callbacks.go
func UniqueFieldValidator(field string, zero interface{}, filters ...string) *Callback {
	return C("fire/UniqueFieldValidator", Only(Create, Update), func(ctx *Context) error {
		// check if field has changed
		if ctx.Operation == Update {
			// get original model
			original, err := ctx.Original()
			if err != nil {
				return err
			}

			// return if field has not been changed
			if reflect.DeepEqual(ctx.Model.MustGet(field), original.MustGet(field)) {
				return nil
			}
		}

		// get value
		value := ctx.Model.MustGet(field)

		// return if value is the zero value
		if value != NoZero && reflect.DeepEqual(value, zero) {
			return nil
		}

		// prepare query
		query := bson.M{
			coal.F(ctx.Model, field): value,
		}

		// add filters
		for _, field := range filters {
			query[coal.F(ctx.Model, field)] = ctx.Model.MustGet(field)
		}

		// exclude soft deleted documents if supported
		if sdm := coal.L(ctx.Model, "fire-soft-delete", false); sdm != "" {
			query[coal.F(ctx.Model, sdm)] = nil
		}

		// count
		ctx.Tracer.Push("mgo/Query.Count")
		ctx.Tracer.Tag("query", query)
		n, err := ctx.Store.C(ctx.Model).Find(query).Limit(1).Count()
		if err != nil {
			return err
		} else if n != 0 {
			return E("attribute %s is not unique", field)
		}
		ctx.Tracer.Pop()

		return nil
	})
}
func UniqueFieldValidator(field string, zero interface{}, filters ...string) *Callback {
	return C("fire/UniqueFieldValidator", Only(Create, Update), func(ctx *Context) error {
		// check if field has changed
		if ctx.Operation == Update {
			// get original model
			original, err := ctx.Original()
			if err != nil {
				return err
			}

			// return if field has not been changed
			if reflect.DeepEqual(ctx.Model.MustGet(field), original.MustGet(field)) {
				return nil
			}
		}

		// get value
		value := ctx.Model.MustGet(field)

		// return if value is the zero value
		if value != NoZero && reflect.DeepEqual(value, zero) {
			return nil
		}

		// prepare query
		query := bson.M{
			coal.F(ctx.Model, field): value,
		}

		// add filters
		for _, field := range filters {
			query[coal.F(ctx.Model, field)] = ctx.Model.MustGet(field)
		}

		// exclude soft deleted documents if supported
		if sdm := coal.L(ctx.Model, "fire-soft-delete", false); sdm != "" {
			query[coal.F(ctx.Model, sdm)] = nil
		}

		// count
		ctx.Tracer.Push("mgo/Query.Count")
		ctx.Tracer.Tag("query", query)
		n, err := ctx.Store.C(ctx.Model).Find(query).Limit(1).Count()
		if err != nil {
			return err
		} else if n != 0 {
			return E("attribute %s is not unique", field)
		}
		ctx.Tracer.Pop()

		return nil
	})
}
// UniqueFieldValidator ensures that the specified field of the current model will
// remain unique among the specified filters. If the value matches the provided
// zero value the check is skipped.
//
//	fire.UniqueFieldValidator("Name", "", "Creator")
//
// The special NoZero value can be provided to skip the zero check.
//
// The callback supports models that use the soft delete mechanism.