创建一个NSString的类拓展即可：
// NSString+Comma.h
#import <Foundation/Foundation.h>
@interface NSString (Comma)
+(NSString*)strmethodComma:(NSString*)string;
@end
import "NSString+Comma.h"
@implementation NSString (Comma)
+(NSString*)strmethodComma:(NSString*)str
{
NSString *intStr;
NSString *floStr;
if ([str containsString:@"."]) {
NSRange range = [str rangeOfString:@"."];
floStr = [str substringFromIndex:range.location];
intStr = [str substringToIndex:range.location];
}else{
floStr = @"";
intStr = str;
}
if (intStr.length <=3) {
return [intStr stringByAppendingString:floStr];
}else{
NSInteger length = intStr.length;
NSInteger count = length/3;
NSInteger y = length%3;
NSString *tit = [intStr substringToIndex:y] ;
NSMutableString *det = [[intStr substringFromIndex:y] mutableCopy];
for (int i =0; i < count; i ++) {
NSInteger index = i + i *3;
[det insertString:@","atIndex:index];
}
if (y ==0) {
det = [[det substringFromIndex:1]mutableCopy];
}
intStr = [tit stringByAppendingString:det];
return [intStr stringByAppendingString:floStr];
}
}
@end
