs%22:%22%22,%22flag%22:1,%22genre%22:0,%22index_expid%22:0,%22label%22:%5B%5D,%22live_type%22:0,%22mark%22:6,%22mark_rec%22:6,%22mthid%22:%22-1%22,%22rec_src%22:%5B9%5D,%22score%22:42118.4,%22show%22:96974,%22source%22:0,%22srccat%22:0,%22steplength%22:-1,%22top%22:0,%22type%22:0%7D&logExtra=%7B%22st%22:%22video%22,%22source%22:%22small_video%22,%22extra%22:%22%7B%5C%22category%5C%22:0,%5C%22cb_lr_expid%5C%22:0,%5C%22cb_lr_score%5C%22:0,%5C%22cb_manual_score%5C%22:0,%5C%22channel_id%5C%22:0,%5C%22click%5C%22:9328,%5C%22coverquality%5C%22:0,%5C%22cs%5C%22:%5C%22%5C%22,%5C%22flag%5C%22:1,%5C%22genre%5C%22:0,%5C%22index_expid%5C%22:0,%5C%22label%5C%22:%5B%5D,%5C%22live_type%5C%22:0,%5C%22mark%5C%22:6,%5C%22mark_rec%5C%22:6,%5C%22mthid%5C%22:%5C%22-1%5C%22,%5C%22rec_src%5C%22:%5B9%5D,%5C%22score%5C%22:42118.4,%5C%22show%5C%22:96974,%5C%22source%5C%22:0,%5C%22srccat%5C%22:0,%5C%22steplength%5C%22:-1,%5C%22top%5C%22:0,%5C%22type%5C%22:0%7D%22,%22stype%22:null,%22rid%22:%2213115399611138481457%22,%22pos%22:13,%22picNum%22:1,%22title%22:%22%5Cu53f0%5Cu6e7e%5Cu6700%5Cu65b0%5Cu6027%5Cu6559%5Cu80b2%5Cu77ed%5Cu7247%20%5Cu7edd%5Cu5bf9%5Cu9707%5Cu64bc%5Cu5fc3%5Cu7075%22%7D&r=1487575566391

堆栈信息

(lldb) bt
* thread #12: tid = 0x47f70, 0x000000018a1951c4 CoreFoundation`___forwarding___ + 744, queue = 'com.rich.RichNetworkRecorder', stop reason = EXC_BREAKPOINT (code=1, subcode=0x18a1951c4)
    frame #0: 0x000000018a1951c4 CoreFoundation`___forwarding___ + 744
  * frame #1: 0x000000018a08e80c CoreFoundation`_CF_forwarding_prep_0 + 92
    frame #2: 0x000000010012f580 Browser`+[RAUtility isUploadHost:](self=RAUtility, _cmd="isUploadHost:", request=0x0000000170209840) + 220 at RAUtility.m:24
    frame #3: 0x000000010011a36c Browser`__105-[RANetworkRecorder recordRequestWillBeSentWithRequestID:request:redirectResponse:class:selector:thread:]_block_invoke((null)=) + 64 at RANetworkRecorder.m:73
    frame #4: 0x000000010035d258 libdispatch.dylib`_dispatch_call_block_and_release + 24
    frame #5: 0x000000010035d218 libdispatch.dylib`_dispatch_client_callout + 16
    frame #6: 0x000000010036aaec libdispatch.dylib`_dispatch_queue_serial_drain + 1136
    frame #7: 0x0000000100360ce0 libdispatch.dylib`_dispatch_queue_invoke + 672
    frame #8: 0x000000010036ce2c libdispatch.dylib`_dispatch_root_queue_drain + 584
    frame #9: 0x000000010036cb78 libdispatch.dylib`_dispatch_worker_thread3 + 140
    frame #10: 0x00000001892232a0 libsystem_pthread.dylib`_pthread_wqthread + 1288
    frame #11: 0x0000000189222d8c libsystem_pthread.dylib`start_wqthread + 4
  
想问如下问题：
1.po 为何可以打印request.URL.absoluteString的值而不能打印requestURLString，requestURLString不是指向request.URL.absoluteString？
2.我查了下，request 对url 是copy，URL 对absoluteString又是copy,是不是可以说明是request被释放了？
3.但是po仍然可以打印出request，
(lldb) po request
 { URL: https://m.baidu.com/tc?
4.你觉得可能哪里出了问题，该怎么修复？