if statements and stringWithFormat - ios

Question

I need to know if there is a way to use if statements to display certain nsstrings, depending on whether or not that NSString contains any data.
I have an nsstringcalled visitorInfo.
The string uses data from other strings (i.e. which operating system the user is running) and displays that info. Here is an example of what I'm talking about:
NSString *visitorInfo = [NSString stringWithFormat:#"INFO\n\nVisitor Location\n%#\n\nVisitor Blood Type\n\%#", _visitor.location, _visitor.bloodType];
And it would display like this:
INFO
Location
Miami, FL
Blood Type
O positive
However, I have several pieces of data that only load if the user chooses to do so. i.e their email address.
This section of code below would do what I want, but my visitorInfo string contains tons of different strings, and if I use this code below, then it won't load any of them if the user chooses not to submit his blood type.
if ([self.visitor.bloodType length] > 0) {
NSString *visitorInfo = [NSString stringWithFormat:#"INFO\n\nVisitor Location\n%#\n\nVisitor Blood Type\n\%#", _visitor.location, _visitor.bloodType];
}
So basically if their is data stored in bloodType then i went that code to run, but if there isn't any data I only want it to skip over bloodType, and finish displaying the rest of the data.
Let me know if you have any more questions
Additional details. I'm using an NSString for a specific reason, which is why I'm not using a dictionary.

Answer 1

Just build up the string as needed using NSMutableString:
NSMutableString *visitorInfo = [NSMutableString stringWithFormat:#"INFO\n\nVisitor Location\n%#, _visitor.location];
if ([self.visitor.bloodType length] > 0) {
[visitorInfo appendFormat:#"\n\nVisitor Blood Type\n\%#", _visitor.bloodType];
}

Answer 2

You can check if a string has any data in it by using the following
if([_visitor.location length]<1){
//This means there's no data and is a better way of checking, rather than isEqualToString:#"".
}else{
//there is some date here
}
** EDIT - (just re-reading your question, sorry this answer is dependant on _visitor.location being a string in the first place)*
I hope this helps

Answer 3

Try this -
NSString *str = #"INFO";
if (_visitor.location) {
str = [NSString stringWithFormat:#"\n\nVisitor Location\n%#",_visitor.location];
}
if (_visitor.bloodType) {
str = [NSString stringWithFormat:#"\n\nVisitor Blood Type\n\%#",_visitor.bloodType];
}