(转)ios error:unrecognized selector sent to class
转自:http://blog.itpub.net/12231606/viewspace-1081952/
今天将app统计的.a静态库包含到一个app应用中,调试时报下面的错误:
*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '+[NSDictionary dictionaryWithJSONString:error:]: unrecognized selector sent to class 0x235e7ec'
unrecognized selector sent to class 0x235e7ec'
*** First throw call stack:
(
0 CoreFoundation 0x022195e4 __exceptionPreprocess + 180
1 libobjc.A.dylib 0x01f288b6 objc_exception_throw + 44
2 CoreFoundation 0x022b67a3 +[NSObject(NSObject) doesNotRecognizeSelector:] + 275
3 CoreFoundation 0x0220990b ___forwarding___ + 1019
4 CoreFoundation 0x022094ee _CF_forwarding_prep_0 + 14
...
10 Foundation 0x01b80597 -[NSThread main] + 76
11 Foundation 0x01b804f6 __NSThread__main__ + 1275
12 libsystem_c.dylib 0x02d625b7 _pthread_start + 344
13 libsystem_c.dylib 0x02d4cdce thread_start + 34
)
libc++abi.dylib: terminating with uncaught exception of type NSException
纠结了好久,定位代码错误位置如下:
- NSString *retString = [network SendData:url data:requestDictionary];
- NSError *error = nil;
- NSDictionary *retDictionary = [ NSDictionary dictionaryWithJSONString:retString error:&error];
- if(!error)
- {
- ret.flag = [[retDictionary objectForKey:@\"flag\" ] intValue];
- ret.msg = [retDictionary objectForKey:@\"msg\"];
- }
- return ret;
- }
推断原因是:NSDictionary 是内嵌对象,但是dictionaryWithJSONString 另一个自定义对象的方法。为什么要用与NSDictionary 相同的名称,原因就是要返回NSDictionary 对象。
自定义对象代码如下:
- @implementation NSDictionary (NSDictionary_JSONExtensions)
- + (id)dictionaryWithJSONData:(NSData *)inData error:(NSError **)outError
- {
- return([[CJSONDeserializer deserializer] deserialize:inData error:outError]);
- }
- + (id)dictionaryWithJSONString:(NSString *)inJSON error:(NSError **)outError;
- {
- NSData *theData = [inJSON dataUsingEncoding:NSUTF8StringEncoding];
- return([self dictionaryWithJSONData:theData error:outError]);
- }
- @end
所以,推断xcode没有正确解析代码,把dictionaryWithJSONString 方法错误认为是内嵌对象NSDictionary 的内部方法,但NSDictionary 没有这个方法,所以调试的时候,就找不到该方法的实现,报出错误信息:unrecognized selector sent to class 0x235e7ec'
推断出问题的可能原因后,很有可能是工程的setting信息有问题。于是开始一个一个参数过,一开始以为是Search Paths的各种路径配置错误,后来验证不是。否则编译都应该过不去。
于是,将范围定在Build Settings下的Linking的参数列表。马上有一个参数映入眼帘:Other Linker Flags,没有设置。通过google,查询相关说明:
-all_load Loads all members of static archive libraries.
-ObjC Loads all members of static archive libraries that implement an Objective-C class or category.
-force_load (path_to_archive) Loads all members of the specified static archive library. Note: -all_load forces all members of all archives to be loaded. This option allows you to target a specific archive.
翻译过来就是-all_load就是会加载静态库文件中的所有成员,-ObjC就是会加载静态库文件中实现一个类或者分类的所有成员,-force_load(包的路径)就是会加载指定路径的静态库文件中的所有成员。所以对于使用runtime时候的反射调用的方法应该使用这三个中的一个进行link,以保证所有的类都可以加载到内存中供程序动态调用
到这里,基本就明白了,就是这个参数没有设置的原因。将Other Linker Flags=-ObjC,再重新调试,运行成功!!