How to print the values of slices
ArraysGoArrays Problem Overview
I want to see the values which are in the slice. How can I print them?
projects []Project
Arrays Solutions
Solution 1 - Arrays
You can try the %v, %+v or %#v verbs of go fmt:
fmt.Printf("%v", projects)
If your array (or here slice) contains struct (like Project), you will see their details.
For more precision, you can use %#v to print the object using Go-syntax, as for a literal:
%v the value in a default format.
when printing structs, the plus flag (%+v) adds field names
%#v a Go-syntax representation of the value
For basic types, fmt.Println(projects) is enough.
Note: for a slice of pointers, that is []*Project (instead of []Project), you are better off defining a String() method in order to display exactly what you want to see (or you will see only pointer address).
See this play.golang example.
Solution 2 - Arrays
For a []string, you can use strings.Join():
s := []string{"foo", "bar", "baz"}
fmt.Println(strings.Join(s, ", "))
// output: foo, bar, baz
Solution 3 - Arrays
I prefer fmt.Printf("%+q", arr) which will print
["some" "values" "list"]
Solution 4 - Arrays
If you just want to see the values of an array without brackets, you can use a combination of fmt.Sprint() and strings.Trim()
a := []string{"a", "b"}
fmt.Print(strings.Trim(fmt.Sprint(a), "[]"))
fmt.Print(a)
Returns:
a b
[a b]
Be aware though that with this solution any leading brackets will be lost from the first value and any trailing brackets will be lost from the last value
a := []string{"[a]", "[b]"}
fmt.Print(strings.Trim(fmt.Sprint(a), "[]")
fmt.Print(a)
Returns:
a] [b
[[a] [b]]
For more info see the documentation for strings.Trim()
Solution 5 - Arrays
If you want to view the information in a slice in the same format that you'd use to type it in (something like ["one", "two", "three"]), here's a code example showing how to do that:
package main
import (
"fmt"
"strings"
)
func main() {
test := []string{"one", "two", "three"} // The slice of data
semiformat := fmt.Sprintf("%q\n", test) // Turn the slice into a string that looks like ["one" "two" "three"]
tokens := strings.Split(semiformat, " ") // Split this string by spaces
fmt.Printf(strings.Join(tokens, ", ")) // Join the Slice together (that was split by spaces) with commas
}
Solution 6 - Arrays
fmt.Printf() is fine, but sometimes I like to use pretty print package.
import "github.com/kr/pretty"
pretty.Print(...)
Solution 7 - Arrays
I wrote a package named Pretty Slice. You can use it to visualize slices, and their backing arrays, etc.
package main
import pretty "github.com/inancgumus/prettyslice"
func main() {
nums := []int{1, 9, 5, 6, 4, 8}
odds := nums[:3]
evens := nums[3:]
nums[1], nums[3] = 9, 6
pretty.Show("nums", nums)
pretty.Show("odds : nums[:3]", odds)
pretty.Show("evens: nums[3:]", evens)
}
This code is going produce and output like this one:
For more details, please read: https://github.com/inancgumus/prettyslice
Solution 8 - Arrays
You could use a for loop to print the []Project as shown in @VonC excellent answer.
package main
import "fmt"
type Project struct{ name string }
func main() {
projects := []Project{{"p1"}, {"p2"}}
for i := range projects {
p := projects[i]
fmt.Println(p.name) //p1, p2
}
}