1) object_getIvar(id object, Ivar ivar) は、Ivar がオブジェクトの場合、「id」を返します。変数が NSString の場合、おそらく値を含む id = NSString です。あれは正しいですか？または、Ivar の値にアクセスするにはどうすればよいでしょうか。
2) Ivar が float/int などの場合、返されるものと、それを使用できるものに変換する方法 (NSNumber numberWithXXX を使用してオブジェクトに変換できるため、float または int で問題ありません)。
1) 正しい。ドキュメントで述べたように：
戻り値
ivar で指定されたインスタンス変数の値、または object が nil の場合は nil。
2) Ivar の型に関係なく、常に Ivar が保持する値を取得します。ivar_getTypeEncodingを使用して、Ivar のタイプを判別できます。さまざまなタイプのエンコーディングのリストがここにあります。
その情報が手元にあれば、それぞれのケースを適切に処理するスイッチを作成できるはずです。例えば：
(警告: テストされていないコードが先にあります)
const char* typeEncoding = ivar_getTypeEncoding(var);
switch (typeEncoding) {
case '@': {
// handle class case
} break;
case 'i': {
// handle int case
} break;
case 'f': {
// handle float case
} break;
// .. and so on
}
任意のオブジェクトの説明を印刷するための使用例:
- (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;
}