mirror of
https://github.com/gopl-zh/gopl-zh.github.com.git
synced 2024-11-05 14:03:45 +00:00
54 lines
1.1 KiB
Go
54 lines
1.1 KiB
Go
// Copyright © 2016 Alan A. A. Donovan & Brian W. Kernighan.
|
|
// License: https://creativecommons.org/licenses/by-nc-sa/4.0/
|
|
|
|
// See page 160.
|
|
|
|
// The urlvalues command demonstrates a map type with methods.
|
|
package main
|
|
|
|
/*
|
|
//!+values
|
|
package url
|
|
|
|
// Values maps a string key to a list of values.
|
|
type Values map[string][]string
|
|
|
|
// Get returns the first value associated with the given key,
|
|
// or "" if there are none.
|
|
func (v Values) Get(key string) string {
|
|
if vs := v[key]; len(vs) > 0 {
|
|
return vs[0]
|
|
}
|
|
return ""
|
|
}
|
|
|
|
// Add adds the value to key.
|
|
// It appends to any existing values associated with key.
|
|
func (v Values) Add(key, value string) {
|
|
v[key] = append(v[key], value)
|
|
}
|
|
//!-values
|
|
*/
|
|
|
|
import (
|
|
"fmt"
|
|
"net/url"
|
|
)
|
|
|
|
func main() {
|
|
//!+main
|
|
m := url.Values{"lang": {"en"}} // direct construction
|
|
m.Add("item", "1")
|
|
m.Add("item", "2")
|
|
|
|
fmt.Println(m.Get("lang")) // "en"
|
|
fmt.Println(m.Get("q")) // ""
|
|
fmt.Println(m.Get("item")) // "1" (first value)
|
|
fmt.Println(m["item"]) // "[1 2]" (direct map access)
|
|
|
|
m = nil
|
|
fmt.Println(m.Get("item")) // ""
|
|
m.Add("item", "3") // panic: assignment to entry in nil map
|
|
//!-main
|
|
}
|