graphql學習(三)

GraphQL中有三種操作類型，分别是query、mutation、subscription:

• query: 擷取資料,對應CRUD裡的R;
• mutation: 操作資料,對應CRUD裡的CUD(建立,更新,删除);
• subscription: 消息訂閱,資料更改時進行消息推送.

之前已經學習了query, 這一篇重點學習mutation.

首先,修改models/article.go檔案,增加相應的CUD函數:

// Create a new article with the title and content provided
func CreateNewArticle(title, content string) (*Article, error) {
    // Set the ID of a new article to one more than the number of articles
    a := Article{ID: len(articleList) + 1, Title: title, Content: content}

    // Add the article to the list of articles
    articleList = append(articleList, a)

    return &a, nil
}

// Update a article
func UpdateArticle(id int, title, content string) (*Article, error) {
    a, err := GetArticleByID(id)
    if err != nil {
        return nil, err
    }

    if title != "" {
        a.Title = title
    }
    if content != "" {
        a.Content = content
    }

    return a, nil
}

// Delete a article
func DeleteArticle(id int) error {
    for k, a := range articleList {
        if a.ID == id {
            articleList = append(articleList[:k], articleList[k+1:]...)
            return nil
        }
    }
    return errors.New("Article not found")
}           

然後是修改schema/article.go,增加相應的mutation:

// 定義mutation,增删改操作
// add
var addArticle = graphql.Field{
    Name:        "新文章",
    Description: "增加新文章",
    Type:        articleType,
    Args: graphql.FieldConfigArgument{
        "title": &graphql.ArgumentConfig{
            Type: graphql.String,
        },
        "content": &graphql.ArgumentConfig{
            Type: graphql.String,
        },
    },
    Resolve: func(p graphql.ResolveParams) (result interface{}, err error) {
        title, _ := p.Args["title"].(string)
        content, _ := p.Args["content"].(string)

        result, err = models.CreateNewArticle(title, content)
        if err != nil {
            return nil, err
        }

        return result, nil
    },
}

// update
var updateArticle = graphql.Field{
    Name:        "編輯文章",
    Description: "編輯文章",
    Type:        articleType,
    Args: graphql.FieldConfigArgument{
        "id": &graphql.ArgumentConfig{
            Type: graphql.Int,
        },
        "title": &graphql.ArgumentConfig{
            Type: graphql.String,
        },
        "content": &graphql.ArgumentConfig{
            Type: graphql.String,
        },
    },
    Resolve: func(p graphql.ResolveParams) (result interface{}, err error) {
        id, _ := p.Args["id"].(int)
        title, _ := p.Args["title"].(string)
        content, _ := p.Args["content"].(string)

        result, err = models.UpdateArticle(id, title, content)
        if err != nil {
            return nil, err
        }

        return result, nil
    },
}

// delete
var deleteArticle = graphql.Field{
    Name:        "删除文章",
    Description: "删除指定Id的文章",
    Type:        articleType,
    Args: graphql.FieldConfigArgument{
        "id": &graphql.ArgumentConfig{
            Type: graphql.Int,
        },
    },
    Resolve: func(p graphql.ResolveParams) (result interface{}, err error) {
        id, _ := p.Args["id"].(int)

        // 查找文章是否存在
        result, err = models.GetArticleByID(id)
        if err != nil {
            return nil, err
        }

        if err = models.DeleteArticle(id); err != nil {
            return nil, err
        }

        return result, nil
    },
}

// 定義增删改方法
var mutationType = graphql.NewObject(graphql.ObjectConfig{
    Name:        "mutation",
    Description: "增删改",
    Fields: graphql.Fields{
        "add":    &addArticle,
        "update": &updateArticle,
        "delete": &deleteArticle,
    },
})

// 定義Schema用于http handler處理
var Schema, _ = graphql.NewSchema(graphql.SchemaConfig{
    Query:    rootQuery,
    Mutation: mutationType,   // 這裡不能是nil了,對應前面的定義
})           

測試結果話不多說,上圖:

新增文章:

編輯文章

删除文章

代碼在github上的連結

傳送門