godefault
Enabling stuctures with godefault values using struct tags.
The recommended way to install godefault
go get github.com/sonnt85/godefault
A basic example:
import (
"fmt"
"github.com/sonnt85/godefault"
"time"
)
type ExampleBasic struct {
Foo bool `default:"true"` //<-- StructTag with a default key
Bar string `default:"33"`
Qux int8
Dur time.Duration `default:"1m"`
}
func NewExampleBasic() *ExampleBasic {
example := new(ExampleBasic)
godefault.SetDefaults(example) //<-- This set the godefault values
return example
}
...
test := NewExampleBasic()
fmt.Println(test.Foo) //Prints: true
fmt.Println(test.Bar) //Prints: 33
fmt.Println(test.Qux) //Prints:
fmt.Println(test.Dur) //Prints: 1m0sAt the moment, the way the default filler checks whether it should fill a struct field or not is by comparing the current field value with the corresponding zero value of that type. This has a subtle implication: the zero value set explicitly by you will get overriden by default value during SetDefaults() call. So if you need to set the field to container zero value, you need to set it explicitly AFTER setting the godefault.
Take the basic example in the above section and change it slightly:
example := ExampleBasic{
Bar: 0,
}
godefault.SetDefaults(example)
fmt.Println(example.Bar) //Prints: 33 instead of 0 (which is zero value for int)
example.Bar = 0 // set needed zero value AFTER applying godefault
fmt.Println(example.Bar) //Prints: 0MIT, see LICENSE