Issue adding strings to a NSMutableArray using addObject

Question

I've searched other questions and can't seem to find a similar problem. Either I am something completely wrong or I am blind. But here goes the code:

@autoreleasepool {

    NSMutableString *sense = [[NSMutableString alloc] init];
    NSMutableArray *senses = [[NSMutableArray alloc] init];

....... other code which initializes rL and count/length .......

    for (index=0;index<count;index++) {
        for (j=0;j<length;j++) {
            c = [rL characterAtIndex:j];
            switch (c) {
                case '.':
                    [senses addObject:sense];
                    [sense setString:@""];
                    break;
                default:
                    [sense appendFormat:@"%c",c];
                    break;
            }
        }
    }
}

When I do this, and iterate, in debug mode, I see that all objects in senses are same as whatever the last value of sense was.

what am I doing wrong?

gnasher729 · Accepted Answer · 2014-01-30 23:56:34Z

1

"sense" is always the same object. It is a mutable string, so the contents can change, but it is always the same object. So senses will contain that single object, multiple times. You could instead use

[senses addObject:[sense copy]];

answered Jan 30, 2014 at 23:56

gnasher729

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1 Comment

Funky Blue Over a year ago

I thought that was something I was missing. Thanks, that's exactly what I wanted.

rmaddy · Accepted Answer · 2014-01-30 23:53:41Z

1

The immediate solution could be to change:

[senses addObject:sense];

to:

[senses addObject:[NSString stringWithString:sense]];

This will add unique instances instead of adding the same mutable string over and over.

But it appears you are splitting a string up using the "." characters as a delimiter.

There's an easier way:

NSArray *senses = [rl componentsSeparatedByString:@"."];

That's it - one line.

answered Jan 30, 2014 at 23:53

rmaddy

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