<blockquote><p>比較方法：1、直接使用“==”運算子比較，語法“str1 == str2”，該方法區分大小寫。 2.利用strings套件的Compare()函數比較，語法「strings.Compare(a,b)」；傳回值為int型別，0表示兩數相等，1表示a大於b，「-1」表示a小於b 。 3.利用strings套件的EqualFold()比較，語法「strings.EqualFold(a,b)」。 </p></blockquote>
<p><img src="https://img.php.cn/upload/article/000/000/024/63c224119dee6813.jpg" alt="go語言怎麼比較字串" ></p>
<p>本教學操作環境：windows7系統、GO 1.18版本、Dell G3電腦。 </p>
<h2><strong>Go語言比較字串方式</strong></h2>
<p>在go 語言中字串比較的方式有以下三種：</p>
<ul class="ul-level-0">
<li>
<code> ==</code> 直接比較，區分大小寫</li>
<li>
<code>strings.Compare(a,b)</code> 此函數傳回值為int, 0 表示兩數相等，1 表示a>b, -1 表示a<b><li>
<code>strings.EqualFold(a,b)</code> 直接回傳是否相等，不區分大小寫。 </li></b>
</li>
</ul>
<p>範例如下：<span style="background-color: rgb(248, 248, 248);">// 1-使用等號比較－區分大消息</span></p>
<div class="developer-code-block">#<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:js;toolbar:false;">func Equal(s1, s2 string) bool {
return s1 == s2
}
// 2-使用 compare 比较——区分大小写
func Compare(s1, s2 string) bool {
return strings.Compare(s1, s2) == 0 //
}
//3-EqualFold 比较——不区分大小写. case-fold 即大小写同一处理
func EqualFold(s1, s2 string) bool {
return strings.EqualFold(s1, s2)
}
// 使用等号比较——忽略大小写
func Equal2(s1, s2 string) bool {
return strings.ToLower(s1) == strings.ToLower(s2)
}
// 使用 compare 比较——不区分大小写
func Compare2(s1, s2 string) bool {
return strings.Compare(strings.ToLower(s1), strings.ToLower(s2)) == 0
}
func StringCompareTest() {
fmt.Println("== 区分大小写", Equal("go", "Go")) //false
fmt.Println("== 忽略大小写",Equal2("go", "Go")) //true
fmt.Println("compare 区分大小写",Compare("go", "Go")) //false
fmt.Println("compare 忽略大小写",Compare2("go", "Go")) //true
fmt.Println("EqualFold 忽略大小写",EqualFold("go", "Go")) // true
}</pre><div class="contentsignin">登入後複製</div></div></div><h2><strong>效能比較</strong></h2><p>下面的程式碼使用Benchmark 做簡單的效能比較，測試專案的目錄結構為：</p><p><img src="https://img.php.cn/upload/image/916/800/564/167367265364778go語言怎麼比較字串" title="167367265364778go語言怎麼比較字串" alt="go語言怎麼比較字串"/></p><p>詳細程式碼：</p><div class="developer-code-block"> <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:js;toolbar:false;">package test
import (
"../str"
"testing"
)
func BenchmarkStrEqual(b *testing.B) {
for i := 0; i < b.N; i++ {
str.Equal("go", "Go")
}
}
func BenchmarkStrEqual2(b *testing.B) {
for i := 0; i < b.N; i++ {
str.Equal2("go", "Go")
}
}
func BenchmarkStrCompare(b *testing.B) {
for i := 0; i < b.N; i++ {
str.Compare("go", "Go")
}
}
func BenchmarkStrCompare2(b *testing.B) {
for i := 0; i < b.N; i++ {
str.Compare2("go", "Go")
}
}
func BenchmarkStrEqualFold(b *testing.B) {
for i := 0; i < b.N; i++ {
str.EqualFold("go", "Go")
}
}</pre><div class="contentsignin">登入後複製</div></div></div><p>測試結果如下：</p><p><img src="https://img.php.cn/upload/image/725/103/124/1673672666716944.png" title="1673672666716944.png" alt="go語言怎麼比較字串"/></p><p>透過上圖可以看出，效率最高的還是==</p><h2><strong>原始碼簡單分析</strong></h2><h4 id="3.1-strings.Compare" name="3.1-strings.Compare"><strong>1、strings.Compare</strong></h4><div class="developer-code-block"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:js;toolbar:false;">package strings
// Compare returns an integer comparing two strings lexicographically.
// The result will be 0 if a==b, -1 if a < b, and +1 if a > b.
//
// Compare is included only for symmetry with package bytes.
// It is usually clearer and always faster to use the built-in
// string comparison operators ==, <, >, and so on.
func Compare(a, b string) int {
// NOTE(rsc): This function does NOT call the runtime cmpstring function,
// because we do not want to provide any performance justification for
// using strings.Compare. Basically no one should use strings.Compare.
// As the comment above says, it is here only for symmetry with package bytes.
// If performance is important, the compiler should be changed to recognize
// the pattern so that all code doing three-way comparisons, not just code
// using strings.Compare, can benefit.
if a == b {
return 0
}
if a < b {
return -1
}
return +1
}</pre><div class="contentsignin">登入後複製</div></div></div><p>如上所示，我們發現，Compare 內部也是呼叫了<code>= =</code> , 而且函數的註解中也說了，這個函數only for symmetry with package bytes。而且推薦我們直接使用 <code>==</code> 和 <code>></code>、<code><</code>。 </p><h4 id="3.2-strings.EqualFold" name="3.2-strings.EqualFold"><strong>2、strings.EqualFold</strong></h4><div class="developer-code-block"><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:js;toolbar:false;">// EqualFold reports whether s and t, interpreted as UTF-8 strings,
// are equal under Unicode case-folding, which is a more general
// form of case-insensitivity.
func EqualFold(s, t string) bool {
for s != "" && t != "" {
// Extract first rune from each string.
var sr, tr rune
if s[0] < utf8.RuneSelf {
sr, s = rune(s[0]), s[1:]
} else {
r, size := utf8.DecodeRuneInString(s)
sr, s = r, s[size:]
}
if t[0] < utf8.RuneSelf {
tr, t = rune(t[0]), t[1:]
} else {
r, size := utf8.DecodeRuneInString(t)
tr, t = r, t[size:]
}
// If they match, keep going; if not, return false.
// Easy case.
if tr == sr {
continue
}
// Make sr < tr to simplify what follows.
if tr < sr {
tr, sr = sr, tr
}
// Fast check for ASCII.
if tr < utf8.RuneSelf {
// ASCII only, sr/tr must be upper/lower case
if 'A' <= sr && sr <= 'Z' && tr == sr+'a'-'A' {
continue
}
return false
}
// General case. SimpleFold(x) returns the next equivalent rune > x
// or wraps around to smaller values.
r := unicode.SimpleFold(sr)
for r != sr && r < tr {
r = unicode.SimpleFold(r)
}
if r == tr {
continue
}
return false
}
// One string is empty. Are both?
return s == t
}</pre><div class="contentsignin">登入後複製</div></div></div>
<p>這個函數中做了一系列操作，將兩個字串轉換成<code>utf -8</code> 字串進行比較，並且在比較時忽略大小寫。 </p>
<h2><strong>總結</strong></h2>
<p>透過上面的簡單總結與分析，我們發現，字串比較還是直接用== 、>、 </p>
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