func fmtStruct()

Create readable multiline formatted dump of any Golang structure using the fmtStruct() func.

Introduction

When debugging a go program it can be handy to dump an entire data structure with as much detail as possible. This program demonstrates a function that provides detailed output in a string, so it is easy to log, print or even display on a web page. Here is some example output:

Sample Movie Data:
[000]  &main.Lib{
[001]    Movies:[]main.Movie{
[002]      main.Movie{
[003]        Name:"Moby Dick",
[004]        UPC:2761686294,
[005]        ISBN:0-7928-5014-9,
[006]        pubYear:1956,
[007]        director:"John Huston",
[008]        cost:19.95,
[009]        copies:3
[010]      },
[011]      main.Movie{
[012]        Name:"Firewall",
[013]        UPC:1256959410,
[014]        ISBN:1-4198-0220-8,
[015]        pubYear:2006,
[016]        director:"Richard Loncraine",
[017]        cost:10.45,
[018]        copies:1
[019]      },
[020]      main.Movie{
[021]        Name:"The Exorcist",
[022]        UPC:8539186322,
[023]        ISBN:0-7907-5167-4,
[024]        pubYear:1973,
[025]        director:"William Friedkin",
[026]        cost:12.98,
[027]        copies:1
[028]      }
[029]    },
[030]    totalCount:5,
[031]    maxIncome:54.32
[032]  }

How it works

The standard Golang fmt package does the heavy lifting, extracting the details of the data structure, and formating it using the Go-syntax representation of the value. This is then post processed to add new line characters, line numbers and indentation. Because the go-syntax formatting is used it is possible to add GoString stringers to user defined types to improve readability even further, as demonstrated in the main program.

Usage

The following go program excerpt shows the use of fmtStruct():

	simple := struct{
		count int
		name string
		cost floar64
	}{
		count: 45
		name: "Billy"
		cost "28.95"
	}
	// print out simple after formatting with fmtStruct()
	fmt.Print(fmtStruct(adata))

This produces the following output:

Structure dump. . .:
[0000]  struct {
[0001]    count int; name string; cost float64
[0002]  }{
[0003]    count:45,
[0004]    name:"Billy",
[0005]    cost:28.95
[0006]  }

The demonstration program shows this example and a more complex example which demonstrates the use of user defined GoStringers to enhance readability even further.