url组成

 ://[username:password@]/[;][?]#

    NSURL*url=[NSURL URLWithString:@"asdfa://user:password@host:8080/path1/path2;asdfasf=advasdf&asdfalll;;;;=asdf22;parameters3;;;;;;;parmater4;;?key=value&key2=value2#fragmentasd=2asdfas123&&&&fas=12121"];
    NSLog(@"%@",url.resourceSpecifier);
    NSLog(@"%@",url.scheme);
    NSLog(@"%@",url.user);
    NSLog(@"%@",url.password);
    NSLog(@"%@",url.host);
    NSLog(@"%@",url.port);
    NSLog(@"%@",url.path);
    NSLog(@"%@",url.parameterString);
    NSLog(@"%@",url.query);
    NSLog(@"%@",url.fragment);



输出结果：
//user:password@host:8080/path1/path2;asdfasf=advasdf&asdfalll;;;;=asdf22;parameters3;;;;;;;parmater4;;?key=value&key2=value2#fragmentasd=2asdfas123&&&&fas=12121
 asdfa
 user
 password
 host
 8080
 /path1/path2
 asdfasf=advasdf&asdfalll;;;;=asdf22;parameters3;;;;;;;parmater4;;
 key=value&key2=value2
 fragmentasd=2asdfas123&&&&fas=12121