如何在运行时检查iOS4中是否存在字体

// List all fonts on iPhone
NSArray *familyNames = [[NSArray alloc] initWithArray:[UIFont familyNames]];
NSArray *fontNames;
NSInteger indFamily, indFont;
for (indFamily=0; indFamily<[familyNames count]; ++indFamily)
{
  NSLog(@\"Family name: %@\", [familyNames objectAtIndex:indFamily]);
  fontNames = [[NSArray alloc] initWithArray:
      [UIFont fontNamesForFamilyName:
      [familyNames objectAtIndex:indFamily]]];
  for (indFont=0; indFont<[fontNames count]; ++indFont)
  {
      NSLog(@\"    Font name: %@\", [fontNames objectAtIndex:indFont]);
  }
  [fontNames release];
}
[familyNames release];

UIFont

+ (UIFont *)fontWithName:(NSString *)fontName size:(CGFloat)fontSize