手机号码后N位改为“*”（类目）

@interface NSString (mima)

+(NSString*)mima:(NSMutableString*)string num:(int)num;

@end

@implementation NSString (mima)

+(NSString*)mima:(NSMutableString*)string num:(int)num;
{
    for (int i=0; i<num; i++)
    {
        [string replaceCharactersInRange:NSMakeRange([string length]-num+i, 1) withString:@"*"];
    }
    return string;
}


@end

 下面是使用：

    NSString*num=@"12345678";
    NSLog(@"===%@",[NSString mima:[num mutableCopy] num:4]);