<p>Go泛型通過類型參數(shù)和約束實(shí)現(xiàn)代碼復(fù)用與類型安全。類型參數(shù)是聲明泛型函數(shù)或類型時(shí)使用的類型占位符，如func Print[T any]允許接受任何類型；約束定義類型需支持的操作，如Number接口限制為數(shù)字類型以確保運(yùn)算有效；Go 1.21 提供內(nèi)置約束如constraints.Ordered用於可比較類型；自定義約束可通過接口規(guī)範(fàn)方法調(diào)用；約束不僅限制類型範(fàn)圍，還確保泛型代碼內(nèi)操作合法，避免運(yùn)行時(shí)錯(cuò)誤。使用時(shí)應(yīng)優(yōu)先選用內(nèi)置約束，並確保函數(shù)僅依賴約束保證的特性。 </p> <p><img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175312609333761.jpg" class="lazy" alt="What are the constraints and type parameters in Go generics?"></p> <p> Go generics introduced in Go 1.18 brought a powerful new way to write reusable code, and with them came the concepts of <strong>type parameters</strong> and <strong>constraints</strong> . Let's break down what these mean and how they work together. </p> <img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175312609452134.jpeg" class="lazy" alt="What are the constraints and type parameters in Go generics?"><hr> <h3 id="What-Are-Type-Parameters"> What Are Type Parameters?</h3> <p> Type parameters are placeholders for types that you define when declaring a generic function or type. They allow you to write code that works with any type, as long as it meets certain criteria.</p> <p> For example: </p> <img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175312609561807.jpeg" class="lazy" alt="What are the constraints and type parameters in Go generics?"><pre class='brush:php;toolbar:false;'> func Print[T any](s []T) { for _, v := range s { fmt.Println(v) } }</pre><p> Here, <code>T</code> is a type parameter. The <code>any</code> constraint means this function will accept any type for <code>T</code> .</p><p> You can use multiple type parameters too: </p><img src="/static/imghw/default1.png" data-src="https://img.php.cn/upload/article/000/000/000/175312609646538.jpeg" class="lazy" alt="What are the constraints and type parameters in Go generics?" /><pre class='brush:php;toolbar:false;'> func Pair[A any, B any](a A, b B) (A, B) { return a, b }</pre><hr /><h3 id="What-Are-Constraints"> What Are Constraints?</h3><p> Constraints define what operations a type argument must support. They're not just about restricting types — they also tell Go what methods or operators are safe to use inside your generic code.</p><p> In early versions of Go generics, constraints were defined using interface types. For example:</p><pre class='brush:php;toolbar:false;'> type Number interface { int | int8 | int16 | int32 | int64 | uint | uint8 | uint16 | uint32 | uint64 | float32 | float64 }</pre><p> This constraint allows any numeric type.</p><p> Then you could write a function like:</p><pre class='brush:php;toolbar:false;'> func Sum[T Number](a, b T) T { return ab }</pre><p> Without the <code>Number</code> constraint, Go wouldn't know if the<code> </code>operator was valid for type <code>T</code> .</p><hr /><h3 id="Built-in-Constraints"> Built-in Constraints</h3><p> Go provides some useful built-in constraints in the <code>constraints</code> package (requires Go 1.21 ):</p><ul><li> <code>constraints.Ordered</code> – for types that can be compared with <code><</code> , <code>></code> , etc.</li><li> <code>constraints.Integer</code> – all integer types</li><li> <code>constraints.Float</code> – float32 and float64</li></ul><p> So instead of writing out <code>int | float64 | ...</code> , you can do:</p><pre class='brush:php;toolbar:false;'> func Min[T constraints.Ordered](a, b T) T { if a < b { return a } return b }</pre><hr /><h3 id="Why-Constraints-Matter"> Why Constraints Matter</h3><p> Constraints aren't just for filtering types — they're essential for letting Go understand what operations are valid within your generic code.</p><p> Without a proper constraint, you might write something like this:</p><pre class='brush:php;toolbar:false;'> func Add[T any](a, b T) T { return ab // Compile error: operator not defined for T }</pre><p> That won't compile because Go doesn't know if <code>T</code> supports<code> </code>. So you need to add a constraint that includes types supporting addition.</p> <p> Also:</p> <ul> <li> You can create your own interfaces to enforce method calls.</li> <li> Constraints let you ensure types implement specific behaviors.</li> <li> They help avoid runtime errors by catching issues at compile time.</li> </ul> <hr> <h3 id="Summary"> Summary</h3> <p> Type parameters let you write code that works with any type. Constraints make sure those types behave the way your code expects. Together, they bring flexibility and safety to Go generics.</p> <p> Use built-in constraints where possible, define your own when needed, and always make sure your functions only assume what's guaranteed by the constraints.</p> <p>基本上就這些。</p>

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