Golang: loop through fields of a struct modify them and and return the struct?

Question

I am trying to loop through the individual fields of a struct applying a function to each field and then return the original struct as a whole with the modified field values. Obviously, this would not present a challenge if it were for one struct but I need the function to be dynamic. For this instance, I am referencing the Post and Category struct as shown below ``` type Post struct{ fieldName data `check:"value1" ... } type Post struct{ fieldName data `check:"value2" ... } ``` I then have a switch function that loops through the respective fields of the structs and depending on what value the `check` has, applies a function to that field's `data` as follows ``` type Datastore interface { ... } func CheckSwitch(value reflect.Value){ //this loops through the fields for i := 0; i < value.NumField(); i++ { // iterates through every struct type field tag := value.Type().Field(i).Tag // returns the tag string field := value.Field(i) // returns the content of the struct type field switch t…

Accepted Answer

The variable `field` has type `reflect.Value`. Call the Set* methods on `field` to set the fields in the struct. For example:

```
 field.SetString("hello")
```

sets the the struct field to "hello".

You must pass a pointer to the struct if you want to retain the values:

```
function foo(){ 
    p:=Post{fieldName:"bar"} 
    check(&p)
}

func check(d Datastore){
   value := reflect.ValueOf(d)
   if value.Kind() != reflect.Ptr {
      // error
   }
   CheckSwitch(value.Elem())
   ...
}
```

Also, the field names must be exported.

playground example

Golang: loop through fields of a struct modify them and and return the struct?

Solution

Problem