Objective-C: Relating NSStrings to each other? - ios

Question

I am very new to code in general and I'm in the process of learning Objective-C, so I apologize in advance if I phrased this question incorrectly.
I have created several arrays with this goal in mind:
Show how many people there are and tell their names
Show how many cities there are and tell their names
Assign people to cities and calculate the populations
I have completed that task, but I have assigned each person individually to the array for each city. Is there a way that I can simply relate the NSStrings? For example "blockCity = bill, bob, jim" instead of creating a new array for populations?
// My people
NSString *bill = (#"Bill");
NSString *bob = (#"Bob");
NSString *jim = (#"Jim");
NSString *kevin = (#"kevin");
NSString *stacy = (#"stacy");
NSString *cooper = (#"Cooper");
NSMutableArray *people = [NSMutableArray arrayWithObjects: bill, bob, jim, kevin, stacy, cooper, nil];
NSLog(#"Here are my people: %#", people);
NSLog(#"I have %lu people", [people count]);
// My places
NSString *blockCity = (#"BlockCity");
NSString *hyperCity = (#"HyperCity");
NSString *pixelTown = (#"PixelTown");
NSString *nowhere = (#"Nowhere");
NSMutableArray *cities = [NSMutableArray arrayWithObjects: blockCity, hyperCity, pixelTown, nowhere, nil];
NSLog(#"Cities: %#", cities);
NSLog(#"There are %lu cities", [cities count]);
//populations
// BlockCity population
NSMutableArray *bcpop = [NSMutableArray arrayWithObjects: bill, bob, jim, nil];
if ([bcpop count] == 0) {
NSLog(#"%# is abandoned.", blockCity);
} else {
NSLog(#"%# has a population of %lu", blockCity, [bcpop count]);
}
//HyperCity population
NSMutableArray *hcpop = [NSMutableArray arrayWithObjects: nil];
if ([hcpop count] == 0) {
NSLog(#"%# is abandoned.", hyperCity);
} else {
NSLog(#"%# has a population of %lu", hyperCity, [hcpop count]);
}
//PixelTown population
NSMutableArray *ptpop = [NSMutableArray arrayWithObjects: kevin, stacy, cooper, nil];
if ([ptpop count] == 0) {
NSLog(#"%# is abandoned.", pixelTown);
} else {
NSLog(#"%# has a population of %lu", pixelTown, [ptpop count]);
}
//Nowhere population
NSMutableArray *npop = [NSMutableArray arrayWithObjects: nil];
if ([npop count] == 0) {
NSLog(#"%# is abandoned.", nowhere);
} else {
NSLog(#"%# has a population of %lu", nowhere, [npop count]);
}

Answer 1

No, there is no built-in way you can just “relate the NSStrings”.1
The appropriate thing to do here is to start thinking about your design in an object-oriented way.
What are the different sorts of objects in your program? There are people, so a Person class is appropriate. Give the Person class a name property (an NSString).
There are cities, so a City class is appropriate. Give the City class a name property (an NSString), an inhabitants property (an NSArray or NSMutableArray to be filled with references to Person objects), and a population method (returning unsigned long) that returns the number of inhabitants.
Once you have all that, you can even give City a populationDescription method that returns the string description of its population, like this:
- (NSString *)populationDescription {
if (self.population == 0) {
return [NSString stringWithFormat:#"%# is abandoned.", self.name];
} else {
return [NSString stringWithFormat:#"%# has a population of %lu", self.name, self.population);
}
}
Footnote 1. For the pedants: associated objects don't count. They are not appropriate for this and they are too advanced for a learner at this level.

Answer 2

I will recommend to use NSMutableDictionary in this case to relate people with their city. Something like:
NSMutableArray *people = [NSMutableArray arrayWithObjects: bill, bob, jim, kevin, stacy, cooper, nil];
NSMutableDictionary *cityWithPeople = [[NSMutableDictionary alloc] init];
[cityWithPeople setObject:people forKey:#"CityName"]; // to add people related to that city
NSArray peopleInCity=[cityWithPeople objectForKey:key]; // return array of people in city
Also read here to know how to use NSDictionary