Only update non empty struct fields in golang

Question

Is there an easy way to only update non-nil/empty fields in go(-lang)?

Given these two structs:

type UserAccount struct {
    Id         string `json:"id" binding:"required"`
    Enrolled   bool   `json:"enrolled" binding:"required"`
    Email      string `json:"email" binding:"required"`
    GivenName  string `json:"given_name" binding:"required"`
    FamilyName string `json:"family_name" binding:"required"`
    PictureURL string `json:"picture" binding:"required"`
    Nickname   string `json:"nickname" binding:"required"`
}
type ProfilePayload struct {
    Email      string `json:"email,omitempty"`
    GivenName  string `json:"given_name,omitempty"`
    FamilyName string `json:"family_name,omitempty"`
    PictureURL string `json:"picture,omitempty"`
    Nickname   string `json:"nickname,omitempty"` 
}

Is it possible to only update non-nil fields in an UserAccount struct. For example, all fields except Email are nil/empty in a ProfilePayload, is there an easy way to "merge" them together and only set the Email field in a UserAccount to a new value and keeping everything else in the UserAccount the same?

if payload.Email != "" {
    account.Email = payload.Email
}
....

Isn´t really an option for me.

Because I want to do it with quite large structs and there has to be a better solution. — Eric Meier
– Eric Meier, Commented Apr 6, 2018 at 22:27
The only way to do it without explicitly checking every field is with reflection. See golang.org/pkg/reflect. — Andy Schweig
– Andy Schweig, Commented Apr 7, 2018 at 21:17

John Balvin Arias · Accepted Answer · 2018-04-09 08:59:27Z

2

What if you just restructured your code

type ProfilePayload struct {
    Email      string `json:"email,omitempty"`
    GivenName  string `json:"given_name,omitempty"`
    FamilyName string `json:"family_name,omitempty"`
    PictureURL string `json:"picture,omitempty"`
    Nickname   string `json:"nickname,omitempty"` 
}
type UserAccount struct {
    Id         string `json:"id" binding:"required"`
    Enrolled   bool   `json:"enrolled" binding:"required"`
    ProfilePayload //now it has all the fields from ProfilePayload
}

When decoding to json you just decode it to UserAccount, and then you can extract ProfilePayload from UserAccount if you want

answered Apr 9, 2018 at 8:59

John Balvin Arias

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