打印伊娃值的通用Objective-C描述方法

Question

在Objective-C中，通常用打印对象ID和实例变量名称/值的方法覆盖-description。我想制作一个通用的-description方法，通过内省来完成此操作，而不是手动为每个类执行此操作。我想输出是这样的：

<ClassName: 0x??????, ivar1: value1, ivar2: value2, ivar3: value3, ...> 

这也将是不错的实例变量名称排序（所以他们总是以相同的顺序）。最后，如果这可以安全地覆盖NSObject功能，那将是完美的（但我认为这并不简单，因为NSObject.m在-description中有关于使用-[NSString stringWithFormat:]的警告）。

Answer 1

这是一个很好的问题！因为我还没有找到这样的东西，所以我写了一个小功能为你做这个。它会用NSObject的NSObject替换NSObject使用方法swizzling（是的，我是这个邪恶的MAHAHAHAHAHahahahaha），并按他们也出现在课堂上的顺序打印伊娃（你可以轻松编辑它们以按字母顺序显示）。

不要！忘记拨打NSObjectSwizzleDescription()！

.h文件中：

@interface NSObject (JSObjectAdditions) 
@end 


void NSObjectSwizzleDescription(); 

.m文件：

#import <objc/objc.h> 
#import "JSObject.h" 

@implementation NSObject (JSObjectAdditions) 

- (NSString *)verboseDescription 
{ 
    NSMutableString *description = [NSMutableString stringWithFormat:@"<%@: %p>", NSStringFromClass([self class]), self]; 

    uint32_t ivarCount; 
    Ivar *ivars = class_copyIvarList([self class], &ivarCount); 

    if(ivars) 
    { 
     [description appendString:@"\n{"]; 

     for(uint32_t i=0; i<ivarCount; i++) 
     { 
      Ivar ivar = ivars[i]; 
      const char *ivarType = ivar_getTypeEncoding(ivar); 
      id ivarObject = object_getIvar(self, ivar); 

      [description appendFormat:@"\n %s: ", ivar_getName(ivar)]; 

      // Default signed data types 
      if(strcmp(ivarType, "c") == 0) 
      { 
       char character = (char)ivarObject; 
       [description appendFormat:@"'%c'", character]; 
      } 
      else if(strcmp(ivarType, "i") == 0 || strcmp(ivarType, "l") == 0) // l is also 32 bit in the 64 bit runtime environment 
      { 
       int integer = (int)ivarObject; 
       [description appendFormat:@"%i", integer]; 
      } 
      else if(strcmp(ivarType, "s") == 0) 
      { 
       short shortVal = (short)ivarObject; 
       [description appendFormat:@"%i", (int)shortVal]; 
      } 
      else if(strcmp(ivarType, "q") == 0) 
      { 
       long long longVal = (long long)ivarObject; 
       [description appendFormat:@"%l", longVal]; 
      } 
      // Default unsigned data types 
      else if(strcmp(ivarType, "C") == 0) 
      { 
       unsigned char chracter = (unsigned char)ivarObject; 
       [description appendFormat:@"'%c'", chracter]; 
      } 
      else if(strcmp(ivarType, "I") == 0 || strcmp(ivarType, "L") == 0) 
      { 
       unsigned int integer = (unsigned int)ivarObject; 
       [description appendFormat:@"%u", integer]; 
      } 
      else if(strcmp(ivarType, "S") == 0) 
      { 
       unsigned short shortVal = (unsigned short)ivarObject; 
       [description appendFormat:@"%i", (int)shortVal]; 
      } 
      else if(strcmp(ivarType, "Q") == 0) 
      { 
       unsigned long long longVal = (unsigned long long)ivarObject; 
       [description appendFormat:@"%ll", longVal]; 
      } 
      // Floats'n'stuff 
      else if(strcmp(ivarType, "f") == 0) 
      { 
       float floatVal; 
       memcpy(&floatVal, &ivarObject, sizeof(float)); 

       [description appendFormat:@"%f", floatVal]; 
      } 
      else if(strcmp(ivarType, "d") == 0) 
      { 
       double doubleVal; 
       memcpy(&doubleVal, &ivarObject, sizeof(double)); 

       [description appendFormat:@"%f", doubleVal]; 
      } 
      // Boolean and pointer 
      else if(strcmp(ivarType, "B") == 0) 
      { 
       BOOL booleanVal = (BOOL)ivarObject; 
       [description appendFormat:@"%@", (booleanVal ? @"YES" : @"NO")]; 
      } 
      else if(strcmp(ivarType, "v") == 0) 
      { 
       void *pointer = (void *)ivarObject; 
       [description appendFormat:@"%p", pointer]; 
      } 
      else if(strcmp(ivarType, "*") == 0 || strcmp(ivarType, ":") == 0) // SEL is just a typecast for a cstring 
      { 
       char *cstring = (char *)ivarObject; 
       [description appendFormat:@"\"%s\"", cstring]; 
      } 
      else if(strncmp(ivarType, "@", 1) == 0) 
      { 
       [description appendFormat:@"%@", ivarObject]; 
      } 
      else if(strcmp(ivarType, "#") == 0) 
      { 
       Class objcClass = (Class)ivarObject; 
       [description appendFormat:@"%s", class_getName(objcClass)]; 
      } 
      else 
       [description appendString:@"???"]; 
     } 

     [description appendString:@"\n}"]; 
     free(ivars); 
    } 

    return description; 
} 

@end 


void NSObjectSwizzleDescription() 
{ 
    Method origMethod = class_getInstanceMethod([NSObject class], @selector(description)); 
    Method newMethod = class_getInstanceMethod([NSObject class], @selector(verboseDescription)); 

    method_exchangeImplementations(origMethod, newMethod); 
} 

Answer 2

我不知道这样做的任何代码，但如果存在，我会对调试目的感兴趣！

我很惊讶我还没有找到像这样的东西，classic techniques只是工作，但它确实很高兴有某种inspect方法，这是我认为，可能使用反射，但也许我'米错了。

我建议看看a this interesting post，这与您正在寻找的内容有关，并且可能是实施它的基础。

另一个有趣的事情是NSLogger，这是一个很好的调试工具。