README
¶
structconfig
Map default values, environment variables, and command-line arguments to struct tags.
Installation
go get github.com/berquerant/structconfig
Examples
Default values
type T struct {
I int `default:"10"`
}
sc := structconfig.New[T]()
var got T
if err := sc.FromDefault(&got); err != nil {
panic(err)
}
// got.I == 10
Environment variables
type T struct {
I int `name:"int_value"`
}
os.Setenv("INT_VALUE", "10")
sc := structconfig.New[T]()
var got T
if err := sc.FromEnv(&got); err != nil {
panic(err)
}
// got.I == 10
Command-line flags (pflag)
type T struct {
I int `name:"int_value" default:"10"`
}
var fs *pflag.FlagSet = // ...
sc := structconfig.New[T]()
if err := sc.SetFlags(fs); err != nil {
panic(err)
}
if err := fs.Parse([]string{"--int_value", "100"}); err != nil {
panic(err)
}
var got T
if err := sc.FromFlags(&got, fs); err != nil {
panic(err)
}
// got.I == 100
More examples
Documentation
¶
Index ¶
- Constants
- Variables
- func IsSupportedKind(k reflect.Kind) bool
- type AnyCallbackFunc
- type AnyEqualFunc
- type AnyReceptor
- type BoolReceptor
- type Config
- type ConfigBuilder
- type ConfigItem
- type EnvVar
- type FloatReceptor
- type IntReceptor
- type Merger
- type Option
- type Receptor
- type StringReceptor
- type StructConfig
- type StructField
- type Supported
- type Tag
- type Type
- type UintReceptor
- type Unsigned
Examples ¶
Constants ¶
View Source
const ( TagName = internal.TagName TagUsage = internal.TagUsage TagDefault = internal.TagDefault TagShort = internal.TagShort )
Variables ¶
View Source
var ( ErrStructConfig = internal.ErrStructConfig ErrNotStruct = internal.ErrNotStruct ErrNotStructPointer = internal.ErrNotStructPointer )
Functions ¶
func IsSupportedKind ¶
Types ¶
type AnyCallbackFunc ¶
type AnyCallbackFunc = func(StructField, string, func() reflect.Value) error
type AnyEqualFunc ¶
type AnyReceptor ¶
type AnyReceptor = internal.AnyReceptor
type BoolReceptor ¶
type BoolReceptor = internal.BoolReceptor
type Config ¶
type Config struct {
AnyCallback *ConfigItem[AnyCallbackFunc]
AnyEqual *ConfigItem[AnyEqualFunc]
Prefix *ConfigItem[string]
}
type ConfigBuilder ¶
type ConfigBuilder struct {
// contains filtered or unexported fields
}
func NewConfigBuilder ¶
func NewConfigBuilder() *ConfigBuilder
func (*ConfigBuilder) AnyCallback ¶
func (s *ConfigBuilder) AnyCallback(v AnyCallbackFunc) *ConfigBuilder
func (*ConfigBuilder) AnyEqual ¶
func (s *ConfigBuilder) AnyEqual(v AnyEqualFunc) *ConfigBuilder
func (*ConfigBuilder) Build ¶
func (s *ConfigBuilder) Build() *Config
func (*ConfigBuilder) Prefix ¶
func (s *ConfigBuilder) Prefix(v string) *ConfigBuilder
type ConfigItem ¶
type ConfigItem[T any] struct { // contains filtered or unexported fields }
func NewConfigItem ¶
func NewConfigItem[T any](defaultValue T) *ConfigItem[T]
func (*ConfigItem[T]) Default ¶
func (s *ConfigItem[T]) Default() T
func (*ConfigItem[T]) Get ¶
func (s *ConfigItem[T]) Get() T
func (*ConfigItem[T]) IsModified ¶
func (s *ConfigItem[T]) IsModified() bool
func (*ConfigItem[T]) Set ¶
func (s *ConfigItem[T]) Set(value T)
type FloatReceptor ¶
type FloatReceptor = internal.FloatReceptor
type IntReceptor ¶
type IntReceptor = internal.IntReceptor
type Merger ¶
Example ¶
package main
import (
"encoding/json"
"errors"
"fmt"
"reflect"
"github.com/berquerant/structconfig"
)
func main() {
type T struct {
I int `default:"1"`
S string `default:"s"`
II []int `default:"[1]"`
}
callback := func(s structconfig.StructField, v string, fv func() reflect.Value) error {
if s.Name() != "II" {
return errors.New("unexpected field name")
}
var xs []int
if err := json.Unmarshal([]byte(v), &xs); err != nil {
return err
}
fv().Set(reflect.ValueOf(xs))
return nil
}
eq := func(a, b any) (bool, error) {
// expect only []int because int and string are supported by structconfig
xs, ok := a.([]int)
if !ok {
return false, nil
}
ys, ok := b.([]int)
if !ok {
return false, nil
}
if len(xs) != len(ys) {
return false, nil
}
for i, x := range xs {
if x != ys[i] {
return false, nil
}
}
return true, nil
}
m := structconfig.NewMerger[T](
structconfig.WithAnyCallback(callback),
structconfig.WithAnyEqual(eq),
)
got, err := m.Merge(
T{
I: 100,
S: "s", // default
II: []int{100},
},
T{
I: 1, // default
S: "win",
II: []int{1}, // default
},
)
if err != nil {
panic(err)
}
fmt.Println(got.I, got.S, got.II)
}
Output: 100 win [100]
type Option ¶
type Option func(*Config)
func WithAnyCallback ¶
func WithAnyCallback(v AnyCallbackFunc) Option
func WithAnyEqual ¶
func WithAnyEqual(v AnyEqualFunc) Option
func WithPrefix ¶
type StringReceptor ¶
type StringReceptor = internal.StringReceptor
type StructConfig ¶
type StructConfig[T any] struct { // contains filtered or unexported fields }
func New ¶
func New[T any](opt ...Option) *StructConfig[T]
New returns a new StructConfig.
AnyCallback parses "default" tag value and set it. Prefix adds a prefix to "name", "short", "default" and "usage" tag name.
func (StructConfig[T]) FromDefault ¶
func (sc StructConfig[T]) FromDefault(v *T) error
FromDefault sets "default" tag values to v.
Example ¶
package main
import (
"fmt"
"github.com/berquerant/structconfig"
)
func main() {
type T struct {
B bool `default:"false"`
I int
F float32 `default:"1.1"`
S string `default:"str"`
}
sc := structconfig.New[T]()
var got T
if err := sc.FromDefault(&got); err != nil {
panic(err)
}
fmt.Println(got.B, got.I, got.F, got.S)
}
Output: false 0 1.1 str
func (StructConfig[T]) FromEnv ¶
func (sc StructConfig[T]) FromEnv(v *T) error
FromEnv sets environment variable values to v.
Environment variable name will be
NewEnvVar("name tag value").String()
All '.' and '-' will be replaced with '_', making it all uppsercase.
Example ¶
package main
import (
"fmt"
"os"
"github.com/berquerant/structconfig"
)
func main() {
type T struct {
B bool `name:"bool_value"`
S string `name:"string_value"`
N int `name:"int_value" default:"10"`
N2 int
N3 int `name:"-"`
}
envs := map[string]string{
"BOOL_VALUE": "true",
"STRING_VALUE": "str",
}
for k, v := range envs {
os.Setenv(k, v)
}
defer func() {
for k := range envs {
os.Unsetenv(k)
}
}()
sc := structconfig.New[T]()
var got T
if err := sc.FromEnv(&got); err != nil {
panic(err)
}
fmt.Println(got.B, got.S, got.N, got.N2, got.N3)
}
Output: true str 10 0 0
func (StructConfig[T]) FromFlags ¶
func (sc StructConfig[T]) FromFlags(v *T, fs *pflag.FlagSet) error
FromFlags sets values to v from command-line flags.
Flag name is from "name" tag value.
Example ¶
package main
import (
"errors"
"fmt"
"reflect"
"sort"
"strings"
"github.com/berquerant/structconfig"
"github.com/spf13/pflag"
)
func main() {
type T struct {
B bool `name:"bool_value" usage:"BOOL"`
S string `name:"string_value" default:"str"`
X bool `name:"bool_short" short:"x"`
Ignore1 int
Ignore2 int `name:"-"`
V struct {
S string
} `name:"struct_value"`
}
anyCallback := func(s structconfig.StructField, v string, fv func() reflect.Value) error {
if x, ok := s.Tag().Name(); !ok || x != "struct_value" {
// among T, only struct_value is not supported
return errors.New("unexpected tag name")
}
fv().Set(reflect.ValueOf(struct {
S string
}{
S: v,
}))
return nil
}
fs := pflag.NewFlagSet("test", pflag.ContinueOnError)
sc := structconfig.New[T](structconfig.WithAnyCallback(anyCallback))
if err := sc.SetFlags(fs); err != nil {
panic(err)
}
flagNames := []string{}
fs.VisitAll(func(f *pflag.Flag) {
flagNames = append(flagNames, f.Name)
})
if err := fs.Parse([]string{"--bool_value", "--struct_value", "sv", "-x"}); err != nil {
panic(err)
}
var got T
if err := sc.FromFlags(&got, fs); err != nil {
panic(err)
}
sort.Strings(flagNames)
fmt.Println(strings.Join(flagNames, ","))
fmt.Println(got.B, got.S, got.Ignore1, got.Ignore2, got.V.S, got.X)
}
Output: bool_short,bool_value,string_value,struct_value true str 0 0 sv true
Example (Prefix) ¶
package main
import (
"fmt"
"sort"
"strings"
"github.com/berquerant/structconfig"
"github.com/spf13/pflag"
)
func main() {
tagPrefix := "sc"
type T struct {
B bool `scname:"bool_value" scusage:"BOOL"`
S string `scname:"string_value" scdefault:"str"`
}
fs := pflag.NewFlagSet("test", pflag.ContinueOnError)
sc := structconfig.New[T](structconfig.WithPrefix(tagPrefix))
if err := sc.SetFlags(fs); err != nil {
panic(err)
}
flagNames := []string{}
fs.VisitAll(func(f *pflag.Flag) {
flagNames = append(flagNames, f.Name)
})
if err := fs.Parse([]string{"--bool_value", "--string_value", "sv"}); err != nil {
panic(err)
}
var got T
if err := sc.FromFlags(&got, fs); err != nil {
panic(err)
}
sort.Strings(flagNames)
fmt.Println(strings.Join(flagNames, ","))
fmt.Println(got.B, got.S)
}
Output: bool_value,string_value true sv
type StructField ¶
type StructField = internal.StructField
type UintReceptor ¶
type UintReceptor = internal.UintReceptor
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