如何在控制台中打印struct变量？

本文翻译自：How to print struct variables in console?

How can I print (in the console) the Id , Title , Name , etc. of this struct in Golang? 如何在Golang中打印（在控制台中）此结构的Id ， Title ， Name等？

type Project struct {
    Id int64 `json:"project_id"`
    Title string `json:"title"`
    Name string `json:"name"`
    Data Data `json:"data"`
    Commits Commits `json:"commits"`
}

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#1楼

参考：https://stackoom.com/question/1eqie/如何在控制台中打印struct变量

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#2楼

To print the name of the fields in a struct: 要在结构中打印字段的名称：

fmt.Printf("%+v\n", yourProject)

From the fmt package : 来自fmt包 ：

when printing structs, the plus flag ( %+v ) adds field names 打印结构时，加号标志（ %+v ）添加字段名称

That supposes you have an instance of Project (in ' yourProject ') 假设您有一个Project实例（在' yourProject '中）

The article JSON and Go will give more details on how to retrieve the values from a JSON struct. 文章JSON和Go将提供有关如何从JSON结构中检索值的更多详细信息。

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This Go by example page provides another technique: 这个Go by example页面提供了另一种技术：

type Response2 struct {
  Page   int      `json:"page"`
  Fruits []string `json:"fruits"`
}

res2D := &Response2{
    Page:   1,
    Fruits: []string{"apple", "peach", "pear"}}
res2B, _ := json.Marshal(res2D)
fmt.Println(string(res2B))

That would print: 那将打印：

{"page":1,"fruits":["apple","peach","pear"]}

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If you don't have any instance, then you need to use reflection to display the name of the field of a given struct, as in this example . 如果您没有任何实例，则需要使用反射来显示给定结构的字段名称， 如本例所示 。

type T struct {
    A int
    B string
}

t := T{23, "skidoo"}
s := reflect.ValueOf(&t).Elem()
typeOfT := s.Type()

for i := 0; i < s.NumField(); i++ {
    f := s.Field(i)
    fmt.Printf("%d: %s %s = %v\n", i,
        typeOfT.Field(i).Name, f.Type(), f.Interface())
}

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#3楼

I want to recommend go-spew , which according to their github "Implements a deep pretty printer for Go data structures to aid in debugging" 我想推荐go-spew ，根据他们的github“为Go数据结构实现深度漂亮的打印机以帮助调试”

go get -u github.com/davecgh/go-spew/spew

usage example: 用法示例：

package main

import (
    "github.com/davecgh/go-spew/spew"
)

type Project struct {
    Id      int64  `json:"project_id"`
    Title   string `json:"title"`
    Name    string `json:"name"`
    Data    string `json:"data"`
    Commits string `json:"commits"`
}

func main() {

    o := Project{Name: "hello", Title: "world"}
    spew.Dump(o)
}

output: 输出：

(main.Project) {
 Id: (int64) 0,
 Title: (string) (len=5) "world",
 Name: (string) (len=5) "hello",
 Data: (string) "",
 Commits: (string) ""
}

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#4楼

There's also go-render , which handles pointer recursion and lots of key sorting for string and int maps. 还有go-render ，它处理指针递归和字符串和int映射的大量键排序。

Installation: 安装：

go get github.com/luci/go-render/render

Example: 例：

type customType int
type testStruct struct {
        S string
        V *map[string]int
        I interface{}
}

a := testStruct{
        S: "hello",
        V: &map[string]int{"foo": 0, "bar": 1},
        I: customType(42),
}

fmt.Println("Render test:")
fmt.Printf("fmt.Printf:    %#v\n", a)))
fmt.Printf("render.Render: %s\n", Render(a))

Which prints: 哪个印刷品：

fmt.Printf:    render.testStruct{S:"hello", V:(*map[string]int)(0x600dd065), I:42}
render.Render: render.testStruct{S:"hello", V:(*map[string]int){"bar":1, "foo":0}, I:render.customType(42)}

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#5楼

Visit here to see the complete code. 访问此处查看完整代码。 Here you will also find a link for an online terminal where the complete code can be run and the program represents how to extract structure's information(field's name their type & value). 在这里，您还可以找到在线终端的链接，其中可以运行完整的代码，程序代表如何提取结构的信息（字段名称的类型和值）。 Below is the program snippet that only prints the field names. 以下是仅打印字段名称的程序片段。

package main

import "fmt"
import "reflect"

func main() {
    type Book struct {
        Id    int
        Name  string
        Title string
    }

    book := Book{1, "Let us C", "Enjoy programming with practice"}
    e := reflect.ValueOf(&book).Elem()

    for i := 0; i < e.NumField(); i++ {
        fieldName := e.Type().Field(i).Name
        fmt.Printf("%v\n", fieldName)
    }
}

/*
Id
Name
Title
*/

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#6楼

I think it would be better to implement a custom stringer if you want some kind of formatted output of a struct 我认为如果你想要某种struct的格式化输出，那么实现自定义stringer会更好

for example 例如

package main

    import "fmt"

    type Project struct {
        Id int64 `json:"project_id"`
        Title string `json:"title"`
        Name string `json:"name"`
    }

    func (p Project) String() string {
        return fmt.Sprintf("{Id:%d, Title:%s, Name:%s}", p.Id, p.Title, p.Name)
    }

    func main() {
        o := Project{Id: 4, Name: "hello", Title: "world"}
        fmt.Printf("%+v\n", o)
    }