ios - NSString Category Method Not Getting Called -

the problem trying solve convert nil strings empty strings can put value in nsdictionary.

i have following code:

//accessed in class   prospect.title = [self.titlelabel.text emptywhennil];  // nsstring+additions category  -(nsstring *) emptywhennil {    if(self == nil)       return @"";     return self;  } 

but reason emptywhennil method never invoked!! lost..

the problem is, when string pointer nil, have no object send category message to. messages nil not executed (and return nil) in objective-c.

if want put "null" objects collection, such nsdictionary, or nsarray, can use nsnull class instead.

alternatively implement method class method:

+ (nsstring *)emptystringifnil:(nsstring *)str {     if (!str) return @"";     return str; } 

you call

prospect.title = [nsstring emptystringifnil:self.titlelabel.text];