附加到实现的基本接口部分

Question

Why the below doesn't work?

locations := make([]*LocationEvent, 0)
data := make([]Event, 0)
data = append(data, locations...)

where *LocationEvent (struct) implements Event (interface).

While the below works fine:

data = append(data, &LocationEvent{}, &LocationEvent{})

So how it is different when expanding the actual []*LocationEvent slice using ...?

Answer 1

The slice type must match the type of the variadic arguments in the append function exactly. locations is of type []*LocationEvent, and thus not compatible with []Event. There is no automatic "downcasting" in Go when working with slices.

You have to copy the locations to a new slice of Event, or add the items of locations one-by-one to the data slice.

For more explanation look here: https://stackoverflow.com/a/12754757/6655315