处理 object_getIvar(id object, Ivar ivar) 的返回值 [英] Handling the return value of object_getIvar(id object, Ivar ivar)
问题描述
1) object_getIvar(id object, Ivar ivar) 如果 Ivar 是一个对象,则返回一个id",例如.如果变量是 NSString,则大概是包含该值的 id = NSString.那是对的吗?或者我需要做什么才能访问 Ivar 的值.
1) object_getIvar(id object, Ivar ivar) returns an 'id' if the Ivar is an object eg. if the variabe is an NSString, presumably the id = NSString which contains the value. Is that correct? Or what do I need to do to access the value of the Ivar.
2) 如果 Ivar 是一个浮点数/整数等.将返回什么以及如何将其转换为我可以使用的内容(浮点数或整数很好,因为我可以使用 NSNumber numberWithXXX 将其转换为对象).
2) if the Ivar is a float/int etc. what will get returned and how do I convert it into something I can use (a float or int is fine as I can use NSNumber numberWithXXX to convert it to an object).
推荐答案
打印任意对象描述的示例:
Example use for printing the description of arbitrary objects:
- (NSString *) qCustomDescription
{
static int depth = 0;
NSMutableString *resultString = [NSMutableString stringWithFormat: @"<%@: %p>", NSStringFromClass([self class]), self];
uint32_t ivarCount;
Ivar *ivars = class_copyIvarList([self class], &ivarCount);
if( ivars )
{
++depth;
[resultString appendString: @"\n"];
for( int tabs = depth; --tabs > 0; )
[resultString appendString: @"\t"];
[resultString appendString: @"{"];
for( uint32_t i = 0; i < ivarCount; ++i )
{
Ivar ivar = ivars[i];
const char* type = ivar_getTypeEncoding(ivar);
const char* ivarName = ivar_getName( ivar );
NSString* valueDescription = @"";
NSString* name = [NSString stringWithCString: ivarName encoding: NSASCIIStringEncoding];
switch( type[0] )
{
case '@':
{
id v = object_getIvar(self, ivar);
if( v )
{
if( [self respondsToSelector: @selector(qDescriptionForValue:)] )
valueDescription = [self performSelector: @selector(qDescriptionForValue:) withObject: v];
else
valueDescription = [v description];
}
break;
}
case 'c':
{
char v = ((char (*)(id, Ivar))object_getIvar)(self, ivar);
valueDescription = [NSString stringWithFormat: @"%c", v];
break;
}
case 'i':
{
int v = ((int (*)(id, Ivar))object_getIvar)(self, ivar);
valueDescription = [NSString stringWithFormat: @"%i", v];
break;
}
case 's':
{
short v = ((short (*)(id, Ivar))object_getIvar)(self, ivar);
valueDescription = [NSString stringWithFormat: @"%d", v];
break;
}
case 'l':
{
long v = ((long (*)(id, Ivar))object_getIvar)(self, ivar);
valueDescription = [NSString stringWithFormat: @"%ld", v];
break;
}
case 'q':
{
long long v = ((long long (*)(id, Ivar))object_getIvar)(self, ivar);
valueDescription = [NSString stringWithFormat: @"%lld", v];
break;
}
case 'C':
{
unsigned char v = ((unsigned char (*)(id, Ivar))object_getIvar)(self, ivar);
valueDescription = [NSString stringWithFormat: @"%uc", v];
break;
}
case 'I':
{
unsigned int v = ((unsigned int (*)(id, Ivar))object_getIvar)(self, ivar);
valueDescription = [NSString stringWithFormat: @"%u", v];
break;
}
case 'S':
{
unsigned short v = ((unsigned short (*)(id, Ivar))object_getIvar)(self, ivar);
valueDescription = [NSString stringWithFormat: @"%u", v];
break;
}
case 'L':
{
unsigned long v = ((unsigned long (*)(id, Ivar))object_getIvar)(self, ivar);
valueDescription = [NSString stringWithFormat: @"%lu", v];
break;
}
case 'Q':
{
unsigned long long v = ((unsigned long long (*)(id, Ivar))object_getIvar)(self, ivar);
valueDescription = [NSString stringWithFormat: @"%llu", v];
break;
}
case 'f':
{
float v = ((float (*)(id, Ivar))object_getIvar)(self, ivar);
valueDescription = [NSString stringWithFormat: @"%f", v];
break;
}
case 'd':
{
double v = ((double (*)(id, Ivar))object_getIvar)(self, ivar);
valueDescription = [NSString stringWithFormat: @"%f", v];
break;
}
case 'B':
{
BOOL v = ((BOOL (*)(id, Ivar))object_getIvar)(self, ivar);
valueDescription = [NSString stringWithFormat: @"%@", v ? @"YES" : @"NO"];
break;
}
case '*':
{
char *v = ((char* (*)(id, Ivar))object_getIvar)(self, ivar);
valueDescription = [NSString stringWithFormat: @"%s", v];
break;
}
case '#':
{
id v = object_getIvar(self, ivar);
valueDescription = [NSString stringWithFormat: @"Class: %s", object_getClassName(v)];
break;
}
case ':':
{
SEL v = ((SEL (*)(id, Ivar))object_getIvar)(self, ivar);
valueDescription = [NSString stringWithFormat: @"Selector: %s", sel_getName(v)];
break;
}
case '[':
case '{':
case '(':
case 'b':
case '^':
{
valueDescription = [NSString stringWithFormat: @"%s", type];
break;
}
default:
valueDescription = [NSString stringWithFormat: @"UNKNOWN TYPE: %s", type];
break;
}
[resultString appendString: @"\n"];
for( int tabs = depth; --tabs >= 0; )
[resultString appendString: @"\t"];
[resultString appendFormat: @"%@: %@", name, valueDescription];
}
[resultString appendString: @"\n"];
for( int tabs = depth; --tabs > 0; )
[resultString appendString: @"\t"];
[resultString appendString: @"}"];
--depth;
free(ivars);
}
return resultString;
}
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