Golang中非原子类型的类型包装

Question

I'm new to golang and am trying to understand a code example of type wrapping for the "non-atomic" type time.Time.

The type extension in question is from the Go client for GDAX on github, go-coinbase-exchange project.

The expected behavior would be for Time variables from the project (coinbase.Time), which are of type Time time.Time (as defined in the project's time.go file) to behave something like the following example for extending the "atomic" type int (from blog.riff.org in that they might follow a kind of "inheritance" from the base type for functions like Time.format (from golang's standard implementation of time:

package main
import "fmt"
type Int int

func (i Int) Add(j Int) Int {
  return i + j
}

func main() {
  i := Int(5)
  j := Int(6)
  fmt.Println(i.Add(j))
  fmt.Println(i.Add(j) + 12)
}

But if I modify the code example from the project's List Account Ledger example found in Readme.md to include a print function which might otherwise give me a human-readable view of the CreatedAt struct variables (as follows), I get a compiler error saying that "type coinbase.Time has no field or method Format":

for _, e := range ledger {
    print("Entry Creation: ")
    fmt.Printf(e.CreatedAt.Format("2006-01-02 15:04:05.999999+00"))
}

The expected behavior inside the for loop would be for it to print the ledger entries in a human-readable format. I can get the contents of the structs, but I'm not really sure how to then use the resulting wall, ext and loc members.

For example, inserting fmt.Printf("%#v", e.CreatedAt) into the for loop gives me a representation of the time that looks something like this:

coinbase.Time{wall:0x3015a123, ext:63612345678, loc:(*time.Location)(nil)} {806986000 63638738354 <nil>}

I can also see that wall is of type uint64, that ext is of type int64 and that loc is just GMT/UTC=0 by formatting the variable as a string because fmt.Printf("%s", e.CreatedAt) gives me output which is similar to the following:

{%!s(uint64=712345678) %!s(int64=63612345678) %!s(*time.Location=<nil>)}

It seems like I'm missing something. I've requested further information through issues tab on github, but maybe this is a nube question. So I'm not sure how quick the response time would be, and I'm interested in the more general case for extending non-atomic types in go.

Answer 1

Named types do not inherit any methods from the underlying type (indeed there is no inheritance at all in Go); you must cast to the underlying type to call any methods from that type:

(time.Time(e.CreatedAt)).Format("2006-01-02 15:04:05.999999+00")