Golang : What is StructTag and how to get StructTag's value?
For those who code or read Golang's code and left wondering what are those string inside the '``'
such as xml:"firstname"
Such as these example below :
type Staff struct {
XMLName xml.Name `xml:"staff"`
ID int `xml:"id"`
FirstName string `xml:"firstname"`
LastName string `xml:"lastname"`
UserName string `xml:"username"`
}
type Company struct {
XMLName xml.Name `xml:"company"`
Staffs []Staff `xml:"staff"`
}
They are known as StructTag and you can process the tags with the reflect
package. In this example, we will extract the custom tags' value with field.Tag.Get()
method :
package main
import (
"encoding/xml"
"fmt"
"reflect"
)
func main() {
type Company struct {
XMLName xml.Name `xml:"company"`
}
c := Company{}
cType := reflect.TypeOf(c)
field := cType.Field(0)
xmlTag := field.Tag.Get("xml")
fmt.Println(xmlTag)
type S struct {
F string `species:"gopher" color:"pink"`
}
s := S{}
st := reflect.TypeOf(s)
field = st.Field(0)
fmt.Println(field.Tag.Get("color"), field.Tag.Get("species"))
}
Output :
company
pink gopher
One usage example that I can think of is that StructTag allows a developer to create her/his own custom tagging and use the tags to find the relevant field and extract value from the field.
Hope this short tutorials can be useful to you!
Reference :
See also : Golang : How to get struct field and value by name
By Adam Ng
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