Question

I am doing something like this:

NSUserDefaults *standardUserDefaults = [NSUserDefaults standardUserDefaults];

NSString *var1 = [standardUserDefaults objectForKey:@"obj1"];
NSString *var2 = [standardUserDefaults objectForKey:@"obj2"]; 

EmailUtil *email_obj = [[EmailUtil alloc] initWithSubject:@"Some subject" body:[[[@"This is var1: " stringByAppendingString: var1] stringByAppendingString:@" and var2: "] stringByAppendingString: var2]]; 

[email_obj send]; 

Where EmailUtil is just my own utility class which sends the email. This code works fine when the strings var1 and var2 are not nil; however, if they are nil the program will crash. What would be an elegant solution or good practice to follow to ensure the email is sent without a problem, regardless of what the values are?

Thanks!

Answer 1

Before your EmailUtil line, just add:

if(var1==nil) var1 = @"";
if(var2==nil) var2 = @"";

That should solve the crash at least.

Another and probably better way to do it would be to use NSString’s stringWithFormat.
Instead of:

[[[@"This is var1: " stringByAppendingString: var1] stringByAppendingString:@" and var2: "] stringByAppendingString: var2]

Do:

[NSString stringWithFormat:@"This is var1: %@ and var2: %@", var1,var2];

I believe it will say (null) for the nil parameters (didn’t test this). This is probably cleaner than what I had, and your original code too.

Reference: String Format