Golang Notes

Go

Structs do not have any empty value in Go.

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type dimension struct {
	Height int
	Width int
}

type Dog struct {
	Breed    string
	WeightKg int
	Size dimension `json:",omitempty"`
}

func main() {
	d := Dog{
		Breed: "pug",
	}
	b, _ := json.Marshal(d)
	fmt.Println(string(b))
}
// prints:
// {"Breed":"pug","WeightKg":0,"Size":{"Height":0,"Width":0}}

In this case, even though we never set the value of the Size attribute, and set its omitempty tag,it still appears in the output. To solve this, use a struct pointer instead :

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type Dog struct {
	Breed    string
	WeightKg int
	// Now `Size` is a pointer to a `dimension` instance
	Size *dimension `json:",omitempty"`
}
// prints {"Breed":"pug","WeightKg":0}