adimpression/structs

Utilities for Go structs

Archived project. No maintenance.

This project is not maintained anymore and is archived. Feel free to fork and make your own changes if needed. For more detail read my blog post: Taking an indefinite sabbatical from my projects

Thanks to everyone for their valuable feedback and contributions.

Structs

Structs contains various utilities to work with Go (Golang) structs. It was initially used by me to convert a struct into a map[string]interface{}. With time I've added other utilities for structs. It's basically a high level package based on primitives from the reflect package. Feel free to add new functions or improve the existing code.

Install

go get github.com/fatih/structs

Usage and Examples

Just like the standard lib strings, bytes and co packages, structs has many global functions to manipulate or organize your struct data. Lets define and declare a struct:

type Server struct {
	Name        string `json:"name,omitempty"`
	ID          int
	Enabled     bool
	users       []string // not exported
	http.Server          // embedded
}

server := &Server{
	Name:    "gopher",
	ID:      123456,
	Enabled: true,
}

// Convert a struct to a map[string]interface{}
// => {"Name":"gopher", "ID":123456, "Enabled":true}
m := structs.Map(server)

// Convert the values of a struct to a []interface{}
// => ["gopher", 123456, true]
v := structs.Values(server)

// Convert the names of a struct to a []string
// (see "Names methods" for more info about fields)
n := structs.Names(server)

// Convert the values of a struct to a []*Field
// (see "Field methods" for more info about fields)
f := structs.Fields(server)

// Return the struct name => "Server"
n := structs.Name(server)

// Check if any field of a struct is initialized or not.
h := structs.HasZero(server)

// Check if all fields of a struct is initialized or not.
z := structs.IsZero(server)

// Check if server is a struct or a pointer to struct
i := structs.IsStruct(server)

Struct methods

The structs functions can be also used as independent methods by creating a new *structs.Struct. This is handy if you want to have more control over the structs (such as retrieving a single Field).

// Create a new struct type:
s := structs.New(server)

m := s.Map()              // Get a map[string]interface{}
v := s.Values()           // Get a []interface{}
f := s.Fields()           // Get a []*Field
n := s.Names()            // Get a []string
f := s.Field(name)        // Get a *Field based on the given field name
f, ok := s.FieldOk(name)  // Get a *Field based on the given field name
n := s.Name()             // Get the struct name
h := s.HasZero()          // Check if any field is uninitialized
z := s.IsZero()           // Check if all fields are uninitialized

Field methods

We can easily examine a single Field for more detail. Below you can see how we get and interact with various field methods:

s := structs.New(server)

// Get the Field struct for the "Name" field
name := s.Field("Name")

// Get the underlying value,  value => "gopher"
value := name.Value().(string)

// Set the field's value
name.Set("another gopher")

// Get the field's kind, kind =>  "string"
name.Kind()

// Check if the field is exported or not
if name.IsExported() {
	fmt.Println("Name field is exported")
}

// Check if the value is a zero value, such as "" for string, 0 for int
if !name.IsZero() {
	fmt.Println("Name is initialized")
}

// Check if the field is an anonymous (embedded) field
if !name.IsEmbedded() {
	fmt.Println("Name is not an embedded field")
}

// Get the Field's tag value for tag name "json", tag value => "name,omitempty"
tagValue := name.Tag("json")

Nested structs are supported too:

addrField := s.Field("Server").Field("Addr")

// Get the value for addr
a := addrField.Value().(string)

// Or get all fields
httpServer := s.Field("Server").Fields()

We can also get a slice of Fields from the Struct type to iterate over all fields. This is handy if you wish to examine all fields:

s := structs.New(server)

for _, f := range s.Fields() {
	fmt.Printf("field name: %+v\n", f.Name())

	if f.IsExported() {
		fmt.Printf("value   : %+v\n", f.Value())
		fmt.Printf("is zero : %+v\n", f.IsZero())
	}
}

Credits

• Fatih Arslan
• Cihangir Savas

License

The MIT License (MIT) - see LICENSE.md for more details