NSString may not respond to append string

Question

I have a NSMutableString and I am trying to use appendString method. Though it works fine but every time I use it, I receive a warning NSString may not respond to append string. This is my code :

-(void)parser:(NSXMLParser *)parser foundCharacters:(NSString *)string{

    [soapResults appendString: string];        //soapResults is an NSMutableString in .h
}

I know I am getting this warning because of NSString string but how to remove this warning?

Vijay-Apple-Dev.blogspot.com · Accepted Answer · 2011-09-06T11:04:12.817

3

self.soapResults=(NSMutableString *)[self.soapResults stringByAppendingString:string];

or

soapResults=(NSMutableString *)[soapResults stringByAppendingString:string];

OR

self.soapResults=(NSMutableString *)[[self.soapResults stringByAppendingString:string] mutableCopy];

    //    or

soapResults=(NSMutableString *)[[soapResults stringByAppendingString:string] mutableCopy];

edited Sep 06 '11 at 11:04

answered Sep 06 '11 at 10:42

Vijay-Apple-Dev.blogspot.com

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stringByAppendingString which will return NSString. so we have to manually specify NSMutableString* – Vijay-Apple-Dev.blogspot.com Sep 06 '11 at 10:49
take a look at this http://stackoverflow.com/questions/5894910/why-does-nsstring-respond-to-appendstring – Vijay-Apple-Dev.blogspot.com Sep 06 '11 at 10:58
@nitish u r welcome.but be responsive to others while they ask or request.thanks again.have a nice day. – Vijay-Apple-Dev.blogspot.com Sep 06 '11 at 11:21
Sorry for my previous comment (that I deleted since): I haven't seen the "mutableCopy" in your code (it was offscreen and had no scrollbar to tell me). Obviously with ```mutableCopy``` your code works (even if it generates useless allocations to do this way -- generating a new NSString, then a mutableCopy of it -- than to modify an existing NSMutableString) – AliSoftware Sep 06 '11 at 13:16
@AliSoftware all of us not genius in Objective c.but trying to do...that's it.so dont say sorry!!!.u rocks – Vijay-Apple-Dev.blogspot.com Sep 06 '11 at 13:18

score 3 · Answer 2 · answered Sep 06 '11 at 10:57

If you are sure soapResults is actually an NSMutableString, and only have a warning, then simply cast it before calling appendString: to it :

[(NSMutableString*)soapResults appendString: string];

If you declared soapResults as an NSMutableString but in fact affected an NSString to it, then you probably don't have a warning, but will have a runtime error on execution.

If soapResults is an NSString (either because you declared it so or because you affected an NSString to it), you may instead create a new NSString by appending string to it, then create a mutableCopy from it... but I don't recommend this as it will generate useless allocations (and NSMutableString is better to avoid this)

Thanks a lot. But as AppleVijay posted the correct answer earlier I must accept his answer :) — Nitish, Sep 06 '11 at 11:19

zaph · Answer 3 · 2011-09-06T11:55:15.913

Simply, at this point in the code soapResults is not a NSMutableString. Perhaps somewhere else in the code it is inadvertently replaced with a NSString.

As an aside, NSString is really an NSMutableString code-wise even though NSMutableString is a subclass of NSString. This might help explain what is happening in the code.

Still, casting an NSString to an NSMutableString is not a good idea, what really needs to be done is find where it is becoming an NSString and fix that.

NSString may not respond to append string

3 Answers3