Getting method parameter names

by

There is no way to get the names of the parameters of a method or a function.

The reason for this is because the names are not really important for someone calling a method or a function. What matters is the types of the parameters and their order.

A Function type denotes the set of all functions with the same parameter and result types. The type of 2 functions having the same parameter and result types is identical regardless of the names of the parameters. The following code prints true:

func f1(a int) {}
func f2(b int) {}

fmt.Println(reflect.TypeOf(f1) == reflect.TypeOf(f2))

It is even possible to create a function or method where you don’t even give names to the parameters (within a list of parameters or results, the names must either all be present or all be absent). This is valid code:

func NamelessParams(int, string) {
    fmt.Println("NamelessParams called")
}

For details and examples, see Is unnamed arguments a thing in Go?

If you want to create some kind of framework where you call functions passing values to “named” parameters (e.g. mapping incoming API params to Go function/method params), you may use a struct because using the reflect package you can get the named fields (e.g. Value.FieldByName() and Type.FieldByName()), or you may use a map. See this related question: Initialize function fields

Here is a relevant discussion on the golang-nuts mailing list.

More Related Contents:

  1. Go reflection with interface embedded in struct – how to detect “real” functions?
  2. What are the use(s) for tags in Go?
  3. What are the use(s) for struct tags in Go?
  4. How does Rust implement reflection?
  5. How to access unexported struct fields
  6. How to get Type representation from name via reflection?
  7. How do you create a new instance of a struct from its type at run time in Go?
  8. Scala: How do I dynamically instantiate an object and invoke a method using reflection?
  9. Identify non builtin-types using reflect
  10. Using reflect, how do you set the value of a struct field?
  11. range over interface{} which stores a slice
  12. How can I get the list of a columns in a table for a SQLite database?
  13. How do I call a Scala Object method using reflection?
  14. How to get type of the module in F#
  15. TypeOf without an instance and passing result to a func
  16. How to get the name of a function in Go?
  17. How do I get the path of the assembly the code is in?
  18. How do I programmatically compile and instantiate a Java class?
  19. json.Marshal(struct) returns “{}”
  20. cancel a blocking operation in Go
  21. Relative imports in Go
  22. Changing private final fields via reflection
  23. Check if a Class Object is subclass of another Class Object in Java
  24. Java Reflection calling constructor with primitive types
  25. Partly JSON unmarshal into a map in Go
  26. Find out which classes of a given API are used
  27. How to stop http.ListenAndServe()
  28. How can I install a package with go get?
  29. Convert slice of string to slice of pointer to string
  30. How to write a generic function that accepts any numerical type?

Leave a Comment