sql - 戈朗 : Multiple SQL query generate extra empty {{range. }}

Question

In the application, I will use totally different query for the second query. The second query will be quite long SELECT SIMILARITY query. In this question, I give simple query to make it easier to understand

我需要在模板中打印来自 PostgreSQL 的数据。一切正常，但输出 HTML 有额外的 range。

下面是 HTML 输出。您可以看到没有值的额外 range:

<table>
    <tr>
        <th>Title</th>
        <th>Content</th>
    </tr>

    <tr>
        <td>Nation</td>
        <td>Nation has various meanings, and the meaning has changed over time</td>
    </tr>

    <tr>
        <td></td>
        <td></td>
    </tr>

</table>

<h1>ID number:</h1>

<h3></h3>

<h3>5</h3>

下面是server.go

package main

import (
    "database/sql"
    "github.com/labstack/echo"
    _ "github.com/lib/pq"
    "html/template"
    "io"
    "log"
    "net/http"
)

type Gallery struct {
    Title, Content, Idnumber string
}

type (
    Template struct {
        templates *template.Template
    }
)

func (t *Template) Render(w io.Writer, name string, data interface{}) *echo.HTTPError {
    if err := t.templates.ExecuteTemplate(w, name, data); err != nil {
        return &echo.HTTPError{Error: err}
    }
    return nil
}

func main() {
    e := echo.New()

    db, err := sql.Open("postgres", "user=postgres password=apassword dbname=lesson4 sslmode=disable")
    if err != nil {
        log.Fatal(err)
    }

    t := &Template{
        templates: template.Must(template.ParseFiles("public/views/testhere.html")),
    }
    e.Renderer(t)

    e.Get("/post/:uritext", func(c *echo.Context) *echo.HTTPError {

        rows, err := db.Query("SELECT title, content FROM gallery WHERE uri=$1", c.Param("uritext"))
        anotherquery, err := db.Query("SELECT id AS idnumber FROM gallery WHERE uri=$1", c.Param("uritext"))
        if err != nil {
            log.Fatal(err)
        }

        gallery := []Gallery{}

        for rows.Next() {
            g := Gallery{}
            err := rows.Scan(&g.Title, &g.Content)

            if err != nil {
                log.Fatal(err)
            }

            gallery = append(gallery, g)
        }

        for anotherquery.Next() {
            g := Gallery{}
            err := anotherquery.Scan(&g.Idnumber)

            if err != nil {
                log.Fatal(err)
            }

            gallery = append(gallery, g)
        }

        return c.Render(http.StatusOK, "onlytestingtpl", gallery)
    })

    e.Run(":4444")
}

下面是模板public/views/testhere.html

{{define "onlytestingtpl"}}
<table>
    <tr>
        <th>Title</th>
        <th>Content</th>
    </tr>
    {{range.}}
    <tr>
        <td>{{.Title}}</td>
        <td>{{.Content}}</td>
    </tr>
    {{end}}
</table>

<h1>ID number:</h1>
{{range.}}
<h3>{{.Idnumber}}</h3>
{{end}}

{{end}}

我对模板中的 range 有感觉，但我不知道，因为没有错误。

Answer 1

我觉得很合适。您正在运行两个单独的查询:

rows, err := db.Query("SELECT title, content FROM gallery WHERE uri=$1", c.Param("uritext"))
anotherquery, err := db.Query("SELECT id AS idnumber FROM gallery WHERE uri=$1", c.Param("uritext"))

然后从两者创建一个 slice :

gallery = append(gallery, g)
gallery = append(gallery, g)

所以你有两行:

{ "Nation", "Nation...", 0 }
{ "", "", 5 }

这是你想要的吗？如果您希望它们合并，您只需将查询更改为:

SELECT title, content, id as idnumber FROM gallery WHERE uri=$1

如果你想要两个单独的列表，那么也许你应该有两个单独的类型:

type Gallery struct {
    Title, Content string
}
type IDNumber string

构建两个单独的列表并使用组合对象进行渲染:

type Model struct {
    Galleries []Gallery
    IDNumbers []IDNumber
}
return c.Render(http.StatusOK, "onlytestingtpl", Model{
    Galleries: galleries,
    IDNumbers: idnumbers,
})

你的模板以:

结尾

{{range .Galleries}}
<tr>
    <td>{{.Title}}</td>
    <td>{{.Content}}</td>
</tr>
{{end}}