Question

I’ve managed NSUserDefaults and stuck with writing the method to filter the SQL select according to settings in standardUserDefaults.

My app shows 6 continents and user has an option to disable some of them. In my SQL methods I currently trying to manage it this way:

if (![[NSUserDefaults standardUserDefaults] boolForKey:@"europe"])
    {
        sqlContinents="SELECT cont.continentID,cont.continentName,cont.continentImage\
        FROM Continents as cont\
        WHERE cont.continentID <> 1";           
    }

It will work if user will disable only europe, but what if he will disable more continents… so I can’t figure out how write code that will check which continents are disabled and omit them.

Of cause there’s an option to write many “ifs” like
if(![[NSUserDefaults standardUserDefaults] boolForKey:@”europe”] && ….&&……), but I would be very thankful if someone will show me how to implement such method in more smart and elegant way. Thank you in advance.

Answer 1

You can create a WHERE string that holds all conditions before the SQL sentence.

NSString where = @"WHERE";

if (![[NSUserDefaults standardUserDefaults] boolForKey:@"europe"]){
   where = [where stringByAppendingString: @" cont.continentID <> 1 "];
}

// Rest of continents...

sqlContinents = [@"SELECT cont.continentID,cont.continentName,cont.continentImage\
        FROM Continents as cont " stringByAppendingString: where];