我的构造函数需要std::array
。我试图给它一个默认值,但调用不带参数的构造函数会出现此错误:
$ g++ -std=c++11 -Wall -Werror -Wextra -pedantic-errors test.cpp Position.cpp -o test
test.cpp: In function ‘int main()’:
test.cpp:14:29: error: array must be initialized with a brace-enclosed initializer
Position *y = new Position();
^
test.cpp:14:29: error: too many initializers for ‘std::array<unsigned char, 8ul>’
行号不同。这是我的代码:
// test.cpp
int main() {
Position *x = new Position({1,1,1,1,1,1,1,1}); // works
Position *y = new Position(); // does not work
}
// Position.cpp
#include <cstdint>
#include <array>
#include "Position.h"
Position::Position( std::array<uint8_t,8> columns_ ) {
columns = columns_;
}
// Position.h
#ifndef POSITION_H
#define POSITION_H
#include <array>
class Position {
public:
Position( std::array<uint8_t,8> = {0,0,0,0,0,0,0,0} );
private:
std::array<uint8_t,8> columns;
};
#endif
我有什么问题?
答案 0 :(得分:5)
您需要重复以下类型:
Position( std::array<uint8_t,8> = std::array<uint8_t,8>{0,0,0,0,0,0,0,0} );
当这个(或使用双括号)工作时,它会在默认情况下在每个调用方的侧面创建一个副本。重载的构造函数会避免这种代码膨胀,因此我建议优先选择重载而不是默认参数。
答案 1 :(得分:4)
第二个案例运行所需的双括号:
Position( std::array<uint8_t,8> = {{0,0,0,0,0,0,0,0}} );