用golang打印可读变量

Question

如何以可读的方式打印地图,结构或其他内容？

使用PHP,你可以这样做

echo '<pre>';
print_r($var);
echo '</pre>';

要么

header('content-type: text/plain');
print_r($var);

Answer 1

使用Go fmt包.例如,

package main

import "fmt"

func main() {
    variable := "var"
    fmt.Println(variable)
    fmt.Printf("%#v\n", variable)
    header := map[string]string{"content-type": "text/plain"}
    fmt.Println(header)
    fmt.Printf("%#v\n", header)
}

输出:

var
"var"
map[content-type:text/plain]
map[string]string{"content-type":"text/plain"}

包fmt

import "fmt" 

概观

包fmt实现了格式化的I/O,其功能类似于C的printf和scanf.格式'动词'来自C,但更简单.

Answer 2

我认为在许多情况下，使用“％v”足够简洁：

fmt.Printf("%v", myVar)

在fmt软件包的文档页面中：

以默认格式％v值。打印结构时，加号（％+ v）添加字段名称

％＃v值 的Go语法表示形式

这是一个例子：

package main

import "fmt"

func main() {
    // Define a struct, slice and map
    type Employee struct {
        id   int
        name string
        age  int
    }
    var eSlice []Employee
    var eMap map[int]Employee

    e1 := Employee{1, "Alex", 20}
    e2 := Employee{2, "Jack", 30}
    fmt.Printf("%v\n", e1)
    // output: {1 Alex 20}
    fmt.Printf("%+v\n", e1)
    // output: {id:1 name:Alex age:20}
    fmt.Printf("%#v\n", e1)
    // output: main.Employee{id:1, name:"Alex", age:20}

    eSlice = append(eSlice, e1, e2)
    fmt.Printf("%v\n", eSlice)
    // output: [{1 Alex 20} {2 Jack 30}]
    fmt.Printf("%#v\n", eSlice)
    // output: []main.Employee{main.Employee{id:1, name:"Alex", age:20}, main.Employee{id:2, name:"Jack", age:30}}

    eMap = make(map[int]Employee)
    eMap[1] = e1
    eMap[2] = e2
    fmt.Printf("%v\n", eMap)
    // output: map[1:{1 Alex 20} 2:{2 Jack 30}]
    fmt.Printf("%#v\n", eMap)
    // output: map[int]main.Employee{1:main.Employee{id:1, name:"Alex", age:20}, 2:main.Employee{id:2, name:"Jack", age:30}}
}

Answer 3

您可以用来fmt.Println()打印。您将需要导入“fmt”包（参见下面的示例）。许多数据类型都可以直接打印。如果您想获得自定义类型的人类可读打印，您需要String() string为该类型定义一个方法。

要尝试以下示例，请单击此处：http ://play.golang.org/p/M6_KnRJ3Da

package main

import "fmt"

// No `String()` method
type UnstringablePerson struct {
    Age int
    Name string
}

// Has a `String()` method
type StringablePerson struct {
    Age int
    Name string
}

// Let's define a String() method for StringablePerson, so any instances
// of StringablePerson can be printed how we like
func (p *StringablePerson) String() string {
    return fmt.Sprintf("%s, age %d", p.Name, p.Age)
}

func main() {
    // Bobby's type is UnstringablePerson; there is no String() method
    // defined for this type, so his printout will not be very friendly
    bobby := &UnstringablePerson{
        Age: 10,
        Name: "Bobby",
    }

    // Ralph's type is StringablePerson; there *is* a String() method
    // defined for this type, so his printout *will* be very friendly
    ralph := &StringablePerson{
        Age: 12,
        Name: "Ralph",
    }
    fmt.Println(bobby) // prints: &{10 Bobby}
    fmt.Println(ralph) // prints: Ralph, age 12
}