Go (golang) package which provides reflection abstractions beyond the Go standard library.
Metaflector makes it easy to inspect objects and structs, and programmatically access structural data.
To be precise, this package currently provides:
- Generating a dot-separated list of struct hierarchical properties
metaflector.TerminalFields(&http.Server{})
// Output: []string{"Addr", "IdleTimeout", "MaxHeaderBytes", "ReadHeaderTimeout", "ReadTimeout", "WriteTimeout"}- Iterating over a struct or slice or array objects' fields
metaflector.EachField(http.Server{}, func(obj interface{}, name string, kind reflect.Kind) {
fmt.Printf("obj=%v name=%v kind=%v\n", obj, name, kind)
})
// Output:
// obj= name=Addr kind=string
// obj=<nil> name=TLSConfig kind=struct
// obj=0 name=ReadTimeout kind=int64
// obj=0 name=ReadHeaderTimeout kind=int64
// obj=0 name=WriteTimeout kind=int64
// obj=0 name=IdleTimeout kind=int64
// obj=0 name=MaxHeaderBytes kind=int
// obj=map[] name=TLSNextProto kind=map
// obj=<nil> name=ErrorLog kind=struct- Dynamic property extraction based on dot-paths
e.g.
Get(myVar, "A.Nested.Property")I've found this functionality useful for automatically applying user input as search filters against arbitrary structs in command-line progreams.
See the docs for more info.
Created by Jay Taylor and used by Gigawatt.
-
For heterogeneous collections (i.e. this is possible via
[]interface{}), only the structure of the first non-nil slice or array element will be considered. -
No maps support [yet].
- Go version 1.6 or newer
go test ./...
package main
import (
"fmt"
"reflect"
"github.com/gigawattio/metaflector"
)
type (
Foo struct {
Bar Bar
Name string
}
Bar struct {
ID string
private string
}
)
var foo = &Foo{
Bar: Bar{
ID: "2017",
private: "this isn't exported",
},
Name: "meta",
}
func main() {
fmt.Printf("foo TerminalFields: %# v\n", metaflector.TerminalFields(foo))
fmt.Printf("Bar.ID resolved to: %v\n", metaflector.Get(foo, "Bar.ID"))
metaflector.EachField(foo, func(obj interface{}, name string, kind reflect.Kind) {
fmt.Printf("obj=%v == Get(obj, %q) ? %v\n", obj, name, reflect.DeepEqual(obj, metaflector.Get(foo, name)))
})
fmt.Printf("Get()=%v\n", metaflector.Get(foo, "Name"))
}
// Output:
// foo TerminalFields: []string{"Bar.ID", "Name"}
// Bar.ID resolved to: 2017
// obj={2017 this isn't exported} == Get(obj, "Bar") ? true
// obj=meta == Get(obj, "Name") ? true
// Get()=metaSee the tests for more examples.
The reflections package is related and complementary.
Permissive MIT license, see the LICENSE file for more information.