xcode 调用类别方法时发送到实例的无法识别的选择器
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Unrecognized selector sent to instance when calling category method
提问by Radu
I have a static library that i made for encryption an XML serialization with i use in my projects. This code worked perfectly until now. but when i included it in my latest project i got an error, i know this error usually appears when the object i call is not properly allocated witch is not the case here the NSLog returns the NSData for my encryption.
我有一个静态库，用于加密我在项目中使用的 XML 序列化。这段代码直到现在都运行良好。但是当我将它包含在我的最新项目中时，我遇到了一个错误，我知道当我调用的对象没有正确分配时，通常会出现这个错误，但在这种情况下，NSLog 返回 NSData 进行加密。
What could be the problem?
可能是什么问题呢？
The error i get is
我得到的错误是
-[NSConcreteData base64EncodingWithLineLength:]: unrecognized selector sent to instance 0x1c9150
*Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSConcreteData base64EncodingWithLineLength:]: unrecognized selector sent to instance 0x1c9150'
-[NSConcreteData base64EncodingWithLineLength:]: 无法识别的选择器发送到实例 0x1c9150
*由于未捕获的异常“NSInvalidArgumentException”而终止应用程序，原因：“-[NSConcreteData base64EncodingWithLineLength:]：无法识别的选择器发送到实例 0x1c9150”
Here is my code:
这是我的代码：
NSData * encryptedMsg =[crypto encrypt:MsgEnc key:[accessdata->Certificate dataUsingEncoding:NSUTF8StringEncoding] padding:&padding];
NSLog(@"encryptedMsg %@",encryptedMsg);
NSString * msg = [NSString stringWithFormat:@"%@", [encryptedMsg base64EncodingWithLineLength:0]];
回答by sergio
As far as I know, base64EncodingWithLineLengthis a method that is not defined in NSDatabut in a category called NSData+Base64.h. The reason why you get the error is that you did not add that category to your project, so that the method is called, it is not found.
据我所知，base64EncodingWithLineLength是一种没有定义的方法，NSData而是在一个名为NSData+Base64.h. 报错的原因是你没有把那个category添加到你的项目中，所以调用了这个方法，没有找到。
So you should add "NSData+Base64.*" files to your project. Get them from here.
所以你应该将“NSData+Base64.*”文件添加到你的项目中。从这里拿走它们。
EDIT:
编辑：
Since the OP mention that the category is included in a static library and assuming the static library is correctly linked, then a possible fix for this issue is adding the
由于 OP 提到该类别包含在静态库中并假设静态库已正确链接，因此此问题的可能解决方法是添加
-ObjC
flag to the "Other linker flags" in your Build Settings. This flag will force the loading of all symbols in Objective C categories, preventing them from being optimized out through the linker.
标记到您的构建设置中的“其他链接器标志”。此标志将强制加载目标 C 类别中的所有符号，防止它们通过链接器进行优化。
回答by ZhangChn
I'm afraid base64EncodingWithLineLength:is a Category method attached onto NSData. That means you should compile/link against the code that implements base64EncodingWithLineLengthfor NSDatacategory.
恐怕base64EncodingWithLineLength:是一个 Category 方法附加到NSData. 这意味着你应该编译/链接对代码实现base64EncodingWithLineLength的NSData类别。
回答by Leszek Zarna
It can help if category refers to Core Data entity: set class for the entity in the managed object model.
如果类别是指核心数据实体，则它会有所帮助：为托管对象模型中的实体设置类。
