UITextField and interesting program - iphone

Question

Firstly, sorry for my English... I want to write a program which is going to calculate distances between two cities. For example, in UITextField we write Paris, and in the second UITextField we write the second , "London. And We have a base of longitude s and latitude s of all Cities. Our program has distance formula which uses these four numbers. We know this formula.
When the user insert a name in UITextField i want to TAKE THIS .text AND COMPARE IT WITH OUR BASE. How to do that?? I can do a program like this but it`s ....stupid:
#interface City : UIViewController{
IBOutlet UITextField *city1;
IBOutlet UITextField *city2;
}
#property (nonatomic, retain) IBOutlet UITextField *city1;
#property (nonatomic, retain) IBOutlet UITextField *city2;
-(void) calculate;
#end
#import "City.h"
#implementation City
#synthesize city1, city2;
-(void) viewDidLoad
{
// to check changes in textfields i`m using NSTimer, I know it`s stupid but I haven`t learned how to make it in different way
[NSTimer scheduledTimerWithTimeInterval:1 target:self selector:#selector(calculate) userInfo:nil repeats:YES];
}
-(void) obliczenia
{
double distance;
if([city1 is EqualToString:#"Paris"] && [city2 is EqualToString:#"London"])
{
double Paris_lat = x1;
double Paris_lon = y1;
double London_lat = x2;
double London_lon = y2;
distance =...; // we know the formula for distance but this is not important for now.
// distance shows in some label but this is not a point of my problem.
}
}
It runs but when we have few cities. But when we have thousand cities, writing code would be a nonsens.
I am starting with iPhone programming.
Thank you for patience and please, help me. It s very important but I can't find a solution.

Answer 1

Take a look at this guide:
http://developer.apple.com/library/mac/#documentation/Cocoa/Conceptual/PropertyLists/AboutPropertyLists/AboutPropertyLists.html
Basically, put all of your data into a property list, like so:
<dict>
<key>Paris</key>
<dict>
<key>x</key>
<real>20.2</real>
<key>y</key>
<real>30.4</real>
</dict>
...
</dict>
And then load it like this:
NSDictionary * data = [[NSDictionary alloc] initWithContentsOfFile:[[NSBundle mainBundle] pathForResource:#"NAMEOFPLIST" ofType:#"plist"]];
NSDictionary * paris = [data objectForKey:#"Paris"];
float xparis = [[paris objectForKey:#"x"] floatValue];
float yparis = [[paris objectForKey:#"y"] floatValue];
In your case you'd do something like this:
NSDictionary * data = [[NSDictionary alloc] initWithContentsOfFile:[[NSBundle mainBundle] pathForResource:#"NAMEOFPLIST" ofType:#"plist"]];
NSDictionary * city1Data = [data objectForKey:city1.text];
NSDictionary * city2Data = [data objectForKey:city2.text];
if (city1Data != nil && city2Data != nil) {
// Do what you need...
}
And then do what you need with the data.

Answer 2

You are probably better off using a picker view to display the available cities, or use a live search in your textview to autocomplete, or provide selections for your cities.
If you have a constrained set of inputs (in this case, the names of the cities for which you have long, lat values) it's a better idea to constrain the user's input to these values.

Answer 3

You can create a Array with all Country Names and compare each Country Name in the Array with your input.
NSArray *countries = [NSArray arrayWithObjects:#"Berlin", #"Rom", nil];
for (NSString *c in countries) {
if ([city1 isEqualToString:c]) {
//do something
}
}