Summary:
changelog: [internal]
You can read more about this rule on https://clang.llvm.org/extra/clang-tidy/checks/modernize-pass-by-value.html
# Isn't it wasteful to copy? Isn't reference more efficient?
This rule of thumb is no longer true since C++11 with move semantics. Let's look at some examples.
# Option one
```
class TextHolder
{
public:
TextBox(std::string const &text) : text_(text) {}
private:
std::string text_;
};
```
By using reference here, we prevent the caller from using rvalue to and avoiding copy. Regardless of what the caller passes in, copy always happens.
# Option two
```
class TextHolder
{
public:
TextBox(std::string const &text) : text_(text) {}
TextBox(std::string &&text) : text_(std::move(text)) {}
private:
std::string text_;
};
```
Here, we provide two constructors, one for const reference and one for rvalue reference. This gives the caller option to avoid copy. But now we have two constructors, which is not ideal.
# Option three (what we do in this diff)
```
class TextHolder
{
public:
TextBox(std::string text) : text_(std::move(text)) {}
private:
std::string text_;
};
```
Here, the caller has option to avoid copy and we only have single constructor.
Reviewed By: fkgozali, JoshuaGross
Differential Revision: D33276841
fbshipit-source-id: 619d5123d2e28937b22874650366629f24f20a63
5fa6c5a941