How to call method by its string name with string struct name?

Question

I have one struct with 2 methods under struct definition, I want to call in other place that use struct's name and method's name as param.

Struct code as following:

type ArticleForm struct {
Name     string     `required:"true" pattern:"^[A-Za-z0-9\u4e00-\u9fa5]{1,1024}$" valid:"Required;MaxSize(1024)"`
Category []Category `class:"multis" required:"true" valid:"Required" optionqs:"GetCategoryOption"`
Content  string     `class:"wysiwg_area" required:"true" valid:"Required"`
Tags     []Tags     `class:"multis_create" optionqs:"GetTagOptions"`
}

Method definition as following:

func (this *ArticleForm) GetTagOptions() []Tags {
return GetTagsOptions(nil)
}

Following is what I want to call:

func main() {
s := "models.ArticleForm"
t := "GetTagOptions"
//following is the question, how can i exec following?
funcall(s,t)
}

How to fulfill the funcall(s,t)?

See http://stackoverflow.com/questions/10210188/instance-new-type-golang for creating an instance of a type given a string. — Charlie Tumahai, Mar 20 '17 at 18:24

score 23 · Answer 1 · edited May 23 '17 at 11:54

Calling a method of some type given by its name is easy (using reflection). See this example:

type My struct{}

func (m My) MyFunc() {
    fmt.Println("MyFunc called")
}

func main() {
    m := My{}
    meth := reflect.ValueOf(m).MethodByName("MyFunc")
    meth.Call(nil)
}

Output (try it on the Go Playground):

MyFunc called

"Instantiating" a type given its string name is not possible, because if your code does not explicitly refer to the type, it may not even be included in the executable binary. For details, see Call all functions with special prefix or suffix in Golang; and Splitting client/server code.

A possible workaround is to use some kind of "type-registry" which you populate prior to using it (before you want to create a value by its name). The type registry (which may be a map) may hold reflect.Type values or factory functions mapped from the type name.

Following the above My type declaration, a type registry storing reflect.Type values may look like this (try it on the Go Playground):

registry := map[string]reflect.Type{
    "My": reflect.TypeOf((*My)(nil)).Elem(),
}

v := reflect.New(registry["My"]).Elem()
v.MethodByName("MyFunc").Call(nil)

And a registry that stores factory functions could look like this (try it on the Go Playground):

registry := map[string]func() interface{}{
    "My": func() interface{} { return My{} },
}

v := registry["My"]()
meth := reflect.ValueOf(v).MethodByName("MyFunc")
meth.Call(nil)

@MohNj Like this: `func (m My) MyFunc(paramName paramType) {}` — icza, Sep 03 '22 at 17:44
Is there a way I can call them without reflection? I was thinking of adapter pattern. Any thoughts on the same? — karthikeyan, Dec 20 '22 at 07:47
@karthikeyan The linked question shows other ways to call it: [Call functions with special prefix/suffix](https://stackoverflow.com/questions/37384473/call-functions-with-special-prefix-suffix/37384665#37384665) — icza, Dec 20 '22 at 07:56

How to call method by its string name with string struct name?

1 Answers1