explicit specifier
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指定构造函数和（C++11 起）转换运算符，不允许隐式转换
Original:
Specifies constructors and （C++11 起） conversion operators that don't allow implicit conversions
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[编辑] 语法
| explicit class_name ( params ) | |||||||||
| explicit operator type ( ) （C++11 起） | |||||||||
[编辑] 为例
struct A { A ( int ) {} operator int() const { return 0; } }; struct B { explicit B(int) {} explicit operator int() const { return 0; } }; int main() { // A is has no explicit ctor / conversion, everything is fine A a1 = 1; A a2 ( 2 ); A a3 { 3 }; int na1 = a1; int na2 = static_cast<int>( a1 ); B b1 = 1; // Error: implicit conversion from int to B B b2 ( 2 ); // OK: explicit constructor call B b3 { 3 }; // OK: explicit constructor call int nb1 = b2; // Error: implicit conversion from B to int int nb2 = static_cast<int>( b2 ); // OK: explicit cast }
