add: type switch

interfaces/06-empty-interface/empty2/main.go

@@ -0,0 +1,43 @@
+// For more tutorials: https://blog.learngoprogramming.com
+//
+// Copyright © 2018 Inanc Gumus
+// Learn Go Programming Course
+// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
+//
+
+package main
+
+import "fmt"
+
+func main() {
+	nums := []int{1, 2, 3}
+
+	// Store a slice in `any`
+	var any interface{}
+	any = nums
+
+	// `any` is an empty interface value, it's not a slice.
+	// You cannot get its length. It has no length.
+	// _ = len(any)
+
+	// When you extract the slice from it, you can get the slice's length.
+	_ = len(any.([]int))
+
+	// You cannot assign an `[]T` slice to `[]interface{}` slice.
+	// Where `T` can be of any type.
+	// Reason: `[]interface{}` is a slice, it's not an `empty interface` value.
+	var many []interface{}
+	// many = nums
+
+	// The same reason that you can't assign an `[]int` to a `[]string`.
+	// var words []string = nums
+
+	// You need to copy the elements from `nums` to `many` manually.
+	for _, n := range nums {
+		many = append(many, n)
+	}
+	fmt.Println(many)
+
+	// Each element of the `many` slice is an `empty interface` value.
+	// el := many[0]
+}