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util.go
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util.go
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package form
import (
"fmt"
"reflect"
"strings"
"golang.org/x/net/html"
)
// attr is a utility for appending attributes.
func attr(a []html.Attribute, n, v string) []html.Attribute {
return append(a, html.Attribute{Key: n, Val: v})
}
// toAttr tries to turn whatever is passed in into an HTML attribute.
func toAttr(o interface{}) (html.Attribute, bool) {
v := reflect.Indirect(reflect.ValueOf(o))
if v.IsNil() {
return html.Attribute{}, false
}
if val, ok := aval(o); ok {
t := v.Type()
return html.Attribute{Key: strings.ToLower(t.Name()), Val: val}, true
}
return html.Attribute{}, false
}
// aval converts a value to an attribute string value
//
// The key is the lowercased name of the thing.
//
// The values are calculated as follows:
//
// - Bools become "true" and "false" strings
// - Numeric types are converted to strings
// - Strings are omitted if the len() == 0, or encoded as-is
//
// Anything else returns an empty string, and a false .
func aval(o interface{}) (string, bool) {
v := reflect.Indirect(reflect.ValueOf(o))
switch v.Kind() {
case reflect.Bool:
if v.Bool() == true {
return "true", true
}
return "false", true
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Uint, reflect.Uint16, reflect.Uint32, reflect.Uint64:
return fmt.Sprintf("%d", o), true
case reflect.Float32, reflect.Float64:
return fmt.Sprintf("%f", o), true
case reflect.String:
o := o.(string)
if len(o) == 0 {
return o, false
}
return o, true
}
println("Did not match type.")
return "", false
}
// structToAttrs converts fields on a struct into attributes.
// Given a struct and a list of field names, convert to HTML attributes.
func structToAttrs(s interface{}, names ...string) []html.Attribute {
c := make(map[string]struct{}, len(names))
for _, n := range names {
c[n] = struct{}{}
}
v := reflect.Indirect(reflect.ValueOf(s))
if v.Kind() != reflect.Struct {
return []html.Attribute{}
}
nf := v.NumField()
a := []html.Attribute{}
for i := 0; i < nf; i++ {
fv := v.Field(i)
fn := v.Type().Field(i).Name
if _, ok := c[fn]; ok {
if v, ok := aval(fv.Interface()); ok {
a = attr(a, strings.ToLower(fn), v)
}
}
}
return a
}