Question

I just can’t seem to resolve the error that comes up here: “Assigning to ‘NSMutableString *__strong’ from incompatible type ‘void'”. The array string value I am trying to append is an NSArray constant.

NSMutableString *reportString     
reportString = [reportString appendString:[reportFieldNames objectAtIndex:index]];

Answer 1

appendString is a void method; you are probably looking for

reportString = [NSMutableString string];
[reportString appendString:[reportFieldNames objectAtIndex:index]];

You can avoid append altogether by combining it with the initialization:

reportString = [NSMutableString stringWithString:[reportFieldNames objectAtIndex:index]];

Note that there is another appending method of NSString that requires an assignment:

NSString *str = @"Hello";
str = [str stringByAppendingString:@", world!"];