Best way to initialise / clear a string variable cocoa

问题

I have a routine that parses text via a loop. At the end of each record I need to clear my string variables but I read that someString = @"" actually just points to a new string & causes a memory leak.

What is the best way to handle this? Should I rather use mutable string vars and use setString:@"" between iterations?

回答1:

You have to be careful in which case you create the NSString: (factory method) or (alloc init or (using @"").

If you use @"", it is a constant string, see here: Constant NSString

If you use [[NSString alloc] init], you need to release it.You just need to do [someString release].

If you use something like [NSString stringWithFormat:@""], you don't need to release it because it is already auto released by runtime

回答2:

Since NSStrings are immutable, you cannot change the contents of the string. And by initializing it with @"" you're actually creating a constant NSString object.

You can either work with a NSString local to the loop, and release it in the end of the loop - or you can use a NSMutableString instead. I would prefer the loop local string though.

for ( ; ;) {
    NSString* str = [[NSString alloc] initWithFormat:@"%@", CONTENT];
    ...
    [str release];
}

来源：https://stackoverflow.com/questions/2922196/best-way-to-initialise-clear-a-string-variable-cocoa