Convert NSString into NSMutableArray

Question

I am trying to convert (or copy?) a NSString into a NSMutableArray. I guess my problem is that I don't really understand the structure of a MutableArray. In my limited knowledge, an Array could look like this:

NoteBook = [[NSMutableArray alloc] init];

for (int temp = 0; temp < 3; temp++) {
    [NoteBook insertObject:@"Page" atIndex:temp];
}

Which would give me an Array of PagePagePage. Let's assume I wanted to open a txt file which contains PagePagePage, but the words were separated by a defined string so that I can keep the individual objects in my array apart, like so: Page--- end of page ---Page--- end of page ---Page.

Now, my next step would be to read this information from the txt file:

NSString *tempTextOut = [NSString stringWithContentsOfFile:filePath
                                                 encoding:NSUTF8StringEncoding
                                                    error:&error];
NoteBook = [tempTextOut componentsSeparatedByString: @"\n--- end of page ---\n"];

However, the last line does not work and I'm told by xCode: Incompatible Objective-C types assigning 'struct NSArray*', expected 'struct NSMutableArray*'. I don't really understand this - NSArray and MutableArray should be compatible (as one is the subclass of the other). Shouldn't xCode tell me that the problem is that I've been trying to convert a NSString into an NSMutableArray?

Would I perhaps need to re-set my MutableArray before putting something back into it, because right now, it still contains PagePagePage which I have assigned to it in the first step. I thought my NoteBook mutable array would simply be replaced by the string, but I guess that won't be the case.

I'd very much appreciate any help in this matter. Thanks!

Convert NSString separated by comma to NSArray

beryllium
– beryllium

2012-03-26 19:55:25 +00:00
Commented Mar 26, 2012 at 19:55 — beryllium
– beryllium, Commented Mar 26, 2012 at 19:55

Anomie · Accepted Answer · 2011-03-23 12:41:06Z

4

componentsSeparatedByString: returns a plain immutable NSArray, not an NSMutableArray. You can pass the array to [NSMutableArray arrayWithArray:] or use mutableCopy on the array to get a mutable array from it, or you can use addObjectsFromArray: on an existing NSMutableArray to add objects to it.

If you go the mutableCopy route, do remember that you are responsible for calling release or autorelease on it.

answered Mar 23, 2011 at 12:41

Anomie

95.5k13 gold badges130 silver badges145 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Nick Weaver · Accepted Answer · 2011-03-23 12:52:22Z

3

Assigning a mutable object to the same immutable type will lead to runtime errors if you want to manipulate the immutable instance.

You can get your mutable copy by calling:

NoteBook = [[tempTextOut componentsSeparatedByString: @"\n--- end of page ---\n"] mutableCopy];

If NoteBook is a retained property you should assign to it this way:

self.NoteBook = [[[tempTextOut componentsSeparatedByString: @"\n--- end of page ---\n"] mutableCopy] autorelease];

so the mutable copy doesn't get over retained. You can release in your dealloc method then as normal.

edited Mar 23, 2011 at 12:52

answered Mar 23, 2011 at 12:40

Nick Weaver

47.3k12 gold badges100 silver badges108 bronze badges

4 Comments

Noah Witherspoon Over a year ago

Note that you're then responsible for releasing NoteBook eventually, as it's not going to be autoreleased like the original array.

Nick Weaver Over a year ago

Yes, you claim ownership by calling mutableCopy.

n.evermind Over a year ago

@Noah Witherspoon: Thanks! I've already have it released in my dealloc method at the very end of the program, but it was there before as I did the alloc init thing at the very beginning for NoteBook. Are you therefore saying that I need to release it somewhere else as well? Or will it suffice to release it in my dealloc? I guess you didn't mean the tempTextOut as this will be autoreleased, right?

n.evermind Over a year ago

Thanks, that explains it beautifully! I think this is the first time I understood what getting over retained means. Thanks so much for this illuminating moment!

Collectives™ on Stack Overflow

Convert NSString into NSMutableArray

2 Answers 2

Comments

4 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

4 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related