填充包含切片的结构

Question

我正在尝试收集 Go 的基础知识。

我正在尝试在 golang 中使用结构的预填充值呈现模板。但没有运气

func ServeIndex(w http.ResponseWriter, r *http.Request) {
    p := &Page{
        Title:   " Go Project CMS",
        Content: "Welcome to our home page",
        Posts: []*Post{
            &Post{
                Title:         "Hello World",
                Content:       "Hello, World Thanks for coming to this site",
                DatePublished: time.Now(),
            },
            &Post{
                Title:         "A Post with comments",
                Content:       "Here is the controversial post",
                DatePublished: time.Now(),
                Comments: []*Comment{
                    &Comment{
                        Author:        "Sathish",
                        Comment:       "Nevermind, I guess",
                        DatePublished: time.Now().Add(-time.Hour / 2),
                    },
                },
            },
        },
    }

    Tmpl.ExecuteTemplate(w, "page", p)
}

这是我的结构定义

import (
    "html/template"
    "time"
)

// Tmpl is exported and can be used by other packages
var Tmpl = template.Must(template.ParseGlob("../templates/*"))

type Page struct {
    Title   string
    Content string
    Posts   *[]Post
}

type Post struct {
    Title         string
    Content       string
    DatePublished time.Time
    Comments      *[]Comment
}

type Comment struct {
    Author        string
    Comment       string
    DatePublished time.Time
}

当我尝试通过 main.go 文件运行此代码时，我收到以下错误

../handler.go:60: cannot use []*Comment literal (type []*Comment) as type *[]Comment in field value
../handler.go:62: cannot use []*Post literal (type []*Post) as type *[]Post in field value

你能帮我理解真正的问题是什么吗？我正在关注视频教程。

编辑：根据 mktopriva 建议更新代码

func ServeIndex(w http.ResponseWriter, r *http.Request) {
    p := &Page{
        Title:   " Go Project CMS",
        Content: "Welcome to our home page",
        Posts: *[]Post{
            &Post{
                Title:         "Hello World",
                Content:       "Hello, World Thanks for coming to this site",
                DatePublished: time.Now(),
            },
            &Post{
                Title:         "A Post with comments",
                Content:       "Here is the controversial post",
                DatePublished: time.Now(),
                Comments: *[]Comment{
                    &Comment{
                        Author:        "Sathish",
                        Comment:       "Nevermind, I guess",
                        DatePublished: time.Now().Add(-time.Hour / 2),
                    },
                },
            },
        },
    }

    Tmpl.ExecuteTemplate(w, "page", p)
}

遇到以下错误

../handler.go:45: cannot use Post literal (type *Post) as type Post in array or slice literal
../handler.go:50: cannot use *Post literal (type *Post) as type Post in array or slice literal
../handler.go:55: cannot use Comment literal (type *Comment) as type Comment in array or slice literal
../handler.go:60: invalid indirect of []Comment literal (type []Comment)
../handler.go:62: invalid indirect of []Post literal (type []Post)

Answer 1

@mkopriva 是正确的，但我猜这不是你想要的......

您的结构声明稍有偏差，例如，Page 有a pointer to a slice of Post values，您可能想要a slice of Post pointers，因为这通常是人们使用切片的方式。你的声明只需要在类型旁边加上*，而不是[]，然后你的创建代码就可以工作了。

import (
    "html/template"
    "time"
)

// Tmpl is exported and can be used by other packages
var Tmpl = template.Must(template.ParseGlob("../templates/*"))

type Page struct {
    Title   string
    Content string
    Posts   []*Post
}

type Post struct {
    Title         string
    Content       string
    DatePublished time.Time
    Comments      []*Comment
}

type Comment struct {
    Author        string
    Comment       string
    DatePublished time.Time
}

Answer 2

您将某些字段类型声明为 pointers-to-slices，但您向它们提供了 slice-of-pointers 类型的值。

例如，给定字段Comments *[]Comment，您可以像这样初始化它的值：

Comments: &[]Comment{},

查看此处了解更多替代方案：https://play.golang.org/p/l9HQEGxE5MP

---

同样在切片、数组和映射中，如果元素类型已知，即它不是接口，则可以在元素的初始化中省略类型，而只使用花括号，因此代码如下：

[]*Post{&Post{ ... }, &Post{ ... }}

可以改为：

[]*Post{{ ... }, { ... }}