Calling method of named type

Question

I have a named type, which I needed to make to do some JSON unmarshmaling:

type StartTime time.Time
func (st *StartTime) UnmarshalJSON(b []byte) error {...}


        

Answer 1

Using the type keyword you are creating a new type and as such it will not have the methods of the underlying type.

Use embedding:

type StartTime struct {
    time.Time
}

Quoting from the Spec: Struct types:

A field or method f of an anonymous field in a struct x is called promoted if x.f is a legal selector that denotes that field or method f.

So all the methods and fields of the embedded (anonymous) fields are promoted and can be referred to.

Example using it:

type StartTime struct {
    time.Time
}

func main() {
    s := StartTime{time.Now()}
    fmt.Println(s.Date())
}

Output (try it on the Go Playground):

2009 November 10