C++核心准则C.49:构造函数中应该做的是初始化而不是赋值

C.49: Prefer initialization to assignment in constructors C.49:构造函数中应该做的是初始化而不是赋值

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.

初始化明确地表明所做的是初始化而不是赋值，而且可以做得更优美，更有效率。防止“赋值之前使用”的错误。

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:

相对于那些const char* s，我们应该可以使用gsl::string_span或者(C++17引入的）std::string_view作为表达函数参数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
    // ...
};

原文链接

https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#c49-prefer-initialization-to-assignment-in-constructors

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