print readable variables with golang

Question

How to print a map, struct or whatever in a readable way?

With PHP you can to this

echo \'
\';
print_r($var);
echo \'
\';
         


        

Answer 1

You can use fmt.Println() to print. You will need to import the "fmt" package (see the example below). Many data types can be printed out of the box. If you want to get a human-readable print for custom types, you'll need to define a String() string method for that type.

To try the following example, click here: 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
}