structgo

How to print struct variables in console?


How can I print (to the console) the Id, Title, Name, etc. of this struct in Golang?

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

Solution

  • To print the name of the fields in a struct:

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

    From the fmt package:

    when printing structs, the plus flag (%+v) adds field names

    That supposes you have an instance of Project (in 'yourProject')

    The article JSON and Go will give more details on how to retrieve the values from a JSON struct.


    This Go by example page provides another technique:

    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:

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

    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.

    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())
    }