Golang change type of pointer interface

Question

I have a function which returns a slice of pointers of some interface. I want to change the type later in the code to the implementation type but nothing works, I still get an invalid type assertion.

Example

func Test(c Parsable)([]*Parsable, error) {
   // generate slice by factory method on Parsable inteface and return slice
}

var implParsable ImplParsable
results, err := Test(implParsable) 

data := results[0].(ImplParsable) // I tried this in many variations but nothing works

If it's a pointer you just need to dereference it (*), but are you sure you actually want to be using a pointer to to an interface? There is usually no ready to do so. — Mr_Pink
– Mr_Pink, Commented Aug 16, 2018 at 17:34
I try it also with * but not working, and I have function where I use it as factory, I add the function for more explanation of problem — Sebastian
– Sebastian, Commented Aug 16, 2018 at 17:37

Mr_Pink · Accepted Answer · 2018-08-16 17:39:37Z

3

resultSets[0] is a pointer to an interface, so you need to dereference that pointer to get the interface value, which you can do inline since slice values are addressable.

data :=  (*resultSets[0]).(ImplParsable)

answered Aug 16, 2018 at 17:39

Mr_Pink

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