What is the correct way to conditionally assign multiple properties to a struct-Golang-php.cn

What is the correct way to conditionally assign multiple properties to a struct

WBOY

Release： 2024-02-06 08:05:11

forward

665 people have browsed it

What is the correct way to conditionally assign multiple properties to a struct

Question content

I am developing a parser function for be's graphql query that I wrote in go. In the parser, I have user data that I want to update, using an input value that contains multiple possible update properties.

In javascript this can be done quickly via destructuring (pseudo):

const mergedobj = {...oldprops, ...newprops}

Currently, my parser function looks like this (using gqlgen as the graphql go parser):

func (r *mutationResolver) ModifyUser(ctx context.Context, input *model.ModifyUserInput) (*model.User, error) {
    id := input.ID
    us, ok := r.Resolver.UserStore[id]
    if !ok {
        return nil, fmt.Errorf("not found")
    }

    if input.FirstName != nil {
        us.FirstName = *input.FirstName
    }

    if input.LastName != nil {
        us.LastName = *input.LastName
    }

    if input.ProfileImage != nil {
        us.ProfileImage = input.ProfileImage
    }

    if input.Password != nil {
        us.Password = *input.Password
    }

    if input.Email != nil {
        us.Email = *input.Email
    }

    if input.InTomorrow != nil {
        us.InTomorrow = input.InTomorrow
    }

    if input.DefaultDaysIn != nil {
        us.DefaultDaysIn = input.DefaultDaysIn
    }

    r.Resolver.UserStore[id] = us

    return &us, nil
}

Copy after login

This feels very simple. Does it make sense to iterate over the struct keys in this case? Or is there another pattern I'm missing?

Correct answer

Use functions to reduce boilerplate:

func mergef[t any](a, b *t) {
    if b != nil {
        *a = *b
    }
}

...
mergef(&us.firstname, input.firstname)
mergef(&us.lastname, input.lastname)
...

Copy after login

Use the reflection package to reduce more boilerplate:

// merge sets fields in struct pointed to by d to 
// dereferenced fields in struct pointed to by s. 
//
// argument s must point to a struct with pointer type
// fields.   
// argument d must point to a struct with fields that 
// correspond to the fields in s: there must be a field
// in d with the same name as a field in s; the type of
// the field in s must be a pointer to the type of the field
// in d.   
func merge(d, s any) {
    sv := reflect.valueof(s).elem()
    dv := reflect.valueof(d).elem()
    for i := 0; i < sv.numfield(); i++ {
        sf := sv.field(i)
        if sf.isnil() {
            continue
        }
        df := dv.fieldbyname(sv.type().field(i).name)
        df.set(sf.elem())
    }
}

Copy after login

Use a function like this:

merge(us, input)

Copy after login

The above is the detailed content of What is the correct way to conditionally assign multiple properties to a struct. For more information, please follow other related articles on the PHP Chinese website!