int i = 0; // (a) Old C style should I use it?
int i{0}; // (b) Brace direct init
int i{}; // (c) Same as (b)
int i = {0}; // (d) as (b)
int i = {}; // (e) as (c)
auto i = 0; // (f) auto = int in this case.
auto i = int{0}; // (g) auto = more specific.
auto i = int{}; // (h) same as above (g)
使用哪一个?萨特说使用:
int i = 0;
auto i = 0;
为什么不:
int i = {0};
auto i = int{0};
并且在某些情况下我应该摆脱“ =”:
int i{0};
auto i{0}; // i is not what some might expect in this case. So I would prefer using "=" everywhere possible like int i = {0}; ...
编辑:这就是我的目标,在我看来,这是最一致的:
rectangle w = { origin(), extents() };
complex<double> c = { 2.71828, 3.14159 };
mystruct m = { 1, 2 };
int a[] = { 1, 2, 3, 4 };
vector<int> v = { 1, 2, 3, 4 };
point p = {}; // Default initializes members
int i = {0}; // Checked assembly for this and it's binary the same as int i{0}; could be written also as int i = {};
string s = {""}; // Same as string s = {}; (OR) string s;
现实生活中的例子:
std::string title = { pt.get<std::string>("document.window.title") };
const std::string file = { R"(CoreSettings.xml)" };
int_least64_t currentTick = { 0 }; // (OR) int_least64_t currentTick = {};
bool isRunning = { false }; // (OR) bool isRunning = {};
App* app = { nullptr }; // (OR) App* app = {};
Event event = {};
double detectedFrameRate = { 1000000000.0 / (swapIntervalDeltaCumulative / 20.0) };
double precision = { static_cast<double>(boost::chrono::high_resolution_clock::period::num)
/ boost::chrono::high_resolution_clock::period::den };
auto timeSpan = boost::chrono::duration_cast<boost::chrono::nanoseconds>(nowTime - startTime);
替代方法是:
std::string title { pt.get<std::string>("document.window.title") };
const std::string file { R"(CoreSettings.xml)" };
int_least64_t currentTick { 0 }; // (OR) int_least64_t currentTick{};
bool isRunning { false }; // (OR) bool isRunning{};
App* app { nullptr }; // (OR) App* app{};
Event event {};
double detectedFrameRate { 1000000000.0 / (swapIntervalDeltaCumulative / 20.0) };
double precision { static_cast<double>(boost::chrono::high_resolution_clock::period::num)
/ boost::chrono::high_resolution_clock::period::den };
auto timeSpan = boost::chrono::duration_cast<boost::chrono::nanoseconds>(nowTime - startTime);
如果不使用花括号,则丑陋或容易出错:
int_least64_t currentTick = 0; // C style - changed this from double to int recently and compiler did not complain so I had something like int_least64_t currentTick = 0.0; ugly!
bool isRunning = false; // C style
App* app = nullptr; // C mixed with C++11 style;
Event event; // might not be initialized by all compilers
int someInt = func(); // func() returns double no error but narrowing.
对于简单的事情(例如int
您的示例),我同意
int i=0;
可能是最常被理解的(在程序员中),但是使用大括号初始化有很多优点,对我来说,使括号更可取。例如
int i = 3.99; // i gets 3; no warning, no error
int i{3.99}; // i gets 3; warning: "narrowing conversion"
它有助于编写更多无错误的代码,因此在我看来是一种更好的方法。
与之混合会auto
更加危险。我通常auto
仅用于:
for (const auto &n : mycollection)
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我来说两句