76 lines
2.3 KiB
Markdown
76 lines
2.3 KiB
Markdown
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defaults
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========
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[](https://circleci.com/gh/creasty/defaults/tree/master)
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[](https://codecov.io/gh/creasty/defaults)
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[](https://github.com/creasty/defaults/releases)
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[](./LICENSE)
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Initialize structs with default values
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- Supports almost all kind of types
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- Scalar types
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- `int/8/16/32/64`, `uint/8/16/32/64`, `float32/64`
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- `uintptr`, `bool`, `string`
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- Complex types
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- `map`, `slice`, `struct`
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- Nested types
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- `map[K1]map[K2]Struct`, `[]map[K1]Struct[]`
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- Aliased types
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- `time.Duration`
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- e.g., `type Enum string`
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- Pointer types
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- e.g., `*SampleStruct`, `*int`
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- Recursively initializes fields in a struct
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- Dynamically sets default values by [`defaults.Setter`](./setter.go) interface
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- Preserves non-initial values from being reset with a default value
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Usage
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-----
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```go
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type Gender string
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type Sample struct {
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Name string `default:"John Smith"`
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Age int `default:"27"`
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Gender Gender `default:"m"`
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Slice []string `default:"[]"`
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SliceByJSON []int `default:"[1, 2, 3]"` // Supports JSON
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Map map[string]int `default:"{}"`
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MapByJSON map[string]int `default:"{\"foo\": 123}"`
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MapOfStruct map[string]OtherStruct
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MapOfPtrStruct map[string]*OtherStruct
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MapOfStructWithTag map[string]OtherStruct `default:"{\"Key1\": {\"Foo\":123}}"`
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Struct OtherStruct `default:"{}"`
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StructPtr *OtherStruct `default:"{\"Foo\": 123}"`
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NoTag OtherStruct // Recurses into a nested struct by default
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OptOut OtherStruct `default:"-"` // Opt-out
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}
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type OtherStruct struct {
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Hello string `default:"world"` // Tags in a nested struct also work
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Foo int `default:"-"`
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Random int `default:"-"`
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}
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// SetDefaults implements defaults.Setter interface
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func (s *OtherStruct) SetDefaults() {
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if defaults.CanUpdate(s.Random) { // Check if it's a zero value (recommended)
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s.Random = rand.Int() // Set a dynamic value
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}
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}
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```
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```go
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obj := &Sample{}
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if err := defaults.Set(obj); err != nil {
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panic(err)
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}
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```
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