Convert positive integer into Roman numerals

NSNumber+conversion.m

#import "NSNumber+conversion.h"

@implementation NSNumber (conversion)

- (NSString*)romanNumerals
{
    assert(self.integerValue > 0);

    static NSString* characterKey = @"c";
    static NSString* valueKey = @"v";
    NSArray* romanNumerals = @[
        @{
            characterKey: @"I",
            valueKey: @1
        },
        @{
            characterKey: @"IV",
            valueKey: @4
            },
        @{
            characterKey: @"V",
            valueKey: @5
        },
        @{
            characterKey: @"IX",
            valueKey: @9
        },
        @{
            characterKey: @"X",
            valueKey: @10
        },
        @{
            characterKey: @"XL",
            valueKey: @40
        },
        @{
            characterKey: @"L",
            valueKey: @50
        },
        @{
            characterKey: @"XC",
            valueKey: @90
        },
        @{
            characterKey: @"C",
            valueKey: @100
        },
        @{
            characterKey: @"CD",
            valueKey: @400
        },
        @{
            characterKey: @"D",
            valueKey: @500
        },
        @{
            characterKey: @"CM",
            valueKey: @900
        },
        @{
            characterKey: @"M",
            valueKey: @1000
        }
    ];
    
    NSString* romanizedString = @"";
    NSInteger remainder = self.integerValue;
    
    for (NSInteger i = romanNumerals.count - 1; i >= 0; i--) {
        NSDictionary* numeral = romanNumerals[i];
        NSInteger value = ((NSNumber*)(numeral[valueKey])).integerValue;
        NSUInteger timesFit = remainder / value;
        
        if (timesFit > 0) {
            romanizedString = [romanizedString
                stringByAppendingString:[NSNumber
                    stringWithUnit:numeral[characterKey]
                    repeated:timesFit
                ]
            ];
            remainder -= timesFit * value;
        }
        
        if (remainder <= 0) {
            break;
        }
    }
    
    return romanizedString;
}

+ (NSString*)stringWithUnit:(NSString*)unit repeated:(NSUInteger)repeatCount
{
    NSString* repeatedString = @"";
    for (NSUInteger i = 0; i < repeatCount; i++) {
        repeatedString = [repeatedString stringByAppendingString:unit];
    }
    return repeatedString;
}

@end