C++核心準(zhǔn)則C.83:對(duì)于值類類型,考慮提供一個(gè)不會(huì)拋出異常的交換...

C.83: For value-like types, consider providing a noexcept swap function

C.83:對(duì)于值類類型，考慮提供一個(gè)不會(huì)拋出異常的交換函數(shù)

Reason（原因）

A swap can be handy for implementing a number of idioms, from smoothly moving objects around to implementing assignment easily to providing a guaranteed commit function that enables strongly error-safe calling code. Consider using swap to implement copy assignment in terms of copy construction. See also destructors, deallocation, and swap must never fail.

移動(dòng)功能可以在實(shí)現(xiàn)很多常規(guī)操作時(shí)提供便利。從順暢地移動(dòng)對(duì)象到更容易地實(shí)現(xiàn)賦值，以至提供有保證的提交函數(shù)，這個(gè)函數(shù)可以為不會(huì)失敗的調(diào)用代碼提供強(qiáng)有力的支持。

Example, good（示例）

class Foo {
public:
 ? ?void swap(Foo& rhs) noexcept
 ? ?{
 ? ? ? ?m1.swap(rhs.m1);
 ? ? ? ?std::swap(m2, rhs.m2);
 ? ?}
private:
 ? ?Bar m1;
 ? ?int m2;
};

Providing a nonmember swap function in the same namespace as your type for callers' convenience.

為了調(diào)用者的方便，在和目標(biāo)類型同一個(gè)命名空間中提供一個(gè)非成員的swap函數(shù)。

void swap(Foo& a, Foo& b)
{
 ? ?a.swap(b);
}

Enforcement（實(shí)施建議）

• (Simple) A class without virtual functions should have a swap member function declared.

• (簡單)不包含虛函數(shù)的類就應(yīng)該定義一個(gè)swap函數(shù)。

• (Simple) When a class has a swap member function, it should be declared noexcept.

• (簡單)如果一個(gè)類包含一個(gè)swap成員函數(shù)，這個(gè)函數(shù)應(yīng)該被聲明為noexcept。

原文鏈接

https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#c83-for-value-like-types-consider-providing-a-noexcept-swap-function

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