Number of occurrences of a substring in an NSString?

How can I get the number of times an NSString (for example, @"cake" ) appears in a larger NSString (for example, @"Cheesecake, apple cake, and cherry pie" )?

I need to do this on a lot of strings, so whatever method I use would need to be relatively fast.

Thanks!

---

这没有经过测试，但应该是一个好的开始。

NSUInteger count = 0, length = [str length];
NSRange range = NSMakeRange(0, length); 
while(range.location != NSNotFound)
{
  range = [str rangeOfString: @"cake" options:0 range:range];
  if(range.location != NSNotFound)
  {
    range = NSMakeRange(range.location + range.length, length - (range.location + range.length));
    count++; 
  }
}

---

A regex like the one below should do the job without a loop interaction...

Edited

NSString *string = @"Lots of cakes, with a piece of cake.";
NSError *error = NULL;
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:@"cake" options:NSRegularExpressionCaseInsensitive error:&error];
NSUInteger numberOfMatches = [regex numberOfMatchesInString:string options:0 range:NSMakeRange(0, [string length])];
NSLog(@"Found %i",numberOfMatches);

Only available on iOS 4.x and superiors.

---

was searching for a better method then mine but here's another example:

NSString *find = @"cake";
NSString *text = @"Cheesecake, apple cake, and cherry pie";

NSInteger strCount = [text length] - [[text stringByReplacingOccurrencesOfString:find withString:@""] length];
strCount /= [find length];

I would like to know which one is more effective.

And I made an NSString category for better usage:

// NSString+CountString.m

@interface NSString (CountString)
- (NSInteger)countOccurencesOfString:(NSString*)searchString;
@end

@implementation NSString (CountString)
- (NSInteger)countOccurencesOfString:(NSString*)searchString {
    NSInteger strCount = [self length] - [[self stringByReplacingOccurrencesOfString:searchString withString:@""] length];
    return strCount / [searchString length];
}
@end

simply call it by:

[text countOccurencesOfString:find];

Optional: you can modify it to search case insensitive by defining options:

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