Method undefined (type has no method) - class

Question

If I try a file like this:
package main
import "time"
type Alpha time.Time
func main() {
o := Alpha.Now()
n := o.Unix()
println(n)
}
I get this result:
Alpha.Now undefined (type Alpha has no method Now)
However it works with other languages. For example PHP:
<?php
class Alpha extends DateTime {}
$o = new Alpha;
$n = $o->getTimestamp();
var_dump($n);
It is possible with Go, to create a new type that has access to the methods of
another type?

Answer 1

First of all, time.Now() is just a package-level function, not a method of any type. Thus, the proper way to invoke it would look like smth := time.Time(), not smth := time.Time.Now().
We can take a closer look at the function. It's defined in package time and currently implemented as follows:
func Now() Time {
sec, nsec, mono := now()
mono -= startNano
sec += unixToInternal - minWall
if uint64(sec)>>33 != 0 {
return Time{uint64(nsec), sec + minWall, Local}
}
return Time{hasMonotonic | uint64(sec)<<nsecShift | uint64(nsec), mono, Local}
}
As you can see, it returns an object of type time.Time. Which then can be used for the consequent .Unix() method call:
func (t Time) Unix() int64 {
return t.unixSec()
}
In case of Unix() it's a true method with the receiver of type time.Time.
For the extension part of your question, you can use the following trick:
package main
import "time"
type Alpha struct {
time.Time
}
func main() {
o := time.Now()
a := Alpha { o }
n := a.Unix()
println(n)
}
Go doesn't provide any model of inheritance. However, its composition capabilities are very powerful. The code from the snippet above basically creates a new struct type Alpha with an anonymous attribute of type time.Time. However, due to the fact that the explicit name of this attribute is skipped, we can access methods of a contained time.Time instance right through the parent structure. The technique is called Embedding.