Looping Through NSAttributedString Attributes to Increase Font SIze
All I need is to loop through all attributes of NSAttributedString
and increase their font size. So far I got to the point where I successfully loop through and manipulate attributes but I cannot save back to NSAttributedString
. The line I commented out is not working for me. How to save back?
NSAttributedString *attrString = self.richTextEditor.attributedText;
[attrString enumerateAttributesInRange: NSMakeRange(0, attrString.string.length)
options:NSAttributedStringEnumerationReverse usingBlock:
^(NSDictionary *attributes, NSRange range, BOOL *stop) {
NSMutableDictionary *mutableAttributes = [NSMutableDictionary dictionaryWithDictionary:attributes];
UIFont *font = [mutableAttributes objectForKey:NSFontAttributeName];
UIFont *newFont = [UIFont fontWithName:font.fontName size:font.pointSize*2];
[mutableAttributes setObject:newFont forKey:NSFontAttributeName];
//Error: [self.richTextEditor.attributedText setAttributes:mutableAttributes range:range];
//no interfacce for setAttributes:range:
}];
Something like this should work:
NSMutableAttributedString *res = [self.richTextEditor.attributedText mutableCopy];
[res beginEditing];
__block BOOL found = NO;
[res enumerateAttribute:NSFontAttributeName inRange:NSMakeRange(0, res.length) options:0 usingBlock:^(id value, NSRange range, BOOL *stop) {
if (value) {
UIFont *oldFont = (UIFont *)value;
UIFont *newFont = [oldFont fontWithSize:oldFont.pointSize * 2];
[res removeAttribute:NSFontAttributeName range:range];
[res addAttribute:NSFontAttributeName value:newFont range:range];
found = YES;
}
}];
if (!found) {
// No font was found - do something else?
}
[res endEditing];
self.richTextEditor.attributedText = res;
At this point res
has a new attributed string with all fonts being twice their original size.
Create an NSMutableAttributedString
from your original attributed string before you start. On each iteration of the loop, call addAttribute:value:range:
on the mutable attributed string (this will replace the old attributes in that range).
Here is a Swift port of maddy's answer (which works really well for me!). It's wrapped in a little extension.
import UIKit
extension NSAttributedString {
func changeFontSize(factor: CGFloat) -> NSAttributedString {
guard let output = self.mutableCopy() as? NSMutableAttributedString else {
return self
}
output.beginEditing()
output.enumerateAttribute(NSAttributedString.Key.font,
in: NSRange(location: 0, length: self.length),
options: []) { (value, range, stop) -> Void in
guard let oldFont = value as? UIFont else {
return
}
let newFont = oldFont.withSize(oldFont.pointSize * factor)
output.removeAttribute(NSAttributedString.Key.font, range: range)
output.addAttribute(NSAttributedString.Key.font, value: newFont, range: range)
}
output.endEditing()
return output
}
}