Golang: Validate Struct Fields in Slice Items

I'm new to Golang.

golang version: 1.17.8

validator: "github.com/go-playground/validator/v10"

I want to validate an incoming JSON payload after loaded into nested struct data structure.
Here's my incoming JSON payload,

  {
  "name": "Yomiko",
  "address": {
    "city": "Tokyo",
    "street": "Shibaura St"
  },
  "children":[
    {
      "lastName": "Takayashi"
    }
  ],
  "isEmployed": false
  }

Here's my user.go file,

package main

type User struct {
	Name    string
	Address *Address `validate:"required"`
	Children []*Child
	IsEmployed *bool `validate:"required"`
}
type Address struct {
	City     string `validate:"required"`
	Street  string `validate:"required"`
}

type Child struct {
	Title string `validate:"required"`
	FirstName string
	LastName string `validate:"required"`
}

Here's my test function,

func TestUserPayload(t *testing.T) {
	actualUserPayload := NewUserPayloadFromFile("userpayload.json")

	validate := validator.New()
	err := validate.Struct(actualUserPayload)
	if err != nil {
		t.Error("Validation Error: ", err)
	}

}

This test passes. However, I expected it to fail as Child.Title is marked as required. I expected the following error,

Validation Error:  Key: 'Child.Title' Error:Field validation for 'Title' failed on the 'required' tag

However, when I loop through the children slice and validate each child struct as follows the test fails as expected,

func TestUserPayload(t *testing.T) {
	actualUserPayload := NewUserPayloadFromFile("userpayload.json")

	validate := validator.New()
	err := validate.Struct(actualUserPayload)
	if err != nil {
		t.Error("Validation Error: ", err)
	}

	children := actualUserPayload.Children

	for _, child := range children {
		err := validate.Struct(child)
		if err != nil {
			t.Error("Validation Error: ", err)
		}
	}

}

Is there a straightforward way to do this validation of the items in a slice of structs?

According to the documentation of the validator package, you can use dive in your struct tag to get this behavior. This causes the validator to also validate the nested struct/slice/etc.

So you would need to update your User struct to this:

type User struct {
	Name       string
	Address    *Address `validate:"required"`
	Children   []*Child `validate:"dive"`
	IsEmployed *bool    `validate:"required"`
}

Here it is working in Go Playground

I'm using Gin, binding:required,dive works for me:

type Child struct {
  Name string `json:"name" binding:"required"`
}

type Body struct {
  Children []Child `json:"children" binding:"required,dive"` 👈
}