在Objective-C中,通过打印对象ID和实例变量名称/值的方法来覆盖-description是很常见的.我想制作一个通用的描述方法,通过内省来做,而不是为每个类手动这样做.我希望输出如下：
<ClassName: 0x??????,ivar1: value1,ivar2: value2,ivar3: value3,...>
对实例变量名进行排序也是很好的(所以它们总是按照相同的顺序排列).最后,如果这可以安全地覆盖NSObject功能,那将是完美的(但是我看到这并不简单,因为NSObject.m有一个关于在-description中使用 – [NSString stringWithFormat：]的警告).
解决方法
这是一个很好的问题！因为我没有找到这样的东西,我写了一个小功能,为你做这个.它使用方法swizzling替换(NSString *)NSObject的描述(是的,我是这个邪恶的MAHAHAHAHAHAHAHAHAHAHAHAHAHA),并按照它们也出现在类中的顺序打印出ivar(您可以轻松地编辑它们以字母顺序显示) .
别！忘了调用NSObjectSwizzleDescription()！
.h文件：
@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","S") == 0)
{
unsigned short shortVal = (unsigned short)ivarObject;
[description appendFormat:@"%i","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,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);
}
