Question

here is the problem :

NSArray * alphabets = [NSArray arrayWithObjects:@"a",@"b",@"c",@"d",@"e",@"f",@"g",@"h",@"i",@"j",@"k",@"l",@"m",@"n",@"o",@"p",@"q",@"r",@"s",@"t",@"u",@"v",@"w",@"x",@"y",@"z",nil];
NSDictionary * alphaToNum = [NSDictionary dictionaryWithObject:alphabets forKey:1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26];
//I know above line meant to not work I just brought it here as an example

how can I create a dictionary just like above which is working?

Answer 1

You can only use objects as keys or values in a NSDictionary, so you have to use NSNumber as wrapper for your integer key.

NSMutableDictionary *alphaToNum = [NSMutableDictionary dictionary];
NSArray *alphabet = [NSArray arrayWithObjects:@"a",@"b",@"c",@"d",@"e",@"f",@"g",@"h",@"i",@"j",@"k",@"l",@"m",@"n",@"o",@"p",@"q",@"r",@"s",@"t",@"u",@"v",@"w",@"x",@"y",@"z",nil];
NSInteger index = 0;

for(NSString *character in alphabet)
{
    index ++;
    [alphaToNum setObject:character forKey:[NSNumber numberWithInteger:index]];
}