spew--极其好用的Go语言深层打印包

留言

深度打印


如果变量为接口/多层嵌套的复杂结构体,且里面包含指针类型,用fmt打印时,结果将十分不可读. go-spew这个package,非常完美地解决了此问题.

spew为动词,译作"(使) 喷出，涌出",也有"呕吐"的意思.读作"si biu".

[例句]The volcano spewed out more scorching volcanic ashes, gases and rocks
火山喷出更多灼热的火山灰、气体和岩块。

 
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package main

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

type AppDeveloper struct {
	DeveloperID string   `json:"id"`
	Name        *string  `json:"name"`
	Email       string   `json:"email"`
	CompanyInfo *company `json:"company"`
}

type company struct {
	companyName  string
	companyOwner *string
	address      string
	isListed     *bool
}

func main() {

	name := "Alex"
	entrepreneur := "马化腾" //企业家,创业者
	isPubliced := true    //香港和英国：a public company; 美国：a listed company

	user := AppDeveloper{
		"123",
		&name, "i@dashen.tech",
		&company{
			"腾讯",
			&entrepreneur,
			"深圳",
			&isPubliced},
	}

	fmt.Println(user)

	n, err := spew.Println(user)

	fmt.Println(n, err)

}

输出为:

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{123 0xc0000102d0 i@dashen.tech 0xc000066390}

{123 <*>Alex i@dashen.tech <*>{腾讯 <*>马化腾 深圳 <*>true}}

68 <nil>


// Println is a wrapper for fmt.Println that treats each argument as if it were
passed with a default Formatter interface returned by NewFormatter. It
returns the number of bytes written and any write error encountered. See
NewFormatter for formatting details.

spew.Println() 返回写入的字节数以及遇到的任何写入错误

可见,如果遇到pointer类型,会在前面标出为<*>类型,但输出的还是该指针在内存里存放的值;

和fmt相比,可读性强太多了

spew包中其他的方法


spew.Dump:
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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() {

	commit := "第一次提交"
	o := Project{Name: "hello", Title: "world", Commits: &commit}
	spew.Dump(o)
}

输出为:

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(main.Project) {
 Id: (int64) 0,
 Title: (string) (len=5) "world",
 Name: (string) (len=5) "hello",
 Data: (*string)(<nil>),
 Commits: (*string)(0xc0000682b0)((len=15) "第一次提交")
}

spew.Printf:
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package main

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

func main() {

	ui8 := uint8(5)
	pui8 := &ui8
	ppui8 := &pui8

	// Create a circular data type.
	type circular struct {
		ui8 uint8
		c   *circular
	}
	c := circular{ui8: 1}
	c.c = &c

	fmt.Println("pui8:", pui8)
	fmt.Println("pui8:", *pui8)
	fmt.Println("------------")
	fmt.Println("ppui8:", ppui8)
	fmt.Println("ppui8:", **ppui8)

	fmt.Println("------------")

	// Print!
	spew.Printf("ppui8: %v\n", ppui8)
	spew.Printf("circular: %v\n", c)
}


输出为:

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pui8: 0xc00008e160
pui8: 5
------------
ppui8: 0xc000088030
ppui8: 5
------------
ppui8: <**>5
circular: {1 <*>{1 <*><shown>}}

spew.ConfigState:
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package main

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

func main() {

	scs := spew.ConfigState{Indent: "\t"}

	// Output using the ConfigState instance.
	v := map[string]int{"one": 1}

	scs.Printf("v: %v\n", v)

	fmt.Println("--------------------")

	scs.Dump(v)
}

输出为:

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v: map[one:1]
--------------------
(map[string]int) (len=1) {
        (string) (len=3) "one": (int) 1
}

// Indent specifies the string to use for each indentation level. The
global config instance that all top-level functions use set this to a
single space by default. If you would like more indentation, you might
set this to a tab with “\t” or perhaps two spaces with “ “.

//缩进指定用于每个缩进级别的字符串。 默认情况下，所有顶级功能使用的全局配置实例将其设置为单个空间。 如果您希望缩进更多，可以将其设置为带有“ \ t”的选项卡，或者带有“”的两个空格。



番外: *符号有两个用处:

  1. 表明这是一个指针类型,是一个状态,形容词;
  2. 解引用,是一个动作,动词

如 上面代码中的Name字段的类型为*string,即要求该字段需要是字符串指针类型.

变量name为string类型,则取指针即&name后即变为*string类型,对&name解引用*&name则又变为string类型

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package main

import "fmt"

func main() {
	name := "fliter"
	fmt.Println(*&name)

}

输出为:

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fliter

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