Gin Validation for optional pointer to be uuid?

Question

I have this struct

// CreateAccount Create Account Data Args
type CreateAccount struct {
    ....
    RegistrationID string  `example:"2c45e4ec-26e0-4043-86e4-c15b9cf985a2" json:"registration_id" binding:"max=63"`
    ParentID       *string `example:"7c45e4ec-26e0-4043-86e4-c15b9cf985a7" json:"parent_id" format:"uuid"`
}

ParentID is a pointer, and it is optional. But if it is provided, it should be uuid.

var params helper.CreateAccount
if err := ctx.ShouldBindJSON(&params); err != nil {
...
}

if add this to ParentID binding:"uuid", it makes ParentID a required filed! Which is not the case here. If and only if ParentID is given, it should be uuid. Is there anyway to set it up this way.

Answer 1

You have to place the omitempty tag first.

type CreateAccount struct {
    ....
    RegistrationID string  `json:"registration_id" binding:"max=63"`
    ParentID       *string `json:"parent_id" binding:"omitempty,uuid"`
}

From the validator docs:

Allows conditional validation, for example if a field is not set with a value (Determined by the "required" validator) then other validation such as min or max won't run

The way I read this sentence is that omitempty has to be placed before others, so that it can stop the validator chain if the value is not equal to the zero value.