c++ - 如何在C++中正确声明/分配变量的值

Question

在分配值之前，我应该在c++程序的顶部声明变量吗:

int i;
std::string x;
std::string retval;

x = "foo";
i = 5;
retval = somefunction();

或者通过以下方式将值分配给变量是否正确/可以接受:

int i = 5;
std::string x = "foo";
std::string retval = somefunction();

我是c++的新手，我想知道c++社区接受哪种方式。

Answer 1

第二种方法是更惯用的C++，应该首选。
另请参阅核心准则NR.1:

Reason

The “all declarations on top” rule is a legacy of old programming languages that didn’t allow initialization of variables and constants after a statement. This leads to longer programs and more errors caused by uninitialized and wrongly initialized variables.

它也更加有效，因为第一个是默认构造，然后是赋值，第二个是简单构造。