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