我正在嘗試取消參考存盤在靜態陣列中的方法指標并從方法中呼叫它，但出現以下錯誤：
error: 'chip8::Chip8::table[0]' cannot be used as a member pointer, since it is of type 'void (*)()'
(this->*table[0])();
^
這是我的班級宣告（chip.hpp）：
class Chip8{
private:
static void (*table[16])(); //function pointer table
//...
public:
void cycle();
//...
};
以下是 Chip8::cycle 和 Chip8::table (chip.cpp) 的實作：
void (Chip8::*table[16])() = {
&Chip8::opcode0,
&Chip8::JP_1nnn,
&Chip8::CALL_2nnn,
&Chip8::SE_3xkk,
&Chip8::SNE_4xkk,
&Chip8::SE_5xy0,
&Chip8::LD_6xkk,
&Chip8::ADD_7xkk,
&Chip8::opcode8,
&Chip8::SNE_9xy0,
&Chip8::LD_Annn,
&Chip8::JP_Bnnn,
&Chip8::RND_Cxkk,
&Chip8::DRW_Dxyn,
&Chip8::opcodeE,
&Chip8::opcodeF
};
void Chip8::cycle(){
opcode = (memory[pc] << 8) | memory[pc 1];
pc =2;
(this->*table[0])(); // error here
if(dt > 0){
dt--;
}
if(st > 0){
st--;
}
}
編輯：這是分配給表的函式的宣告：
//Function table extensions
void opcode0();
void opcode8();
void opcodeE();
void opcodeF();
//Instructions
void CLS_00E0(); // Clears screen
void RET_00EE(); // Pops new pc off the stack
void JP_1nnn(); // Jumps to nnn
void CALL_2nnn(); // Pushes current pc to stack and jumps to nnn
void SE_3xkk(); // Skip next instruction if Vx = kk
void SNE_4xkk(); // Skip next instruction if Vx != kk
void SE_5xy0(); // Skip next instruction if Vx == Vy
void LD_6xkk(); // Set Vx = kk
void ADD_7xkk(); // Vx = kk
void LD_8xy0(); // Vx = Vy
void OR_8xy1(); // Vx |= Vy
void AND_8xy2(); // Vx &= Vy
void XOR_8xy3(); // Vx ^= Vy
void ADD_8xy4(); // Vx = Vy, if the sum is greater than 255, then VF = 1
void SUB_8xy5(); // Vx -= Vy, if Vx > Vy, then VF = 1, otherwise VF = 0
void SHR_8xy6(); // Vx >>= 1, if least significant bit of Vx is 1, then VF is set to 1, otherwise 0
void SUBN_8xy7(); // Vx = Vy - Vx, if Vy > Vx, VF = 1, otherwise VF = 0
void SHL_8xyE(); // Vx <<= 1, if most significant bit of Vx is 1, then VF is set to 1, otherwise 0
void SNE_9xy0(); // Skip next instruction if Vx != Vy
void LD_Annn(); // I = nnn
void JP_Bnnn(); // Jumps to nnn V0
void RND_Cxkk(); // Vx = random byte & kk
void DRW_Dxyn(); // Draws n-byte (n = height) sprite starting at Vx and Vy. If collision detected, VF = 1
void SKP_Ex9E(); // Skip next instruction if value of Vx is pressed
void SKNP_ExA1(); // Skip next instruction if value of Vx isn't pressed
void LD_Fx07(); // Set Vx = delay timer
void LD_Fx0A(); // Wait for key press and store value in Vx
void LD_Fx15(); // Set delay timer = Vx
void LD_Fx18(); // Set sound timer = Vx
void ADD_Fx1E(); // Set I = Vx
void LD_Fx29(); // Set I = memory location of digit sprite in Vx
void LD_Fx33(); // Store BCD representation of value of Vx in I, I 1, I 2
void LD_Fx55(); // Store registers V0 through Vx (including) starting at memory location I
void LD_Fx65(); // Read registers V0 through Vx (including) starting at memory location I
有什么問題，我該如何解決？
uj5u.com熱心網友回復：
問題是當你寫：
static void (*table[16])();
您正在宣告一個名為的靜態資料成員table，它是一個大小陣列，16其元素是指向沒有引數且回傳型別為 int的自由函式的指標。
但是您真正想要的是一個table大小陣列，16其元素是指向成員函式的Chip8指標，您可以執行以下操作：
class Chip8{
private:
//---------------vvvvvvvv------------>note the added Chip8::* indicating that a pointer to a member function instead of free function
static void (Chip8::*table[16])(); //function pointer table
public:
void cycle();
void opcode0();
};
//definition for the static data member `table`
void (Chip8::*Chip8::table[16])() = {
&Chip8::opcode0,
};
void Chip8::opcode0()
{
std::cout<<"opcode0 called"<<std::endl;
}
void Chip8::cycle(){
std::cout<<"cycle called"<<std::endl;
(this->*table[0])();
}
int main()
{
Chip8 chip;
chip.cycle();
return 0;
}
作業演示。
請注意，您可以使用別名宣告使上述代碼更具可讀性，如下所示：
class Chip8{
private:
using type = void (Chip8::*)();
static type table[16]; //function pointer table
public:
void cycle();
void opcode0();
};
Chip8::type Chip8::table[16] = {
&Chip8::opcode0,
};
void Chip8::opcode0()
{
std::cout<<"opcode0 called"<<std::endl;
}
void Chip8::cycle(){
std::cout<<"cycle called"<<std::endl;
(this->*table[0])();
}
int main()
{
Chip8 chip;
chip.cycle();
return 0;
}
演示
uj5u.com熱心網友回復：
您的表包含函式指標，而不是成員函式指標。只需將它們用作沒有this.
我的猜測是分配給表的所有函式都是靜態函式。
對于非靜態函式，使用表的成員函式指標型別：
static void (Chip::*table[16])(); // member function pointer table
或更具可讀性：
using OpType = void (Chip::*)();
static OpType table[16];
轉載請註明出處，本文鏈接：https://www.uj5u.com/yidong/470844.html