Mutations

What Is A Mutation

Simply mutations are just like queries but they can cause a data write, Technically Queries can be used to write data too however it’s not suggested to use it. So mutations are like queries, they have names, parameters and they can return data.

A Simple Mutation

Let’s try to implement the createLink mutation, since we do not have a database set up yet(we’ll get it done in the next section) we just receive the link data and construct a link object and send it back for response!

Open schema.resolvers.go and Look at CreateLink function:

func (r *mutationResolver) CreateLink(ctx context.Context, input model.NewLink) (*model.Link, error) {

This function receives a NewLink with type of input we defined NewLink structure in our schema.graphqls.

func (r *mutationResolver) CreateLink(ctx context.Context, input model.NewLink) (*model.Link, error) {
	var link model.Link
	var user model.User
	link.Address = input.Address
	link.Title = input.Title
	user.Name = "test"
	link.User = &user
	return &link, nil
}

now run server and use the mutation to create a new link:

mutation {
  createLink(input: {title: "new link", address:"http://address.org"}){
    title,
    user{
      name
    }
    address
  }
}

and you will get:

{
  "data": {
    "createLink": {
      "title": "new link",
      "user": {
        "name": "test"
      },
      "address": "http://address.org"
    }
  }
}

Nice now we know what are mutations and queries we can setup our database and make these implementations more practical.