从Go中的另一个嵌套结构变量访问结构的变量

Question

Given are 2 structs I wrote.

type DNSPacket struct {
    header      DNSHeader.DNSHeader
    questions   []DNSQuestion.DNSQuestion
    answers     []DNSRecord.DNSRecord
    authorities []DNSRecord.DNSRecord
    resources   []DNSRecord.DNSRecord
}

type DNSHeader struct {
    id uint16 //16bits

    recursion_desired    bool  // 1 bit
    truncated_message    bool  // 1 bit
    authoritative_answer bool  // 1 bit
    opcode               uint8 // 4 bits
    response             bool  // 1 bit

    rescode             ResultCode // 4 bits
    checking_disabled   bool       // 1 bit
    authed_data         bool       // 1 bit
    z                   bool       // 1 bit
    recursion_available bool       // 1 bit

    questions             uint16 // 16 bits
    answers               uint16 // 16 bits
    authoritative_entries uint16 // 16 bits
    resource_entries      uint16 // 16 bits
} // total 96 bits

Now, when I call results.header.questions where results is a type DNSPacket variable I get a [go] result.header.questions undefined (cannot refer to unexported field or method questions) error.

What am I doing wrong? Is there a workaround?

Thanks.

Answer 1

There are some issues here:

1. The fields of both your structs are not exported outside the package that contains them, because they begin with a lowercase letter. If you want to access fields outside of the package, they have to start with an uppercase letter.
2. Name your packages in lowercase, like dnsheader, not DNSHeader.

Read the spec on exported names and Effective Go on package names