Comparing strings in objective c

Question

NSString *title = [myWebView 
                   stringByEvaluatingJavaScriptFromString:@"document.title"];
NSMutableArray *array = [[NSMutableArray alloc] initWithCapacity:8];  
int j = 0;
int i=0;
int count=0;   
int len;
len = [title length];

for(i=0;i<len;i++){
    NSString *c = [title substringWithRange:NSMakeRange(i, 1)];

    if([c isEqualToString:@","])
    {
        //array[count]= [title substringWithRange:NSMakeRange(j, 2)];
        NSString *xxx = [title substringWithRange:NSMakeRange(j,(i-j))];
        NSLog(xxx);

        //insert the string into array
        [array insertObject:xxx atIndex:count];
        j=i;
        count = count + 1;
    }

}

My app always crashes at the line

[c isEqualToString:@","]

and gives the error - Thread1 : Program received signal: "SIGBART".

I know for sure that the problem is occurring while comparing strings since the app runs if I remove that one line of code.

Can someone please help? Thanks

The only way for the app to crash on the isEqualToString line is that the c variable was somehow released. Is your sample code unedited ? Maybe you could try to enable zombie debugging for your application : cocoaforbreakfast.wordpress.com/2011/02/25/… — Emmanuel Sys
– Emmanuel Sys, Commented Nov 13, 2011 at 11:14
Also, if your NSRange is invalid, you can get a NSRangeException. Are you sure there is none? — Emmanuel Sys
– Emmanuel Sys, Commented Nov 13, 2011 at 11:17

zaph · Accepted Answer · 2011-11-13 12:27:44Z

1

Consider using:

- (NSArray *)componentsSeparatedByString:(NSString *)separator

Example:

NSString *title = [myWebView stringByEvaluatingJavaScriptFromString:@"document.title"];
NSMutableArray *array = [title componentsSeparatedByString:@","];

answered Nov 13, 2011 at 12:27

zaph

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7 Comments

Ashish Agarwal Over a year ago

It crashes at the line you mentioned. It printed this line before crashing - [Switching to process 2307 thread 0x207] Current language: auto; currently objective-c

Ashish Agarwal Over a year ago

I also tried running the NSZombie and didn't discover anything out there :(

zaph Over a year ago

Perhaps title is not a valid string.

Ashish Agarwal Over a year ago

NSLog(title) prints out the following line - "part1","part2",number,"11/11/2011","part3","4567.21",4423322

Jakob Egger Over a year ago

I think CocoaFu is on the right track. Maybe the webview returns some strange subclass of NSString that causes the problem. Try NSLog("Class: %@",[title class]);. Maybe you can circumvent the problem using something like title = [NSString stringWithFormat:@"%@", title]. Or just use -isEqual: rather than isEqualToString:

|

justin · Accepted Answer · 2011-11-13 14:24:19Z

0

If I ends up longer than the string, or is undefined, you've got issues. If you replace i with 1, it doesn't crash, right?

Incidentally, you could use:

unichar c = [title characterAtIndex:i];

edited Nov 13, 2011 at 14:24

justin

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answered Nov 13, 2011 at 11:16

Duncan Babbage

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5 Comments

Ashish Agarwal Over a year ago

It still crashed at the same line

Jakob Egger Over a year ago

if c were NULL, (or rather nil since it is an Obj-C object), then the expression would immediately evaluate to 0. In Objective C it is allowed to send messages to nil.

Duncan Babbage Over a year ago

NSLog(@"%@", c); just before the crash line and tell us the output?

Duncan Babbage Over a year ago

Good points, reckless me. Answer edited to focus on the point I was trying to make (still apparently incorrectly).

Ashish Agarwal Over a year ago

It printed all the characters of NSString *title (one in each line)

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