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c++11中auto&&是什么意思（）

为什么80%的码农都做不了架构师？>>>c++11中auto&&是什么意思（）
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By using auto&& var = you are saying: I will accept any initializer regardless of whether it is an lvalue or rvalue expression and I will preserve its constness. This is typically used for forwarding (usually with T&&). The reason this works is because a "universal reference", auto&& or T&&, will bind to anything.
You might say, well why not just use a const auto& because that will also bind to anything? The problem with using a const reference is that it's const! You won't be able to later bind it to any non-const references or invoke any member functions that are not marked const.
As an example, imagine that you want to get a std::vector, take an iterator to its first element and modify the value pointed to by that iterator in some way:
auto&& vec = some_expression_that_may_be_rvalue_or_lvalue; auto i = std::begin(vec); (*i)++; This code will compile just fine regardless of the initializer expression. The alternatives to auto&& fail in the following ways:
auto => will copy the vector, but we wanted a reference auto& => will only bind to modifiable lvalues const auto& => will bind to anything but make it const, giving us const_iterator const auto&& => will bind only to rvalues So for this, auto&& works perfectly! An example of using auto&& like this is in a range-based for loop.
【c++11中auto&&是什么意思（）】转载于:https://my.oschina.net/itfanr/blog/1791379

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