C.49: Prefer initialization to assignment in constructors
C.49:構造函數中應該做的是初始化而不是賦值
Reason（原因）
An initialization explicitly states that initialization, rather than assignment, is done and can be more elegant and efficient. Prevents "use before set" errors.
初始化明確地表明所做的是初始化而不是賦值，而且可以做得更優美，更有效率。防止“賦值之前使用”的錯誤。
Example, good（良好示例）
class A { // Good
string s1;
public:
A(czstring p) : s1{p} { } // GOOD: directly construct (and the C-string is explicitly named)
// ...
};
Example, bad（反面示例）
class B { // BAD
string s1;
public:
B(const char* p) { s1 = p; } // BAD: default constructor followed by assignment
// ...
};
class C { // UGLY, aka very bad
int* p;
public:
C() { cout << *p; p = new int{10}; } // accidental use before initialized
// ...
};
Example, better still（更好的示例）
Instead of those const char*s we could use gsl::string_span or (in C++17) std::string_view as a more general way to present arguments to a function:
相對於那些const char* s，我們應該可以使用gsl::string_span或者(C++17引入的）std::string_view作爲表達函數參數怒的更加普遍的方式（https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#Rstr-view）。
class D { // Good
string s1;
public:
A(string_view v) : s1{v} { } // GOOD: directly construct
// ...
};
原文鏈接
https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#c49-prefer-initialization-to-assignment-in-constructors
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