Re: NSMutableString -initWithFormat appends to existing text

[David Chisnall]

On 18 Apr 2018, at 10:23, Mick Bert <micbert75@gmail.com> wrote:
> 
> One question more. I am writing in a text file, by formatting NSString
> objects to give to NSFileHandle -writeData.

That’s a sensible thing to do.  The reason for going via NSData is that 
NSString itself is representation agnostic.  When you generate an NSData, you 
are explicitly telling the string how to encode the characters and transforming 
it into a concrete representation (which may or may not be the same encoding as 
the in-memory representation used by the NSString class).

> Is it the preferable way?

That depends a bit on what you mean by ‘preferable’.  If you mean ‘simpler’ or 
‘cleaner code’, then I don’t think so.  If you mean ‘faster’ or ‘lower memory’, 
then you may find that using NSString’s -getBytes:… method (I forget exactly 
which one GNUstep provides - I need to add the version Apple now provides) into 
an on-stack buffer then write that using the lower-level C / C++ APIs.  In most 
cases, the overhead of the I/O is going to be sufficient that this won’t make a 
noticeable difference, but if you’re processing a lot of data and have NVMe 
storage then you might consider this.

> Are there any other class to work with
> text-oriended files?

Note that text-oriented files don’t really exist as an abstraction on most *NIX 
systems (though the C standard still likes to pretend that they do).  GNUstep / 
Cocoa don’t provide useful abstractions for this, though the C++ standard 
streams library does (not very good ones though, so I don’t really suggest 
using it).

David