How to print struct variables in console

Question

How can I print  in 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

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When you have more complex structures  you might need to convert to JSON before printing      Convert structs to JSON  data  err    json Marshal myComplexStruct  fmt Printf   s n   data    Source  https   gist github com tetsuok 4942960

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Most of these packages are relying on the reflect package to make such things possible      fmt Sprintf   is using -  func  p  pp  printArg arg interface    verb rune  of standard lib  Go to line 638 -  https   golang org src fmt print go  Reflection   https   golang org pkg reflect   Example code   https   github com donutloop toolkit blob master debugutil prettysprint go

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Visit here to see the complete code  Here you will also find a link for an online terminal where the complete code can be run and the program represents how to extract structure s information field s name their type  amp  value   Below is the program snippet that only prints the field names   package main  import  fmt  import  reflect   func main         type Book struct           Id    int         Name  string         Title string            book    Book 1   Let us C    Enjoy programming with practice       e    reflect ValueOf  amp book  Elem        for i    0  i  lt  e NumField    i             fieldName    e Type   Field i  Name         fmt Printf   v n   fieldName              Id Name Title

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I think it would be better to implement a custom stringer if you want some kind of formatted output of a struct for example package main      import  quot fmt quot       type Project struct           Id int64  json  quot project id quot           Title string  json  quot title quot           Name string  json  quot name quot              func  p Project  String   string           return fmt Sprintf  quot  Id  d  Title  s  Name  s  quot   p Id  p Title  p Name             func main             o    Project Id  4  Name   quot hello quot   Title   quot world quot           fmt Printf  quot   v n quot   o         Happy Coding

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Maybe this shouldn t be applied for production requests but if you are on debugging mode I suggest you follow the below approach    marshalledText       json MarshalIndent inputStruct           fmt Println string marshalledText     This results in formatting the data in json format with increased readability

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I like litter   From their readme   type Person struct     Name   string   Age    int   Parent  Person    litter Dump Person    Name     Bob     Age     20    Parent   amp Person      Name   Jane       Age   50            Sdump is pretty handy in tests    func TestSearch t  testing T      result    DoSearch      actual    litterOpts Sdump result    expected  err    ioutil ReadFile  testdata txt     if err    nil          First run  write test data since it doesn t exist         if  os IsNotExist err          t Error err            ioutil Write  testdata txt   actual  0644      actual   expected       if expected    actual       t Errorf  Expected  s  got  s   expected  actual

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I recommend to use Pretty Printer Library  In that you can print any struct very easily    Install Library  https   github com kr pretty   or   go get github com kr pretty   Now do like this in your code  package main  import   fmt github com kr pretty    func main     type Project struct       Id int64  json  project id       Title string  json  title       Name string  json  name       Data Data  json  data       Commits Commits  json  commits      fmt Printf     v   pretty Formatter Project     It will print all struct details  fmt Printf     v   pretty Formatter Project Id     It will print component one by one       Also you can get difference between component through this library and so more  You can also have a look on library Docs here

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Without using external libraries and with new line after each field   log Println              strings Replace                  fmt Sprintf    v   post           n   -1

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There s also go-render  which handles pointer recursion and lots of key sorting for string and int maps    Installation   go get github com luci go-render render   Example   type customType int type testStruct struct           S string         V  map string int         I interface      a    testStruct          S   hello           V   amp map string int  foo   0   bar   1           I  customType 42      fmt Println  Render test    fmt Printf  fmt Printf       v n   a    fmt Printf  render Render   s n   Render a     Which prints   fmt Printf     render testStruct S  hello   V   map string int  0x600dd065   I 42  render Render  render testStruct S  hello   V   map string int   bar  1   foo  0   I render customType 42

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p   Project      fmt Printf    v   p  fmt Printf    v   p    with type

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fmt Println    v   structure variable    A better way to do this would be to create a global constant for the string    v  in a package called  commons  maybe  and use it everywhere in your code    In commons package const STRUCTURE DATA FMT      v     In your code everywhere fmt Println commons STRUCTURE DATA FMT  structure variable

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fmt Printf    v n   project    This is the basic way of printing the details

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very simple  I don t have the structure of Data and Commits So I changed the  package main  import        fmt     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         p    Project      1       First        Ankit        your data        Commit message             fmt Println p      For learning you can take help from here   https   gobyexample com structs

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my 2cents would be to use json MarshalIndent -- surprised this isn t suggested  as it is the most straightforward  for example   func prettyPrint i interface    string       s       json MarshalIndent i        t       return string s      no external deps and results in nicely formatted output

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Alternatively  try using this function PrettyPrint       print the contents of the obj func PrettyPrint data interface          var p   byte           var err    error     p  err    json MarshalIndent data        t       if err    nil           fmt Println err          return           fmt Printf   s  n   p      In order to use this you do not need any additional packages with the exception of fmt and encoding json  just a reference  pointer to  or literal of the struct you have created    To use just take your struct  initialize it in main or whatever package you are in and pass it into PrettyPrint      type Prefix struct       Network string     Mask    int    func valueStruct            struct as a value     var nw Prefix     nw Network    10 1 1 0      nw Mask   24     fmt Println      struct as a pointer           PrettyPrint  amp nw      It s output would be      struct as a pointer            Network    10 1 1 0        Mask   24      Play around with the code here

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Another way is  create a func called toString that takes struct  format the fields as you wish   import        fmt     type T struct       x  y string    func  r T  toString   string       return  Formate as u need      r x   r y    func main         r1    T  csa    ac       fmt Println  toStringed      r1 toString

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To print the struct as JSON  fmt Printf  quot   v n quot   yourProject   Also possible with  as it was mentioned above   fmt Printf  quot   v n quot   yourProject   But the second option prints string values without  quot  quot  so it is harder to read

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I want to recommend go-spew  which according to their github  Implements a deep pretty printer for Go data structures to aid in debugging   go get -u github com davecgh go-spew spew   usage example   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          o    Project Name   hello   Title   world       spew Dump o      output    main Project     Id   int64  0   Title   string   len 5   world    Name   string   len 5   hello    Data   string       Commits   string

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package main import  quot fmt quot   type Project struct       Id int64  json  quot id quot       Title string  json  quot title quot      func  p Project  String   string       return fmt Sprintf  quot  Id  d  Title  s  Name  s  quot   p Id  p Title     func main         var instance Project     Instance   Project Id  100  Title   quot Print Struct quot       fmt Printf  quot  v n quot   Instance

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type Response struct           UserId int     json  userId           Id     int     json  id           Title  string  json  title           Body   string  json  body              func PostsGet   gin HandlerFunc           return func c  gin Context                xs  err    http Get  https   jsonplaceholder typicode com posts               if err    nil                   log Println  The HTTP request failed with error     err                            data       ioutil ReadAll xs enter code here  Body                   this will print the struct in console                         fmt Println string data                    this is to send as response for the API             bytes      byte string data               var res   Response             json Unmarshal bytes   amp res               c JSON http StatusOK  res

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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     amp 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  amp t  Elem   typeOfT    s Type    for i    0  i  lt  s NumField    i         f    s Field i      fmt Printf   d   s  s    v n   i          typeOfT Field i  Name  f Type    f Interface

[struct] How to print struct variables in console?

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