defaults

README

defaults

Initialize structs with default values

• Supports almost all kind of types
  • Scalar types
    • int/8/16/32/64, uint/8/16/32/64, float32/64
    • uintptr, bool, string
  • Complex types
    • map, slice, struct
  • Nested types
    • map[K1]map[K2]Struct, []map[K1]Struct[]
  • Aliased types
    • time.Duration
    • e.g., type Enum string
  • Pointer types
    • e.g., *SampleStruct, *int
• Recursively initializes fields in a struct
• Dynamically sets default values by defaults.Setter interface
• Preserves non-initial values from being reset with a default value

Usage

type Gender string

type Sample struct {
	Name   string `default:"John Smith"`
	Age    int    `default:"27"`
	Gender Gender `default:"m"`

	Slice       []string       `default:"[]"`
	SliceByJSON []int          `default:"[1, 2, 3]"` // Supports JSON

	Map                 map[string]int `default:"{}"`
	MapByJSON           map[string]int `default:"{\"foo\": 123}"`
	MapOfStruct         map[string]OtherStruct
	MapOfPtrStruct      map[string]*OtherStruct
	MapOfStructWithTag  map[string]OtherStruct `default:"{\"Key1\": {\"Foo\":123}}"`
    
	Struct    OtherStruct  `default:"{}"`
	StructPtr *OtherStruct `default:"{\"Foo\": 123}"`

	NoTag  OtherStruct               // Recurses into a nested struct by default
	OptOut OtherStruct `default:"-"` // Opt-out
}

type OtherStruct struct {
	Hello  string `default:"world"` // Tags in a nested struct also work
	Foo    int    `default:"-"`
	Random int    `default:"-"`
}

// SetDefaults implements defaults.Setter interface
func (s *OtherStruct) SetDefaults() {
	if defaults.CanUpdate(s.Random) { // Check if it's a zero value (recommended)
		s.Random = rand.Int() // Set a dynamic value
	}
}

obj := &Sample{}
if err := defaults.Set(obj); err != nil {
	panic(err)
}

Documentation

Index

• func CanUpdate(v interface{}) bool
• func MustSet(ptr interface{})
• func Set(ptr interface{}) error
• type Setter

Functions

func CanUpdate

func CanUpdate(v interface{}) bool

CanUpdate returns true when the given value is an initial value of its type

func MustSet

func MustSet(ptr interface{})

MustSet function is a wrapper of Set function It will call Set and panic if err not equals nil.

func Set

func Set(ptr interface{}) error

Set initializes members in a struct referenced by a pointer. Maps and slices are initialized by `make` and other primitive types are set with default values. `ptr` should be a struct pointer

Types

type Setter

type Setter interface {
	SetDefaults()
}

Setter is an interface for setting default values