C++核心準(zhǔn)則C.49:構(gòu)造函數(shù)中應(yīng)該做的是初始化而不是賦值

C.49: Prefer initialization to assignment in constructors
C.49:構(gòu)造函數(shù)中應(yīng)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(yōu)美，更有效率。防止“賦值之前使用”的錯(cuò)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(duì)于那些const char* s，我們應(yīng)該可以使用gsl::string_span或者(C++17引入的）std::string_view作為表達(dá)函數(shù)參數(shù)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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