Plugin symbol
- Go course
- Advanced
- Lesson 22/68
- 4 min
Learn to get an exported symbol with Lookup.
Using the symbol
The result of Lookup is a plugin.Symbol. For a function you type-assert to the function type; for a variable, to a pointer to its type:
selam := sym.(func(string) string)
fmt.Println(selam("Ada"))
surum := vsym.(*string) // pointer for a variable
fmt.Println(*surum)A contract through interfaces
A tidier approach: the plugin exports a value that satisfies an interface and the main program asserts to that interface. The interface is defined in a shared package:
type Komut interface { Calistir() string }
k := sym.(Komut)
fmt.Println(k.Calistir())Practice Type assertion
Declare var sym any = func(n int) int { return n + 1 } to imitate a plugin symbol. Convert it with sym.(func(int) int) and print f(9).
Starter code
package main
import "fmt"
func main() {
// buraya yaz
}Sample solution
package main
import "fmt"
func main() {
var sym any = func(n int) int { return n + 1 }
f := sym.(func(int) int)
fmt.Println(f(9))
}Expected output
10
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 If the plugin has <code>var Surum = "1.0"</code>, which type is the Lookup result asserted to?
- string
- func() string
- []byte
- *string Correct answer
Explanation: Variable symbols come back as pointers, so the main program can read and change the variable.
2 Convert to a function
f := sym.(____)
fmt.Println(f(3))f := sym.(func(int) int)
fmt.Println(f(3))Explanation: A function symbol is type-asserted to its own signature.
3 Symbol and assertion
| Term | Meaning |
|---|---|
func Selam(string) string |
func(string) string |
var Surum string |
*string |
var Sayac int |
*int |
var Eklenti Komut |
The Komut interface |