输入网址，字符串检查

检查输入的地址是不网址，是否带开头http
方法可以直接用

-(NSURL *)smartURLForString:(NSString *)str
{
 

   NSURL*result;
    NSString*trimmedStr;
    NSRangeschemeMarkerRang;
    NSString*scheme;
    
    assert(str!= nil);
    
    result =nil;
    
    trimmedStr =[str stringByTrimmingCharactersInSet:[NSCharacterSetwhitespaceCharacterSet]];
    if((trimmedStr != nil) &&(trimmedStr.length != 0))
    {
      schemeMarkerRang = [trimmedStrrangeOfString:@"://"];
      
      if (schemeMarkerRang.location ==NSNotFound)
      {
         result = [NSURL URLWithString:[NSStringstringWithFormat:@"http://%@",trimmedStr]];
      }
      else {
         scheme = [trimmedStrsubstringWithRange:NSMakeRange(0,schemeMarkerRang.location)];
         assert(scheme != nil);
         if (([scheme compare:@"http"options:NSCaseInsensitiveSearch] == NSOrderedSame)
            || ([scheme compare:@"https"options:NSCaseInsensitiveSearch] == NSOrderedSame))
         {
            result = [NSURL URLWithString:trimmedStr];
         }
         else {
            
         }
      }
    }
    returnresult;
}