book_store_gql

Prerequisite

• go-pg package: https://pg.uptrace.dev/
• gqlgen, the tool we are using to generate graphql server code: https://gqlgen.com/getting-started/

Init repo. We don't need to run it. Because we already ran it when we init this repo

go run github.com/99designs/gqlgen init

How to add your graphQL Model

Add model in file graph/book.graphql

extend type RootQuery {
    searchBooks(keyword: String!, pageCursor: PageCursor!): SearchBooksResponse
    generateBookPresignObject(id: String!):BookPresignObject
}

type SearchBooksResponse {
    pageInfo: PageInfo!
    books: [Book]
}

type BookPresignObject {
    presignedUrl: String!
}

type Book {
    id: ID!
    title: String!
    description: String!
    descriptionTrimmed: String!
    pages: Int!
    language: String!
    rating: Int!
    reviews: Int!
    authors: [Author]
    publishers: [Publisher]
    topics: [Topic]
    coverURL: String!
    url: String!
    issuedAt: Time!
    createdAt: Time!
    updatedAt: Time!
    type: String!
}

run command to generate code

go generate ./...

all generated fill will go to folder graph

all books resolvers will goto resolver/book.resolvers.go. You need to implement it yourself

for example:

func (r *rootQueryResolver) SearchBooks(ctx context.Context, keyword string, pageCursor model.PageCursor) (*model.SearchBooksResponse, error) {
    // do something here.
}

gqlgen will also create data model for you. If you want to customize it, cut the definition from model graph/model/models_gen.go and put it into graph/model/models_custom.go. For example:

// original model
package model

// ------------ in file model_gen.go
// original model
type Author struct {
	ID          string    `json:"id"`
	Name        string    `json:"name"`
	Nationality string    `json:"nationality"`
	Description string    `json:"description"`
	CreatedAt   time.Time `json:"createdAt"`
	UpdatedAt   time.Time `json:"updatedAt"`
	Books       []*Book   `json:"books"`
}

// ----------- in file model_custom.go
// modified model
type Author struct {
	ID          string    `json:"id"`
	Name        string    `json:"name"`
	Nationality string    `json:"nationality"`
	Description string    `json:"description"`
	CreatedAt   time.Time `json:"createdAt"`
	UpdatedAt   time.Time `json:"updatedAt"`

	// customized fields
	//Books       []*Book    `json:"books"`
	BookAuthor *BookAuthor `json:"-"`
}

you can also put modified model in other files, but should be under package model. for example, put it into auth.model.go

add dataloader

run following command to generate code

go run github.com/vektah/dataloaden AuthorLoader string "[]*github.com/liujun5885/book_store_gql/graph/model.Author"

it will generate the file authorloader_gen.go

put file authorloader_gen.go in folder graph/dataloader

In the future, if you want to generate any dataloader please also put into folder graph/dataloader

in file graph/dataloader/dataloader.go, it's the implementation of querying data from DB, for example:

package dataloader

func DataLoader(db *pg.DB, next http.Handler) http.Handler {
	return http.HandlerFunc(func(writer http.ResponseWriter, request *http.Request) {
		loaders := map[string]interface{}{
			// Put all dataloader in this mapping
			authorLoaderKey:    BuildAuthorLoader(db),
			publisherLoaderKey: BuildPublisherLoader(db),
		}
		ctx := request.Context()
		for k, v := range loaders {
			ctx = context.WithValue(ctx, k, v)
		}
		next.ServeHTTP(writer, request.WithContext(ctx))
	})
}

referring to

https://dev.to/glyphack/introduction-to-graphql-server-with-golang-1npk

99designs/gqlgen#785 (comment)

add sqitch for project

1. create folder in project

referring to: Sqitch Tutorial

mkdir -p sqitch/book_store_ugc

2. create user for project

CREATE USER book_store PASSWORD 'aaaaa';
CREATE DATABASE book_store_ugc;
CREATE DATABASE book_store_assets;
GRANT ALL on database book_store_ugc to book_store;
GRANT ALL on database book_store_assets to book_store;

3. init sqitch project

sqitch init book_store_ugc --uri  https://github.com/liujun5885/book_store_gql/ --engine pg

4. add sqitch target. I will use local pg for dev, so I created a local target.

sqitch target add local db:pg://book_store:aaaaa@localhost:5432/book_store_ugc

5. add local target to engine pg.

sqitch engine add pg --target local 

6. test it under folder sqitch/book_store_ugc

sqitch deploy
sqitch verify
sqitch revert