Use Go lang with Gin to return an empty array instead of null for JSON responses

Question

Use Go lang with Gin to return an empty array instead of null for JSON responses

I have a struct:

type ProductConstructed struct {
    Name string `json:"Name"`
    BrandMedals []string `json:"BRAND_MEDALS"`
}

When I use gin to return my object:

func  constructProduct(c *gin.Context) {
    var response ProductConstructed 
    response.Name = "toto"

    c.JSON(200, response)
}

func main() {
    var err error
    if err != nil {
        panic(err)
    }
    //gin.SetMode(gin.ReleaseMode)
    r := gin.Default()
    r.POST("/constructProductGo/v1/constructProduct", constructProduct)
    r.Run(":8200") // listen and serve on 0.0.0.0:8080
}

The output is:

null

But it should be:

[]

How can I make it return an empty array?

json go go-gin

Answer 1

Answer №1

After much deliberation, the decision was made to start by setting it up this way:

productCreated.BrandMedals = make([]string, 0)

Answer 2

After much deliberation, the decision was made to start by setting it up this way:

productCreated.BrandMedals = make([]string, 0)

Answer 3

Answer №2

To provide a clear explanation of why the solution above is effective:

slice1 has been declared but not defined, meaning no value has been assigned to it yet, resulting in it being equal to nil. When serialized, this will return as null.

slice2, on the other hand, has been both declared and defined. It is set to an empty slice rather than nil. After serialization, it will display as [].

var slice1 []string  // nil slice
slice2 := []string{} // zero-length but non-nil

json1, _ := json.Marshal(slice1)
json2, _ := json.Marshal(slice2)

fmt.Printf("%s\n", json1) // null
fmt.Printf("%s\n", json2) // []

fmt.Println(slice1 == nil) // true
fmt.Println(slice2 == nil) // false

Test it out on Go playground: https://play.golang.org/p/abc123xyz

For more information, visit: https://github.com/golang/go/wiki/CodeReviewComments#declaring-empty-slices

Answer 4

To provide a clear explanation of why the solution above is effective:

slice1 has been declared but not defined, meaning no value has been assigned to it yet, resulting in it being equal to nil. When serialized, this will return as null.

slice2, on the other hand, has been both declared and defined. It is set to an empty slice rather than nil. After serialization, it will display as [].

var slice1 []string  // nil slice
slice2 := []string{} // zero-length but non-nil

json1, _ := json.Marshal(slice1)
json2, _ := json.Marshal(slice2)

fmt.Printf("%s\n", json1) // null
fmt.Printf("%s\n", json2) // []

fmt.Println(slice1 == nil) // true
fmt.Println(slice2 == nil) // false

Test it out on Go playground: https://play.golang.org/p/abc123xyz

For more information, visit: https://github.com/golang/go/wiki/CodeReviewComments#declaring-empty-slices

Use Go lang with Gin to return an empty array instead of null for JSON responses

Answer №1

Answer №2

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