boost :: optional vs boost :: make_optional [英] boost::optional vs boost::make_optional

问题描述

我想更好地理解使用 default 构造函数创建 boost :: optional 对象之间的区别:

I would like to understand better the difference between creating a boost::optional object using the default constructor:

boost::optional<PastaType> pasta = boost::optional<PastaType>(spaghetti)

或使用 make_optional 版本:

boost::optional<PastaType> pasta = boost::make_optional<PastaType>(spaghetti)

环顾四周，我只是理解使用 make_optional 版本PastaType不能是引用类型，但是我想弄清楚何时使用其中一种.

Looking around I just understoood that with the make_optional version PastaType cannot be a reference type, but I would like to figure out better when to use one or the other.

谢谢！

推荐答案

make_optional 是一种便利或帮助功能，可以通过推断的模板参数来减少必须编写的代码量>可选.在功能上，这两种方法是等效的.

make_optional is a convenience or helper function that can reduce the amount of code you have to write by inferring the template parameter of optional. Functionally the two methods are equivalent.

auto pasta = boost::make_optional(spaghetti);

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