Objective-C CF Random Name Generator

Based on a python name generator grammar I found here I've decided to write my own in objective-C. The idea is I can load the grammar from a plist file and generate random names from it.

I'm looking for a general code review and any comments and or suggestions.

NameGenerator.h:

@interface NameGenerator : NSObject
- (id)initWithGrammar:(NSString *)plistName;
- (NSString*)name;
@end

NameGenerator.m:

@interface NameGenerator()
@property (nonatomic,strong) NSDictionary *grammar;
-(NSString*)replaceKey:(NSString*)input;
@end

@implementation NameGenerator
@synthesize grammar = _grammar;

- (id)init {
    @throw [NSException exceptionWithName: @"NameGeneratorInit"
                                   reason: @"-init is not allowed, use -initWithGrammar: instead"
                                 userInfo: nil];
}

- (id)initWithGrammar:(NSString *)plistName
{
    self = [super init];
    if (self) {
        NSString* plistPath = [[NSBundle mainBundle] pathForResource:plistName ofType:@"plist"];
        self.grammar = [NSDictionary dictionaryWithContentsOfFile:plistPath];

        id object = [self.grammar objectForKey:@"grammar"];
        if (![object isKindOfClass:[NSString class]]) {
            NSLog(@"initWithGrammar: Not a grammar plist");
            self = nil;
        }

        NSString *ver = object;
        if (![ver isEqualToString:@"NG.CF.1"]) {
            NSLog(@"initWithGrammar: plist version is wrong");
            self = nil;
        }
    }
    return self;
}

- (NSString*)name {
    return [self replaceKey:@"name"];
}

-(NSString*)replaceKey:(NSString*)input
{
    NSString *output = @"";
    NSArray *parts = [input componentsSeparatedByString:@","];

    if ([parts count] > 1) {
        for(NSString *part in parts) {
            output = [output stringByAppendingString:[self replaceKey:part]];
        }
    } else {
        id object = [self.grammar objectForKey:input];
        if ([object isKindOfClass:[NSString class]]) {
            output = [self replaceKey:object];
        }
        else if ([object isKindOfClass:[NSArray class]]) {
            NSUInteger randomIndex = arc4random() % [object count];
            output = [self replaceKey:[object objectAtIndex:randomIndex]];
        }
        else {
            output = input;
        }
    }

    return output;
}

ork.plist:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>grammar</key>
    <string>NG.CF.1</string>
    <key>name</key>
    <string>nameStart,nameMiddle0to3,nameEnd</string>
    <key>nameMiddle0to3</key>
    <array>
        <string></string>
        <string>nameMiddle</string>
        <string>nameMiddle,nameMiddle</string>
        <string>nameMiddle,nameMiddle,nameMiddle</string>
    </array>
    <key>nameStart</key>
    <array>
        <string>nsCons,tick,nsCons,nmVowel</string>
        <string>nsCons,nmVowel</string>
        <string>nsCons,nmVowel</string>
        <string>nsCons,nmVowel</string>
        <string>nsVowel</string>
    </array>
    <key>nameMiddle</key>
    <string>nmCons,nmVowel</string>
    <key>nameEnd</key>
    <array>
        <string>neCons,neVowel</string>
        <string>neCons</string>
        <string>neCons</string>
    </array>
    <key>nsCons</key>
    <array>
        <string>d</string>
        <string>g</string>
        <string>k</string>
        <string>t</string>
        <string>gr</string>
    </array>
    <key>nmCons</key>
    <array>
        <string>d</string>
        <string>g</string>
        <string>k</string>
        <string>t</string>
        <string>r</string>
        <string>s</string>
        <string>z</string>
        <string>kt</string>
        <string>rs</string>
        <string>gr</string>
    </array>
    <key>neCons</key>
    <array>
        <string>r</string>
        <string>s</string>
        <string>z</string>
    </array>
    <key>nsVowel</key>
    <array>
        <string>e</string>
        <string>u</string>
    </array>
    <key>nmVowel</key>
    <array>
        <string>a</string>
        <string>e</string>
        <string>i</string>
        <string>o</string>
        <string>u</string>
    </array>
    <key>neVowel</key>
    <array>
        <string>a</string>
        <string>u</string>
    </array>
    <key>tick</key>
    <array>
        <string>&apos;</string>
    </array>
</dict>
</plist>