A mutable string object that also contains attributes (such as visual style, hyperlinks, or accessibility data) associated with various portions of its text content.
The NSMutableAttributedString class declares additional methods for mutating the content of an attributed string. You can add and remove characters (raw strings) and attributes separately or together as attributed strings. See the class description for NSAttributedString for more information about attributed strings.
NSMutableAttributedString adds two primitive methods to those of NSAttributedString. These primitive methods provide the basis for all the other methods in its class. The primitive replaceCharactersInRange:withString: method replaces a range of characters with those from a string, leaving all attribute information outside that range intact. The primitive setAttributes:range: method sets attributes and values for a given range of characters, replacing any previous attributes and values for that range.
Note that the default font for NSAttributedString objects is Helvetica 12-point, which may differ from the macOS system font, so you may wish to create the string with non-default attributes suitable for your application using, for example, initWithString:attributes:.
Overridden by subclasses to buffer or optimize a series of changes to the receiver’s characters or attributes, until it receives a matching endEditing message, upon which it can consolidate changes and notify any observers that it has changed.