NSAttributedString, change the font overall BUT keep all other attributes?

Question

Say I have an NSMutableAttributedString .

The string has a varied mix of formatting throughout:

Here is an example:

Answer 1

Obj-C version of @manmal's answer

@implementation NSMutableAttributedString (Additions)

- (void)setFontFaceWithFont:(UIFont *)font color:(UIColor *)color {
    [self beginEditing];
    [self enumerateAttribute:NSFontAttributeName
                     inRange:NSMakeRange(0, self.length)
                     options:0
                  usingBlock:^(id  _Nullable value, NSRange range, BOOL * _Nonnull stop) {
                      UIFont *oldFont = (UIFont *)value;
                      UIFontDescriptor *newFontDescriptor = [[oldFont.fontDescriptor fontDescriptorWithFamily:font.familyName] fontDescriptorWithSymbolicTraits:oldFont.fontDescriptor.symbolicTraits];
                      UIFont *newFont = [UIFont fontWithDescriptor:newFontDescriptor size:font.pointSize];
                      if (newFont) {
                          [self removeAttribute:NSFontAttributeName range:range];
                          [self addAttribute:NSFontAttributeName value:newFont range:range];
                      }

                      if (color) {
                          [self removeAttribute:NSForegroundColorAttributeName range:range];
                          [self addAttribute:NSForegroundColorAttributeName value:newFont range:range];
                      }
                  }];
    [self endEditing];
}

@end