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)?

Switch Case can be a simple solution.

Rajan
– Rajan

2022-01-08 11:07:38 +00:00
Commented Jan 8, 2022 at 11:07 — Rajan
– Rajan, Commented Jan 8, 2022 at 11:07

Community · Accepted Answer · 2017-05-23 11:54:22Z

26

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)

edited May 23, 2017 at 11:54

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answered Mar 20, 2017 at 15:19

icza

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4 Comments

MohNj Over a year ago

how to add arguments to MyFunc?

icza Over a year ago

@MohNj Like this: func (m My) MyFunc(paramName paramType) {}

karthikeyan Over a year ago

Is there a way I can call them without reflection? I was thinking of adapter pattern. Any thoughts on the same?

icza Over a year ago

@karthikeyan The linked question shows other ways to call it: Call functions with special prefix/suffix

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