NSError 为 nil 但进入非 nil 状态
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【中文标题】NSError 为 nil 但进入非 nil 状态【英文标题】：NSError is nil but goes into not nil condition 【发布时间】：2015-09-23 18:34:14 【问题描述】：我的应用程序中有这样的代码，它适用于开发配置文件。但是使用 AdHoc 配置文件，当我尝试打印错误时，我的应用程序崩溃了。根据日志，不应该有任何错误，应该为零。但我不知道为什么它满足 if 条件，如果它满足条件，那么如果我尝试打印错误，为什么它会崩溃。另外，此代码在开发配置文件中运行良好。此问题仅与 AdHoc 配置文件有关。 -
func initializedWithCredentials( credentials: GTICredentials!, error: NSError )
// Check to see if initialization was successful. With log i can see that initialization was successful only so there should not be any error
if let error = error as NSError?
// Handle error
NSLog("Error : \(error)") // App Crashes
else
// Success so do something
下面是设备日志——
Incident Identifier: 17FD2BD0-4FA5-492B-891C-2EC066EAFC41
CrashReporter Key: 0fd3245f5726c1a1a90046a6629d5ccc9ebf39dd
Hardware Model: iPhone4,1
Process: VidurOnMobile [2160]
Path: /private/var/mobile/Containers/Bundle/Application/A945905D-C112-4E96-9124-775F4590E5FB/VidurOnMobile.app/VidurOnMobile
Identifier: com.ibm.cio.be.iphone.VidurOnMobile
Version: 1 (1.0)
Code Type: ARM (Native)
Parent Process: launchd [1]
Date/Time: 2015-09-22 22:25:45.149 +0530
Launch Time: 2015-09-22 22:25:01.041 +0530
OS Version: ios 8.4.1 (12H321)
Report Version: 104
Exception Type: EXC_BAD_ACCESS (SIGSEGV)
Exception Subtype: KERN_INVALID_ADDRESS at 0x00000000
Triggered by Thread: 0
Thread 0 name: Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0 CoreFoundation 0x2a8bf0d6 0x2a89c000 + 143574
1 libswiftCore.dylib 0x00962960 0x886000 + 903520
2 libswiftCore.dylib 0x00943160 0x886000 + 774496
3 VidurOnMobile 0x00107728 0xea000 + 120616
4 VidurOnMobile 0x00109df8 0xea000 + 130552
5 libdispatch.dylib 0x393c9c80 0x393c8000 + 7296
6 libdispatch.dylib 0x393c9c6c 0x393c8000 + 7276
7 libdispatch.dylib 0x393d554e 0x393c8000 + 54606
8 CoreFoundation 0x2a96c664 0x2a89c000 + 853604
9 CoreFoundation 0x2a96ad84 0x2a89c000 + 847236
10 CoreFoundation 0x2a8b66cc 0x2a89c000 + 108236
11 CoreFoundation 0x2a8b64de 0x2a89c000 + 107742
12 GraphicsServices 0x3227b1a4 0x32272000 + 37284
13 UIKit 0x2e068440 0x2dff9000 + 455744
14 VidurOnMobile 0x000fa62e 0xea000 + 67118
15 libdyld.dylib 0x39407aac 0x39406000 + 6828
Thread 1 name: Dispatch queue: com.apple.libdispatch-manager
Thread 1:
0 libsystem_kernel.dylib 0x394ba24c 0x394b9000 + 4684
1 libdispatch.dylib 0x393da4ec 0x393c8000 + 74988
2 libdispatch.dylib 0x393da21e 0x393c8000 + 74270
Thread 2:
0 libsystem_kernel.dylib 0x394ce9c0 0x394b9000 + 88512
1 libsystem_pthread.dylib 0x3954be14 0x3954b000 + 3604
2 libsystem_pthread.dylib 0x3954baec 0x3954b000 + 2796
Thread 3 name: Dispatch queue: com.apple.root.default-qos.overcommit
Thread 3:
0 CoreFoundation 0x2a8aa348 0x2a89c000 + 58184
1 CoreFoundation 0x2a9dbc2c 0x2a89c000 + 1309740
2 CoreFoundation 0x2a8aa344 0x2a89c000 + 58180
3 libobjc.A.dylib 0x38e541a4 0x38e33000 + 135588
4 libdispatch.dylib 0x393d69b4 0x393c8000 + 59828
5 libdispatch.dylib 0x393d789e 0x393c8000 + 63646
6 libsystem_pthread.dylib 0x3954bd9a 0x3954b000 + 3482
7 libsystem_pthread.dylib 0x3954baec 0x3954b000 + 2796
Thread 4:
0 libsystem_kernel.dylib 0x394ce9c0 0x394b9000 + 88512
1 libsystem_pthread.dylib 0x3954be14 0x3954b000 + 3604
2 libsystem_pthread.dylib 0x3954baec 0x3954b000 + 2796
Thread 5 name: Dispatch queue: com.apple.CFNetwork.addPersistCacheToStorageDaemon
Thread 5:
0 libsystem_kernel.dylib 0x394ba49c 0x394b9000 + 5276
1 libsystem_kernel.dylib 0x394ba290 0x394b9000 + 4752
2 libdispatch.dylib 0x393dae1a 0x393c8000 + 77338
3 libdispatch.dylib 0x393dab46 0x393c8000 + 76614
4 libxpc.dylib 0x39560ea6 0x39560000 + 3750
5 Foundation 0x2b7a98fa 0x2b617000 + 1648890
6 Foundation 0x2b7a8f6e 0x2b617000 + 1646446
7 Foundation 0x2b62abea 0x2b617000 + 80874
8 CoreFoundation 0x2a9aa30c 0x2a89c000 + 1106700
9 CoreFoundation 0x2a8d9704 0x2a89c000 + 251652
10 CFNetwork 0x2a462e98 0x2a3d4000 + 585368
11 CFNetwork 0x2a43179c 0x2a3d4000 + 382876
12 libdispatch.dylib 0x393c9c80 0x393c8000 + 7296
13 libdispatch.dylib 0x393d44ce 0x393c8000 + 50382
14 libdispatch.dylib 0x393d3d9c 0x393c8000 + 48540
15 libdispatch.dylib 0x393d648e 0x393c8000 + 58510
16 libdispatch.dylib 0x393d789e 0x393c8000 + 63646
17 libsystem_pthread.dylib 0x3954bd9a 0x3954b000 + 3482
18 libsystem_pthread.dylib 0x3954baec 0x3954b000 + 2796
Thread 6 name: WebThread
Thread 6:
0 libsystem_kernel.dylib 0x394ba49c 0x394b9000 + 5276
1 libsystem_kernel.dylib 0x394ba290 0x394b9000 + 4752
2 CoreFoundation 0x2a96c5ce 0x2a89c000 + 853454
3 CoreFoundation 0x2a96ab94 0x2a89c000 + 846740
4 CoreFoundation 0x2a8b66cc 0x2a89c000 + 108236
5 CoreFoundation 0x2a8b64de 0x2a89c000 + 107742
6 WebCore 0x36723d2c 0x366a2000 + 531756
7 libsystem_pthread.dylib 0x3954dddc 0x3954b000 + 11740
8 libsystem_pthread.dylib 0x3954dd4e 0x3954b000 + 11598
9 libsystem_pthread.dylib 0x3954baf8 0x3954b000 + 2808
Thread 7 name: javascriptCore::BlockFree
Thread 7:
0 libsystem_kernel.dylib 0x394cdb2c 0x394b9000 + 84780
1 libsystem_pthread.dylib 0x3954d354 0x3954b000 + 9044
2 libsystem_pthread.dylib 0x3954e224 0x3954b000 + 12836
3 libc++.1.dylib 0x38600fa4 0x385fb000 + 24484
4 JavaScriptCore 0x2bbd3206 0x2bbbe000 + 86534
5 JavaScriptCore 0x2bbcf6bc 0x2bbbe000 + 71356
6 libsystem_pthread.dylib 0x3954dddc 0x3954b000 + 11740
7 libsystem_pthread.dylib 0x3954dd4e 0x3954b000 + 11598
8 libsystem_pthread.dylib 0x3954baf8 0x3954b000 + 2808
Thread 8 name: JavaScriptCore::Marking
Thread 8:
0 libsystem_kernel.dylib 0x394cdb2c 0x394b9000 + 84780
1 libsystem_pthread.dylib 0x3954d354 0x3954b000 + 9044
2 libsystem_pthread.dylib 0x3954e224 0x3954b000 + 12836
3 libc++.1.dylib 0x38600fa4 0x385fb000 + 24484
4 JavaScriptCore 0x2bd98140 0x2bbbe000 + 1941824
5 JavaScriptCore 0x2bd981a4 0x2bbbe000 + 1941924
6 JavaScriptCore 0x2bbcf6bc 0x2bbbe000 + 71356
7 libsystem_pthread.dylib 0x3954dddc 0x3954b000 + 11740
8 libsystem_pthread.dylib 0x3954dd4e 0x3954b000 + 11598
9 libsystem_pthread.dylib 0x3954baf8 0x3954b000 + 2808
Thread 9 name: com.apple.NSURLConnectionLoader
Thread 9:
0 libsystem_kernel.dylib 0x394ba49c 0x394b9000 + 5276
1 libsystem_kernel.dylib 0x394ba290 0x394b9000 + 4752
2 CoreFoundation 0x2a96c5ce 0x2a89c000 + 853454
3 CoreFoundation 0x2a96ab94 0x2a89c000 + 846740
4 CoreFoundation 0x2a8b66cc 0x2a89c000 + 108236
5 CoreFoundation 0x2a8b64de 0x2a89c000 + 107742
6 CFNetwork 0x2a451422 0x2a3d4000 + 513058
7 Foundation 0x2b6e7186 0x2b617000 + 852358
8 libsystem_pthread.dylib 0x3954dddc 0x3954b000 + 11740
9 libsystem_pthread.dylib 0x3954dd4e 0x3954b000 + 11598
10 libsystem_pthread.dylib 0x3954baf8 0x3954b000 + 2808
Thread 10:
0 libsystem_kernel.dylib 0x394ce9c0 0x394b9000 + 88512
1 libsystem_pthread.dylib 0x3954be14 0x3954b000 + 3604
2 libsystem_pthread.dylib 0x3954baec 0x3954b000 + 2796
Thread 11:
0 libsystem_kernel.dylib 0x394ce9c0 0x394b9000 + 88512
1 libsystem_pthread.dylib 0x3954be14 0x3954b000 + 3604
2 libsystem_pthread.dylib 0x3954baec 0x3954b000 + 2796
Thread 12 name: com.apple.CFSocket.private
Thread 12:
0 libsystem_kernel.dylib 0x394ce080 0x394b9000 + 86144
1 CoreFoundation 0x2a970d80 0x2a89c000 + 871808
2 libsystem_pthread.dylib 0x3954dddc 0x3954b000 + 11740
3 libsystem_pthread.dylib 0x3954dd4e 0x3954b000 + 11598
4 libsystem_pthread.dylib 0x3954baf8 0x3954b000 + 2808
Thread 0 crashed with ARM Thread State (32-bit):
r0: 0x00000000 r1: 0x00000000 r2: 0x00000000 r3: 0x00000004
r4: 0x00000000 r5: 0x00000000 r6: 0x00d416c0 r7: 0x00884c44
r8: 0x1768cf00 r9: 0x175b8774 r10: 0x00884cf0 r11: 0x3bded0e0
ip: 0x0068c2e0 sp: 0x00884c18 lr: 0x00962964 pc: 0x2a8bf0d6
cpsr: 0x60000030
【问题讨论】：
从函数的定义来看，error不能为nil。错误：NSError error 是可选的，因此它可以是 nil 或一些错误。在这种情况下，不应该有任何错误，应该进入 else 条件，但它会进入 if 条件，如果尝试打印错误也会崩溃。此外，此问题仅与 AdHoc 配置文件有关。 【参考方案1】：如果函数的定义是错误的，则错误永远不能为零：NSError。如果错误可能为零，则应将其定义为错误：NSError？。否则，尝试解开非可选值是没有意义的。它应该是这样的：
func initializedWithCredentials(credentials: GTICredentials!, error: NSError? )
if let error = error
// Handle error
NSLog("Error : \(error)")
else
// Success so do something
更好的是，你应该避免嵌套 if 条件
func initializedWithCredentials(credentials: GTICredentials!, error: NSError? )
if let error = error
// Handle error
NSLog("Error : \(error)")
return
// Success so do something
【讨论】：
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